Les Goring - Manual of First and Second Fixing Carpentry (pdf, 10642 Кб)

Les Goring - Manual of First and Second Fixing Carpentry (pdf, 10642 Кб)
Manual of First &
Second Fixing Carpentry
Second Edition
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Manual of First &
Second Fixing Carpentry
Second Edition
Les Goring FIOC, LCG, FTC
Associate of the Chartered Institute of Building
Former Senior Lecturer in Wood Trades at Hastings College of Arts and Technology
Drawings by the author
AMSTERDAM • BOSTON • HEIDELBERG • LONDON • NEW YORK • OXFORD
PARIS • SAN DIEGO • SAN FRANCISCO • SINGAPORE • SYDNEY • TOKYO
Butterworth-Heinemann is an imprint of Elsevier Ltd
Linacre House, Jordan Hill, Oxford OX2 8DP
30 Corporate Road, Burlington, MA 01803
First edition 1998
Reprinted 2000, 2002, 2003, 2004 (twice) 2005
Second edition 2007
Copyright © 2007, Les Goring. Published by Elsevier Limited. All rights reserved
The right of Les Goring to be identified as the author of this work has been asserted in accordance
with the Copyright, Designs and Patents Act 1988
No part of this publication may be reproduced, stored in a retrieval system or transmitted in any form or
by any means electronic, mechanical, photocopying, recording or otherwise without the prior written
permission of the publisher
Permission may be sought directly from Elsevier’s Science & Technology Rights Department in Oxford,
UK: phone (⫹44) (0) 1865 843830; fax (⫹44) (0) 1865 853333; email: [email protected]
Alternatively you can submit your request online by visiting the Elsevier web site at
http://elsevier.com/locate/permissions, and selecting Obtaining permission to use Elsevier material
Notice
No responsibility is assumed by the publisher for any injury and/or damage to persons or property
as a matter of products liability, negligence or otherwise, or from any use or operation of any methods,
products, instructions or ideas contained in the material herein. Because of rapid advances in the
medical sciences, in particular, independent verification of diagnoses and drug dosages should be made
British Library Cataloguing in Publication Data
A catalogue record for this book is available from the British Library
Library of Congress Cataloguing in Publication Data
A catalogue record for this book is available from the Library of Congress
ISBN: 978-0-75-068115-5
For information on all Butterworth-Heinemann publications
visit our website at www.books.elsevier.com
Typeset by Charon Tec Ltd (A Macmillan Company), Chennai, India
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Printed and bound in the UK
07 08 09 10 11 10 9 8 7 6 5 4 3 2 1
To Mary, Penny, Jon and Jenny, and other Gorings
of whom there are many
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Contents
Preface
Acknowledgements
Abbreviations
Technical Data
1
2
xiii
xiv
xv
xvi
Reading Construction Drawings
1
1.1
1.2
1.3
1
3
5
Introduction
Orthographic Projection
Oblique Projections
Tools Required: their Care and Proper Use
2.1
2.2
2.3
2.4
2.5
2.6
2.7
2.8
2.9
2.10
2.11
2.12
2.13
2.14
2.15
2.16
2.17
2.18
2.19
2.20
Introduction
Marking and Measuring
Handsaws
Hammers
Screwdrivers
Marking Gauges
Chisels
Oilstones and Diamond Whetstones
Hand Planes
Ratchet Brace
Bits and Drills
Individual Handtools
Portable Powered and Cordless Circular Saws
Powered and Cordless Drills and Screwdrivers
Powered and Cordless Planers
Powered and Cordless Jigsaws
Powered and Cordless SDS Rotary Hammer Drills
Powered (Portable) Routers
Jigs
Nailing Guns
8
8
8
12
15
16
16
17
18
19
20
20
23
24
25
26
27
28
28
29
30
viii
Contents
3
Carpentry Fixing-Devices
34
3.1
3.2
3.3
3.4
34
34
36
40
4
5
6
7
8
Introduction
Nails and Pins
Screws and Plugs
Cavity Fixings
Making a Carpenter’s Tool Box
41
4.1
4.2
41
41
Introduction
Construction
Making Builder’s Plant for Site Use
45
5.1
5.2
5.3
5.4
5.5
5.6
5.7
45
53
54
55
56
58
59
Saw Stool
Nail Boxes
Hop-ups
Board and Stand
Builder’s Square
Straightedges and Concrete-levelling Boards
Plumb Rules
Fixing Door Frames, Linings and Doorsets
60
6.1
6.2
6.3
6.4
6.5
6.6
6.7
6.8
6.9
6.10
6.11
60
62
64
65
68
69
69
70
70
71
72
Introduction
Fixing Door Frames
Frame Detail
Fixing Door Linings
Setting Up Internal Frames Prior to Building Block-partitions
Storey Frames
Subframes
Built-up Linings
Moisture Effect from Wet Plastering Methods
Doorsets
Fire-resisting Doorsets
Fixing Wooden and uPVC Windows
74
7.1
7.2
7.3
7.4
7.5
74
74
75
76
78
Introduction
Casement Windows
Glazing
Window Boards
Boxframe Windows
Fixing Floor Joists and Flooring
80
8.1
8.2
80
81
Introduction
Ground Floors
Contents
8.3
8.4
8.5
8.6
8.7
8.8
8.9
8.10
8.11
8.12
8.13
8.14
8.15
9
Laying T&G Timber Boarding
Floating Floor (with Continuous Support)
Floating Floor (with Discontinuous Support)
Fillet or Battened Floors
Beam-and-Block Floor
Engineered-Timber Floors
Upper Floors
Strutting
Fitting and Fixing Timber Joists
Fixing Flooring Panels on Joists
Fitting and Fixing Engineered Joists
Posi-Joist™ Steel-Web System
Overlay Flooring
ix
84
85
85
86
87
87
88
91
94
94
95
98
101
Fixing Interior and Exterior Timber Grounds
104
9.1
9.2
9.3
9.4
9.5
9.6
9.7
104
104
105
105
105
106
106
Introduction
Skirting Grounds
Architrave Grounds
Apron-lining Grounds
Wall-panelling Grounds
Framed Grounds
External Grounds
10 Fixing Stairs and Balustrades
10.1
10.2
10.3
10.4
Introduction
Installation Procedure
Fixing Tapered Steps
Fixing Balustrades
11 Stair Regulations Guide to Design and Construction
11.1 The Building Regulations 2000
12 Constructing Traditional and Modern Roofs
12.1
12.2
12.3
12.4
12.5
12.6
12.7
12.8
12.9
Introduction
Basic Roof Designs
Roof Components and Terminology
Basic Setting-out Terms
Geometrical Setting-out of a Hipped Roof
Roofing Ready Reckoner
Metric Rafter Square
Alternative Method for the Use of the Metric Rafter Square
Bevel-formulas for Roofing Square
107
107
108
116
118
122
122
131
131
132
132
138
140
141
143
144
146
x
Contents
12.10
12.11
12.12
12.13
12.14
12.15
12.16
12.17
12.18
12.19
12.20
12.21
12.22
12.23
12.24
12.25
12.26
12.27
12.28
12.29
12.30
12.31
12.32
12.33
Roofmaster Square
Setting Out a Common (Pattern) Rafter
Setting Out a Crown (or Pin) Rafter
Setting Out a Hip Rafter
Setting Out Jack Rafters
Pitching Details and Sequence
Pitching a Hipped Roof (Double-ended)
Flat Roofs
Dormer Windows and Skylights
Skylights (Roof Windows)
Eyebrow Windows
Lean-to Roofs
Chimney-trimming and Back Gutters
Trussed Rafters
Erection Details and Sequence for Gable Roofs
Hipped Roofs Under 6 m Span
Hipped Roofs Over 6 m Span
Alternative Hipped Roof up to 11 m Span
Valley Junctions
Gable Ladders
Roof Hatch (Trap)
Chimney Trimming
Water-Tank Supports
Work at Height Regulations 2005
13 Erecting Timber Stud Partitions
13.1
13.2
13.3
13.4
13.5
13.6
13.7
13.8
13.9
Introduction
Traditional Braced Partition
Traditional Trussed Partition
Modern Stud Partition
Door-stud and Door-head Joints
Stud Joints to Sill and Head Plate
Door-stud and Sill-plate Joints
Corner and Doorway Junctions
Floor and Ceiling Junctions
14 Geometry for Arch Shapes
14.1
14.2
14.3
14.4
14.5
Introduction
Basic Definitions
Basic Techniques
True Semi-elliptical Arches
Approximate Semi-elliptical Arches
147
150
151
152
155
156
159
160
164
168
168
174
174
175
177
177
178
178
179
179
180
180
181
182
183
183
183
183
184
186
187
188
189
190
193
193
193
194
196
198
Contents
14.6
14.7
14.8
14.9
Gothic Arches
Tudor Arches
Parabolic Arches
Hyperbolic Arch
15 Making and Fixing Arch Centres
15.1
15.2
15.3
15.4
15.5
15.6
Introduction
Solid Turning Piece (Single-rib)
Single-rib Centres
Twin-rib Centres
Four-rib Centres
Multi-rib Centres
16 Fixing Architraves, Skirting, Dado and Picture Rails
16.1 Architraves
16.2 Skirting
16.3 Dado Rails and Picture Rails
xi
199
199
201
201
203
203
203
204
205
206
208
210
210
214
217
17 Fitting and Hanging Doors
218
17.1 Introduction
17.2 Fitting Procedure
17.3 Hanging Procedure
218
218
223
18 Fitting Locks, Latches and Door Furniture
18.1
18.2
18.3
18.4
18.5
18.6
18.7
18.8
Locks and Latches
Mortice Locks
Mortice Latches
Mortice Dead Locks
Cylinder Night Latches
Fitting a Letter Plate
Fitting a Mortice Lock
Fitting Door Furniture
19 Fixing Pipe Casings and Framed Ducts
19.1 Introduction
19.2 Pipe Casings
19.3 Framed Ducts
20 Designing and Installing a Fitted Kitchen
20.1 Introduction
20.2 Ergonomic Design Considerations
20.3 Planning the Layout
224
224
224
225
226
226
226
227
228
229
229
229
229
230
230
230
231
xii
Contents
20.4
20.5
20.6
20.7
20.8
20.9
Dismantling the Old Kitchen
Pre-fitting Preparation
Fitting and Fixing Base Units
Cutting, Jointing and Fitting Worktops
Fixing the Wall Units
Adding Finishing Items
21 Site Levelling and Setting Out
21.1 Introduction
21.2 Establishing a Datum Level
21.3 Setting Out the Shape and Position of the Building
Appendix: Glossary of Terms
Index
232
233
234
235
237
238
239
239
239
240
245
251
Preface
This book was written because there is a need for
trade books with a strong practical bias, using a DIY
step-by-step approach – and not because there was
any desire to add yet another book to the long list of
carpentry books already on the market. Although
many of these do their authors credit, the bias is
mainly from a technical viewpoint with wide general
coverage and I believe there is a potential market for
books (manuals) that deal with the sequence and techniques of performing the various, unmixed specialisms
of the trade. Such is the aim of this book, to present a
practical guide through the first two of these subjects,
namely first-fixing and second-fixing carpentry.
These definitions mean that any work required to
be done before plastering takes place – such as roofing
and floor joisting – is referred to as first-fixing carpentry; second-fixing carpentry, therefore, refers to any
work that takes place after plastering – such as fixing
skirting boards, architraves and door-hanging.
Most carpenters cover both areas of this work,
although some specialize in either one or the
other. To clarify the mix up between carpentry and
joinery, items of joinery – such as staircases and
wooden windows – are manufactured in workshops
and factories and should be regarded as a separate
specialism.
The book, hopefully, will be of interest to many
people, but it was written primarily for craft apprentices (a rare breed in this present-day economy),
trainees and building students, established tradespeople, seeking to reinforce certain weak or sketchy
areas in their knowledge and, as works of reference,
the book may also be of value to vocational teachers,
lecturers and instructors. Finally, the sequential,
detailed treatment of the work should appeal to the
keen DIY enthusiast.
Les Goring
Acknowledgements
The author would like to thank the following people
and companies for their co-operation in supplying
technical literature or other assistance used in either
the first edition, or in this, the revised edition of the
book. Special thanks go to Jenny Goring, Jonathan
Goring, Kevin Hodger, Peter Shaw and Tony Moon,
who assisted on both occasions:
Alpha Pneumatic Supplies Ltd, Unit 7, Hatfield
Business Park, Hatfield, Hertfordshire AL10 9EW,
UK (www.nailers.co.uk) for information on air nailers
and compressors; Andrew Thomas and Ian Harris of
ITW (Illinois Tool Works) Construction Products
(www.itwcp.co.uk); Brian Redfearn of Hastings
College; CSC Forest Products Limited (OSB flooring
panels); Dave Aspinall and Ronni Boss of Hilti GB
Ltd (www.hilti.co.uk); Doris Funke, Commissioning
Editor, Elsevier Limited; Eric Brown and Bradley
Cameron of DuPont™ Tyvek®, Hither Green Trading
Estate, Clevedon, North Somerset BS21 6XU
(www.tyvekhome.com); Gang-Nail Systems Ltd, a
member company of the International Truss Plate
Association; Health and Safety Executive (HSE), for
the Work at Height Regulations 2005; Helen Eaton,
Editorial Assistant, Elsevier Limited; Jenny, my
daughter, for meticulously collating and compiling the
original Index and the amended Index to this edition;
Kevin Hodger, ex colleague (inventor of the
Roofmaster Square); Kieran Damani of House of
Hastings Ltd, Queen’s Road, Hastings; Kingsview
Optical Ltd (suppliers of the Roofmaster Square)
Harbour Road, Rye, East Sussex TN31 7TE, UK,
telephone ⫹44 (0) 1797 226202; Laybond Products
Ltd; Mark Kenward, MRICS, extraordinary carpentry
student, now a qualified surveyor; McArthur Group
Ltd, for their DVD catalogue on nails and screws, etc
(www.mcarthur-group.com); Melvyn Batehup (for his
suggested revision-areas); Mark Bond, manager of
MFI (UK) Ltd, Branch 183, Hastings, East Sussex;
Mike Owst, Programme Area Leader in Construction
Studies at Hastings College; Mike Willard of Bexhill
Locksmiths & Alarms; Pace Timber Engineering Ltd,
Bleak Hall, Milton Keynes MK6 1LA (www.pacetimber.co.uk); Paul Stillwell of House of Hastings; Percy
Eldridge, former lecturer at Hastings College; Peter
Bullock of MiTeK Industries Ltd (re MiTek PosiJoist™ Steel Web System), Grazebrook Industrial
Park, Peartree Lane, Dudley DY2 OXW
(www.mitek.co.uk); Peter Oldfield and Peter Shaw of
Hastings College; Rachel Hudson, Commissioning
Editor (Newnes), Butterworth-Heinemann (for
prompting a definition of 1st- and 2nd-fixing carpentry in the preface); Schauman (UK) Ltd (plywood
flooring panels); South Coast Roofing Supplies Ltd,
St Leonards-on-Sea; Steve Pearce of South Coastal
Windows and Doors (uPVC) Ltd; Sydney Clarke of
Helifix Ltd; Tony Fleming, former Head of
Construction Studies at Hastings College; Tony
Moon of A & M Architectural Design Consultants,
Hastings, East Sussex (01424 200222); Toolbank of
Dartford, Kent, for information from their 2006/7
‘Big Blue book’ on tools and accessories (www.toolbank.com); Trus Joist™, East Barn, Perry Mill Farm,
Birmingham Road, (A441), Hopwood,
Worcestershire B48 7AJ, UK (www.trustjoist.com);
York Survey Supply Centre (www.YorkSurvey.co.uk);
and the last two important contributors: Jonathan, my
son, for patiently posing with his hands for the original illustration at Figure 2.26 in chapter two and for
turning me on to word processing prior to rewriting
this book, via his gift of a laptop – and Darren
Eglington, my son-outof-law, for his time and
patience in teaching me how to use it.
Abbreviations
bdg
bldg
BMA
BS
c/c
C
L
cpd
DPC
DPM
dia, ø
EML
ex.
ffl
boarding
building
bronze metal antique
British Standards (Institution)
centre to centre (measurement)
centre line
cupboard
damp-proof course
damp-proof membrane
diameter
expanded metal lathing
prefix to material size before being worked
finished floor level
GL
hdb
hwd
ms
O/A
par
ppd
PVA
swd
T&G
TRADA
vh
ground level
hardboard
hardwood
mild steel
over all (measurement)
planed all round
prepared (timber planed all round)
polyvinyl acetate (adhesive)
softwood
tongued and grooved
Timber Research and Development
Association
vertical height
Technical Data
STANDARD TIMBER-SIZES
Table 1 shows the basic sectional sizes for sawn softwood recommended by the British Standards to be
available to the industry – it should be borne in mind
that any non-standard requirement represents a special order and is likely to cost more.
Standard metric lengths are based on a 300 mm
module, starting at 1.8 m and increasing by 0.3 m
to 2.1 m, 2.4 m, 2.7 m and so on, up to 6.3 m.
Non-standard lengths above this, usually from North
American species, may be obtained up to about 7.2 m.
For anybody more used to working in imperial sizes
rather than metric, it is worth bearing in mind that
measured pieces of timber required for a particular
job, must be divisible by 0.3 to meet the modular
sizes available. For instance, 3.468 m ⫼ 0.3 ⫽ 11.56
modules. Therefore, this would have to be increased
commercially to 12 modules, i.e., 12 ⫻ 0.3 ⫽ 3.6 m,
which is a commercially available size. If you
prefer, you can think of this little sum as 12 ⫻
3 ⫽ 36, then insert the decimal point. This simple
mental arithmetic, based on the three-times-table,
can be used for all the commercially available sizes
between 6 ⫻ 3 ⫽ 18 (1.8 m) and 21 ⫻ 3 ⫽ 63
(6.3 m).
Table 1 Sawn structural timber sizes (From BS 336: 1995)
mm
inches
75
100
125
150
175
200
225
250
275
300
3
4
5
6
7
8
9
10
11
12
✓
✓
✓
✓
✓
✓
22
–87
25
38
1
1 –12
✓
✓
✓
✓
✓
✓
✓
✓
✓
✓
✓
✓
✓
✓
47
1 –87
✓
✓
✓
✓
✓
✓
✓
✓
63
75
100
150
250
300
2 –12
✓
✓
✓
✓
✓
✓
✓
✓
✓
✓
✓
✓
✓
✓
✓
✓
✓
✓
✓
✓
3
4
6
10
12
✓
✓
✓
✓
✓
✓
✓
Technical Data
xvii
STANDARD DOOR-SIZES
Door frames and linings may vary in their opening
sizes, but are normally made to accommodate standard doors. Again, it must be realized that special
doors, made to fit non-standard frames or linings,
would considerably increase the cost of the job. The
locations given to the groups of standard door-sizes in
Table 2, below, are only a guide, not a fixed rule.
Table 2 Standard doors and their usual location
Metric
Imperial
Height (m)
Width (mm)
Thickness (mm)
Height (ft/in)
Width (ft/in)
Thickness (in)
Main entrance
doors
2.134
2.083
2.032
1.981
1.981
914
864
813
838
762
45
45
45
45
45
7⬘0⬙
6⬘10⬙
6⬘8⬙
6⬘6⬙
6⬘6⬙
3⬘0⬙
2⬘10⬙
2⬘8⬙
2⬘9⬙
2⬘6⬙
1 –34
1 –34
1 –34
1 –34
1 –34
Room doors
2.032
1.981
813
762
45 or 35
45 or 35
6⬘8⬙
6⬘6⬙
2⬘8⬙
2⬘6⬙
1 –34 or 1 –38
1 –34 or 1 –38
Bathroom/toilet
doors
1.981
1.981
762 or 711
686
35
35
6⬘6⬙
6⬘6⬙
2⬘6⬙ or 2⬘4⬙
2⬘3⬙
1 –38
1 –38
Cupboard doors
1.981
1.981
1.981
610
533
457
35
35
35
6⬘6⬙
6⬘6⬙
6⬘6⬙
2⬘0⬙
1⬘9⬙
1⬘6⬙
1 –38
1 –38
1 –38
Note: When door frames and doors are required to be fire-resisting, special criteria laid down by the British Standards Institution
and The Building Regulations must be adhered to – a detailed reference to this is given in Chapter 6.
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1
Reading Construction
Drawings
1.1 INTRODUCTION
1.1.1 Retention of Drawings or
Sketches
Construction drawings are necessary in most spheres
of the building industry, as being the best means of
conveying detailed and often complex information
from the designer to all those concerned with the job.
Building tradespeople, especially carpenters and joiners, should be familiar with the basic principles
involved in understanding and reading drawings correctly. Mistakes on either side – in design or interpretation of the design – can be costly, as drawings form a
legal part of the contract between architect/client and
builder. This applies even on small jobs, where only
goodwill may suffer; for this reason, if a non-contractual
drawing or sketch is supplied, it should be kept for a
period of time after completion of the job, in case any
queries should arise.
A simple sketch supplied by a client in good faith to a
builder or joinery shop for the production of a replacement casement-type window, is shown in Figure 1.1(a).
The client’s mistake in measuring between plastered
reveals is illustrated in Figure 1.1(b). Retention of the
sketch protects the firm from the possibility of the
client’s wrongful accusation.
Another important rule is to study the whole drawing carefully and be reasonably familiar with the
details before starting work.
The details given in this chapter are based on the
recommendations laid down by the British Standards
Institution, in their latest available publications entitled
Construction drawing practice, BS 1192: Part 1: 1984,
and BS 1192: Part 3: 1987. BS 1192: Part 5: 1990,
which is not referred to here, is a guide for the structuring of computer graphic information.
F
1100
300
950
(a)
950
(b)
Figure 1.1 (a) Client’s sketch drawing.
(b) Horizontal section showing client’s
mistake
2
Reading Construction Drawings
1:100
0
1:50
0
1:20
500
250
1m
500
500
750
2
1m
300
100
3
250
500
500
4
750
2m
700
5m
250
500
900
0
1:10
1m
50
100
25
50
200
300
400
500 mm
0
1:5
75
100
200 mm
0
1.1.2 Scales Used on Drawings
Parts of metric scale rules, graduated in millimetres, are
illustrated in Figure 1.2. Each scale represents a ratio of
given units (millimetres) to one unit (one millimetre).
Common scales are 1:100, 1:50, 1:20, 1:10, 1:5 and 1:1
(full size). For example, scale 1:5 ⫽ one-fifth (-51) full
size, or 1 mm on the drawing equals 5 mm in reality.
Although a scale rule is useful when reading drawings, because of the dimensional instability of paper,
preference should always be given to written dimensions found on the drawing.
1.1.3 Correct Expressions of
Dimensions
The abbreviated expression, or unit symbol, for metres is
a small letter m, and letters mm for millimetres. Symbols
are not finalized by a full stop and do not use a letter ‘s’
for the plural. Confusion occurs when, for example, 3-12
metres is written as 3.500 mm – which means, by virtue
of the decimal point in relation to the unit symbol, 3-12
millimetres! To express 3-12 metres, it should have been
written as 3500 mm, 3.5 m, 3.50 m, or 3.500 m. Either
one symbol or the other should be used throughout on
drawings; they should not be mixed. Normally, whole
numbers should indicate millimetres, and decimalized
numbers, to three places of decimals, should indicate
metres. Contrary to what is taught in schools, the construction industry in the UK does not use centimetres.
All references to measurement are made in millimetres
and/or metres, i.e. 2 cm should be expressed as 20 mm.
1.1.4 Sequence of Dimensioning
The recommended dimensioning sequence is illustrated in Figure 1.3. Length should always be given
first, width second and thickness third, for example
Figure 1.2 Common metric scales
B
A
C
Figure 1.3 Dimensioning sequence ⫽ A ⫻ B ⫻ C
900 ⫻ 200 ⫻ 25 mm. However, if a different sequence
is used, it should be consistent throughout.
1.1.5 Dimension Lines and Figures
A dimension line with open arrowheads for basic/
modular (unfinished) distances, spaces or components
is indicated in Figure 1.4(a). Figure 1.4(b) indicates the
more common, preferred dimension lines, with solid
arrowheads, for general use in finished work sizes.
All dimension figures should be written above and
along the line; figures on vertical lines should be written, as shown, to be read from the right-hand side.
1.1.6 Special-purpose Lines
Figure 1.5: Section lines seen on drawings indicate
imaginary cutting planes, at a particular point through
the drawn object, to be exposed to view. The view is
called the section and is lettered A–A, B–B and so on,
according to the number of sections to be exposed. It
is important to bear in mind that the arrows indicate
the direction of view to be seen on a separate section
drawing.
Orthographic Projection
Figure 1.4 Dimension lines.
(a) Open arrow-head (unfinished).
(b) Solid arrow-head (finished)
300
(a)
200
323
(b)
C
A
A
B
B
3
D
E
C
D
Vertical sections
Horizontal sections
Staggered section
E
Figure 1.5 Section lines
Figure 1.6 Hidden detail or work to be
removed
Figure 1.6: Hidden detail or work to be removed, is
indicated by a broken line.
1.300
(a)
(b)
Figure 1.7(a): End break-lines (zig-zag pattern) indicate that the object is not fully drawn.
Figure 1.7 Break lines
Figure 1.7(b): Central break-lines (zig-zag pattern)
indicate that the object is not drawn to scale in length.
Figure 1.8 Centre or axial line
Figure 1.8: Centre or axial lines are indicated by a thin
dot-dash chain.
1.2 ORTHOGRAPHIC
PROJECTION
1.2.1 Introduction
Orthography is a Latin/Greek-derived word meaning
‘correct spelling’ or ‘writing’. In technical drawing it is
used to mean ‘correct drawing’; orthographic projection, therefore, refers to a conventional drawing
method used to display the three-dimensional views
(length, width and height) of objects or arrangements
as they will be seen on one plane – namely the drawing surface.
The recommended methods are known as firstangle (or European) projection for construction drawings, and third-angle (or American) projection for
engineering drawings.
1.2.2 First-angle Projection
The box in Figure 1.9(a) is used here as a means of
explaining first-angle projection (F.A.P.). If you can
imagine the object shown in Figure 1.9(b) to be suspended in the box, with enough room left for you to
walk around it, then by looking squarely at the object
from all sides and from above, the views seen would be
the ones shown on the surfaces in the background.
1.2.3 Opening the Topless Box
In Figure 1.9(c) the topless box is opened out to give
the views as you saw them in the box and as they
should be laid out on a drawing. Figure 1.9(d) shows
the BS symbol recommended for display on drawings
to indicate that first-angle projection (F.A.P.) has been
used.
Note that when views are separated onto different
drawings, becoming unrelated orthographically,
descriptive captions should be used such as ‘plan’,
‘front elevation’, ‘side elevation’, etc.
4
Reading Construction Drawings
Vertical planes
FE
FE
SE.L/H
SE.R/H
RE
SE.L/H
SE
RE
Plan
Front
Plan
Horizontal plane
Figure 1.9 (a) Theory of first-angle orthographic
projection (SE ⫽ side elevation, FE ⫽ front elevation,
RE ⫽ rear elevation, R/H ⫽ right-hand side, L/H ⫽ lefthand side)
Side elevation R/H
Front elevation
Figure 1.9 (b) Example object
Side elevation L/H
Rear elevation
Vertical planes
Horizontal plane
Plan
Figure 1.9 (c) First-angle projection
Figure 1.9 (d) F.A.P. symbol
Horizontal plane
Vertical planes
Plan
Side elevation L/H
Front elevation
Figure 1.9 (e) Third-angle projection
Side elevation R/H
Rear elevation
Side
Oblique Projections
5
1.3 OBLIQUE PROJECTIONS
There are three variations of oblique projections.
1.3.1 Cavalier Projection
Figure 1.9 (f) T.A.P. symbol
1.2.4 Third-angle Projection
Shown in Figure 1.10(b) with front (F) drawn true to
shape, and side (S) elevations and plan (P) drawn at
45⬚, to a ratio of 1:1:1. Drawn true to scale by this
method, the object tends to look mis-shapen.
This is shown in Figure 1.9(e) for comparison only. This
time the box has a top instead of a bottom; the views
from the front and rear would be shown on the surface
in the background, as before, but the views seen on the
sides would be turned around and seen on the surfaces in
the foreground; the view from above (plan) would be
turned and seen on the surface above. Figure 1.9(f )
shows the BS symbol for third-angle projection (T.A.P.).
Shown in Figure 1.10(c), this is similar to cavalier
except that the side and plan projections are only
drawn to half scale, i.e. to a ratio of 1:1:-12, making the
object look more natural.
1.2.5 Pictorial Projections
1.3.3 Planometric Projection
Figure 1.10: Another form of orthographic projection
produces what is known as pictorial projections, which
preserve the three-dimensional view of the object.
Such views have a limited value in the make-up of
actual working drawings, but serve well graphically to
illustrate technical notes and explanations.
Shown in Figure 1.10(d), this has the plan drawn true
to shape, instead of the front view. This comprises verticals, lines on the front at 30º and lines on the side
elevation at 60º. It is often wrongly referred to as
axonometric.
1.3.4 Perspective Projections
1.2.6 Isometric Projection
This is probably the most popular pictorial projection
used, because of the balanced, three-dimensional
effect. Isometric projections consist of vertical lines and
base lines drawn at 30⬚, as shown in Figure 1.10(a).
The length, width and height of an object thus drawn
are to true scale, expressed as the ratio 1:1:1.
1
1
30°
1
1
30°
1
(a) Isometric
Figure 1.11: Parallel perspective, shown in Figure
1.11(a) refers to objects drawn to diminish in depth to
a vanishing point.
Angular perspective, shown in Figure 1.11(b) refers
to an object whose elevations are drawn to diminish
to two vanishing points. This is of no value in pure
technical drawing.
1
1
45°
1
1
—
2
45°
1
1
1
30°
60°
P
P
F
1.3.2 Cabinet Projection
P
P
S
S
F
F
(b) Cavalier
(c) Cabinet
Figure 1.10 Pictorial projections (F ⫽ front, P ⫽ plan, S ⫽ side elevation)
S
F
S
(d) Planometric
6
Reading Construction Drawings
VP
VP
(a) Parallel perspective
VP
(b) Angular perspective
Figure 1.11 Perspective projections (VP ⫽ vanishing point)
1.3.5 Graphical Symbols and
Representation
Figure 1.12: Illustrated here are a selection of graphical symbols and representations used on building
drawings.
Figure 1.13: On more detailed drawings, various
materials and elements are identified by such sectional
representation as shown here.
To help reduce the amount of written information
on working drawings, abbreviations are often used.
A selection are shown here:
BMA ⫽ bronze metal antique
DPC ⫽ damp-proof course
DPM ⫽ damp-proof membrane
= Rise of stair
= Rise of ramp
dia (or Ø) = Diameter
CL
= Centre line
ffl
= Finished floor level
GL
= Ground level
c/c
= Centre to centre
= North point
Figure 1.12 Graphical symbols and representations
EML ⫽ expanded metal lathing
par ⫽ planed all round
PVA ⫽ polyvinyl acetate
T&G ⫽ tongue and groove
bdg ⫽ boarding
bldg ⫽ building
cpd ⫽ cupboard
hbd ⫽ hardboard
hwd ⫽ hardwood
ms ⫽ mild steel
swd ⫽ softwood
1.3.6 Window Indication
Figure 1.14: Windows shown on elevational drawings
usually display indications as to whether a window is
fixed (meaning without any opening window or vent)
Brickwork
Topsoil
Blockwork
Stone
Concrete
Hardcore
Plywood
Wood (sawn)
Subsoil
Insulation
Screed/plaster/render
Wood (planed)
Figure 1.13 Sectional representation of materials
W2
Top hung
W8
Horizontal
pivot
W7
Vertical
pivot
W6
Sliding
W5
W4
Fixed
Sliding
W3
Bottom hung
W1
Side hung
W9
Tilt and turn
Figure 1.14 Opening/fixed window indication – numbered clockwise round the exterior of the building
Oblique Projections
Sliding door
Single swing
7
Double doors
single swing
Single door
double swing
Double doors
double swing
Figure 1.15 Plan view of door indication
or opening (meaning that the window is to open in a
particular way, according to the BS indication drawn
on the glass area).
1.3.7 Door Indication
Figure 1.16 Revolving doors
1.3.9 Site Plans
Figure 1.18: Site plans locate the position of buildings
in relation to setting-out points, means of access, and
the general layout of the site; they also give information on services and drainage, etc.
MH2
Figure 1.17: Block plans shown on construction drawings, usually taken from Ordinance Survey maps, are to
identify the site (e.g. No. 1 Woodman Road, as illustrated) and to locate the outline of the building in
relation to its surroundings.
G
1.500
11
MH3
SVP
G
NO 1
WOODMAN
ROAD
G
13 15
MH1
6.250
WOOD
MAN
5.600
1 3
ROAD
1.3.8 Block Plans
8.750
Figures 1.15 and 1.16: Doors shown on plan-view
drawings are usually shown as a single line with an
arrowed arc indicating their opening-direction, as
illustrated. Alternatively, the 90⬚ arrowed arc may be
replaced by a 45⬚ diagonal line, from the door-jamb’s
edge to the door’s leading edge. Figure 1.16 is the
indication for revolving doors.
LOFTS
45 47
ROAD
14
Figure 1.18 Site plan (scale 1:200)
1.3.10 Location Drawings
Figure 1.17 Block plan (scale 1:1250)
These are usually drawn to a scale of 1:50 and are used
to portray the basic, general construction of buildings.
Other, more detailed, drawings cover all other aspects.
2
Tools Required: their Care
and Proper Use
2.1 INTRODUCTION
The whole range of tools for first- and second-fixing
carpentry is quite extensive and includes power and
battery-operated (cordless) tools in the essential list.
The following details, therefore, do not cover all the
tools that you could have, rather all the tools that you
should have.
rectangular-shaped carpenters’ pencils (Figure 2.1(c)),
of a soft or medium grade lead, are better for heavy
work such as roofing, joisting, marking unplaned timber, etc. – although one disadvantage is that they cannot be put behind the ear for quick availability, as is
the usual practice with ordinary pencils.
2.2.2 Tape Rule
2.2 MARKING AND
MEASURING
3.5 m
2.2.1 Pencils
Figure 2.2 Tape rule
Figure 2.1: These must be kept sharp for accurate
marking. Although sharpening to a pin-point is quite
common, for more accurate marking and a longerlasting point, they can easily be sharpened to a chiselpoint, similar to the sharpening illustrated in Figure
2.1(c). Stumpy sharpening (Figure 2.1(a)) should be
avoided; sharpen at an angle of about 10⬚ (Figure
2.1(b)). Use grade HB for soft, black lines on
unplaned timber and – if you prefer – grade 2H on
planed timber. Choose a hexagon shape for better grip
and anti-roll action, and a bright colour to detect
easily when left lying amongst shavings. Oval or
Figure 2.2: This is essential for fast, efficient measuring on site work. For this type of carrying-rule, sizes
vary between 2 m and 10 m. Models with lockable,
power-return blades and belt clips, one of 3.5 m and
one of 8 m length are recommended. When retracting
these power-return rules, slow down the last part of
the blade with the sliding lock to avoid damaging the
riveted metal hook at the end or nipping your fingers.
To reduce the risk of kinking the sprung-steel blade,
do not leave extended after use.
2.2.3 Folding Rule
(a)
(b)
(c)
Figure 2.1 Pencils
Figure 2.3: This rule is optional, having been superseded by the tape rule. However, it is sometimes
preferred for measuring/marking small sizes. Its
unfolded length is 1 m and it is 250 mm folded. It is
marked in single millimetre, 5 mm, 10 mm (centimetre)
and 100 mm (decimetre) graduations. It is still available
in boxwood or – better still – in virtually unbreakable
white or grey engineering plastic with tipped ends, permanently tensioned joints and bevelled edges for easier,
more accurate reading/marking when the rule is laid
out flat. These rules, although tough, should always be
Marking and Measuring
9
Elevation
Figure 2.3 Folding rule
Plan
folded after use to avoid possible hinge damage, especially from underfoot if left on the floor.
2.2.4 Chalk Line Reel
Figure 2.5 Spirit level
Figure 2.4 Chalk line reel
Figure 2.4: This tool is very useful for marking straight
lines by holding the line taut between two extremes, lifting at any mid point with finger and thumb and flicking
onto the surface to leave a straight chalk line. The line is
retractable by winding a hinged handle housed in the
die-cast aluminium case, that folds back after use.
Powdered chalk is available in colours of red, white,
blue, orange, green and yellow. The reel has a subsidiary
use as a plumb bob – but it is not ideal for this purpose.
2.2.5 Spirit Level
Figure 2.5: This is an essential tool for plumbing and
levelling operations. Sizes vary between 200 mm and
2 m long, but a level of 800 mm length is recommended for general usage and easy accommodation in
the tool kit. A small level of 200 mm to 300 mm
length, called a boat level or torpedo level, is also recommended for use in restricted areas. Heavy-duty
levels of aluminium alloy die-cast, or lightweight
models of extruded aluminium, with clear, tough
plexiglass vials (containing spirit and trapped bubble),
epoxy-bonded into their housings to give lasting accuracy, are the most popular levels nowadays.
Even though these levels are shockproof, they
should not be treated roughly, as body damage can
affect accuracy. After use, avoid leaving levels lying on
the floor or ground to be trodden on, especially when
partly suspended, resting on other objects such as scrap
timber. When checking or setting up a level or plumb
position, be sure that the bubble is equally settled
between the lines on the vial for accurate readings.
2.2.6 Straightedges
Figure 2.6 Straightedge
Figure 2.6: In the absence of very long spirit levels,
straightedges may be used. These are parallel, straight
10
Tools Required: their Care and Proper Use
softwood boards of various lengths, for setting out or
(with a smaller spirit level held against one edge) for
plumbing and levelling. If transferring a datum point
in excess of the straightedge length, the risk of a
cumulative error is reduced by reversing the
∗
straightedge end-for-end at each move. Traditionally,
large holes were drilled along the centre axis to prevent
the board from being claimed for other building uses.
2.2.7 Plumb Bob
Figure 2.7: There is still a use, however limited, for
these traditional plumbing devices. The short one in
the illustration is made of steel, blacked to inhibit
rust; the other, which is a heavier type of 4 -12 ounces,
has a red plastic body filled with steel shot and a 3 m
length of nylon line. They should, as illustrated,
always be suspended away from the surface being
checked and measured for equal readings at top and
bottom. If in possession of a tarnishable steel plumb
bob, wipe with an oily rag occasionally. Although
commonly called plumb bobs, if they are pointed on
the underside, they are really centre bobs. The point is
very useful for plumbing to a mark on the floor.
2.2.8 Combination Mitre Square
∗
∗ Equal readings
Figure 2.7 Plumb bobs
Blade locking-nut
Inset spirit vial
Scribing pin
Figure 2.8 Combination mitre square
Figure 2.8: This tool was adopted from the engineering
trades and is now widely favoured on site work for the
following reasons: it is robust (the better, more expensive type) and withstands normal site abuse; it can be
used for testing or marking narrow rebated edges, as
shown, or for testing or marking angles of 90⬚, 45⬚, and
135⬚; the blade can be adjusted from the stock to a set
measurement and, with the aid of a pencil, used as a
pencil gauge. This facility is useful for marking sawn
boards, for example, as opposed to using a marking
gauge that may not be clearly visible on a rough sawn
surface. The square’s stock has an inset spirit vial and
can be used for plumbing and levelling – although this
is not the tool’s best feature. The blade locking-nut
Marking and Measuring
should always be tightened after each adjustment,
otherwise inaccuracies in the angle between the stock
and blade will readily occur, causing errors in marking
or testing. Finally, a scribing pin is usually located in the
end of the stock. This is a feature carried over from the
square’s originally intended use as an engineering tool
and is used for marking lines on metal.
2.2.9 Sliding Bevel
11
Figure 2.10: This tool, originally called a steel square or
steel roofing square, is now metricated and referred to as
a metric rafter square. Its size is 610 ⫻ 450 mm. The
long side is called the blade, the short side the tongue.
This traditional tool, primarily for developing roofing
bevels and lengths (covered in the chapter on roofing),
has a good subsidiary use as a try square, for marking
and testing certain right angles with greater opposite
sides than the combination square or normal try
square can deal with effectively.
2.2.11 Roofmaster Square
Figure 2.9 Sliding bevel
Figure 2.9: This is basically a slotted blued-and-hardened steel blade, sliding and rotating from a hardwood
(rosewood) or plastic stock. The plastic is impactresistant. The blade is tightened by a screw or a half
wing nut. The latter is best for ease and speed, being
manually operated. This is an essential tool for angular
work, especially roofing if using the Roofing Ready
Reckoner method. For protection against damage,
always return the blade to the stock-housing after use.
2.2.10 Steel Roofing Square/Metric
Rafter Square
Figure 2.11 The Roofmaster (Artistic representation only)
Figure 2.11: This revolutionary roofing square, as mentioned in the chapter on roofing, is well worth considering as an alternative to a traditional type roofing square.
It is a compact, precision instrument, measuring
335 mm on each right-angled side and is of anodized
Tongue
Blade
Figure 2.10 Steel roofing square
12
Tools Required: their Care and Proper Use
aluminium construction with easy-to-read laser-etched
markings. It gives angle cuts for all roof members and
the lengths of rafters without the need for separate
tables. It is designed for easy use, whereby only the roof
pitch angle is required to obtain all other angles and
lengths. (Readers wishing to obtain a Roofmaster
should contact Kingsview Optical Ltd., Harbour Road,
Rye, East Sussex, TN31 7TE, UK, Tel: ⫹44(0) 1797
226202, Fax: ⫹44(0) 1797 226301, Email:
[email protected] for further information.)
2.3 HANDSAWS
2.3.1 Introduction
Traditional handsaws, although still available at a relatively high cost, have been superseded by modern
hardpoint, throwaway saws. This is undoubtedly
because they are cheap to buy, have a higher degree of
sharpness, retain their sharpness for a much longer
period of time and, when blunt, can affordably be
replaced without the inconvenience – assuming a person has the skill – of re-sharpening. However, I have
included the following illustrations and references to
traditional saws, for those diehard traditionalists who
would still use them – and because the conventions
established with these saws (such as recommended
sawing-angles, etc) are still relevant.
2.3.2 Crosscut Saw
Figure 2.12: As the name implies, this is for cutting
timber across the grain. Blade lengths and points per
25 mm (pp25) or ppi (points per inch) vary, but
660 mm (26 in) length and 7 or 8 pp25 are recommended. All handsaw teeth on traditional type saws
contain 60⬚ angular shapes leaning, by varying
degrees, towards the toe of the saw. The angle of
lean, relative to the front cutting edge of the teeth,
is called the pitch. When sharpening saws, it helps to
know the required pitch. For crosscut saws the pitch
should be 80⬚. When crosscutting, the saw, as illustrated, should be at an approximate angle of 45⬚ to
the timber.
2.3.3 Panel Saw
Figure 2.13: This is a saw for fine crosscutting, which
is particularly useful for cutting sheet material such as
plywood or hardboard. A blade length of 560 mm
(22 in), 10 pp25 and 75⬚ pitch is recommended. When
cutting thin manufactured boards (plywood, hardboard, etc.), the saw should be used at a low angle of
about 15–25⬚.
7 pp25
Heel
Points per 25 mm
Toe of
saw
Pitch angle
45°
80°
60°
Tooth shape
Toe
Figure 2.12 Crosscut saw
10 pp25
Toe
75° 60°
15°
Figure 2.13 Panel saw
Handsaws
2.3.4 Tenon Saw
Figure 2.14 Tenon saw
Figure 2.14: This saw, because of its brass or steel back,
is sometimes referred to as a back saw. Technically
thought of as a general purpose bench saw for fine
cutting, it is however widely used on site for certain
second-fixing operations involving fine crosscutting of
small sections. The brass-back type, as well as keeping
the thin blade rigid, adds additional weight to the saw
for easy use. The two most popular blade lengths, professionally, are 300 mm (12 in) and 350 mm (14 in).
The 250 mm (10 in) saw is less efficient because of its
short stroke. On different makes of saw, the teeth size
varies between 13 and 15 pp25. For resharpening purposes, although dependent upon your skill and eyesight, 13 pp25 is recommended, with a pitch of 75⬚.
2.3.5 Rip Saw
Figure 2.15: This saw is used for cutting along or with
the grain and is not in great demand nowadays
because of the common use of machinery and portable
powered circular saws on site. However, it is not obsolete and can be very useful in the absence of power.
A blade length of 660 mm (26 in), 5 or 6 pp25 and a
pitch of 87⬚ is recommended. When ripping (cutting
along or with the grain), the saw should be used at a
steep angle of about 60–70⬚ to the timber. Because of
the square-edged teeth and pitch angle, this saw cannot be used for crosscutting.
Traditional saws should be kept dry if possible and
lightly oiled, but if rusting does occur, soak liberally
with oil and rub well with fine emery cloth.
2.3.6 Hardpoint Handsaws and
Tenon Saws
(a)
(b)
(c)
(d)
(e)
Figure 2.16 (a) Hardpoint handsaw; (b) hardpoint tenon
saw; (c) universal tooth-shape; (d) fleam tooth-shape;
(e) triple-ground tooth-shape
5 pp25
60°
Toe
87°
13
60°
Figure 2.15 Rip saw
14
Tools Required: their Care and Proper Use
Figures 2.16: These modern throwaway saws have highfrequency hardened tooth-points which stay sharper for
at least five times longer than conventional saw teeth.
Three shapes of tooth exist; the first, referred to as universal, conforms to the conventional 60⬚ tooth-shape
and 75⬚ pitch; the second, known as the fleam tooth,
resembles a flame in shape (hence its name), with a
conventional front-pitch of 75⬚, an unconventional
back-pitch of 80⬚, giving the fleam-tooth shape of 25⬚;
the third, referred to as triple ground, has razor-sharp,
circular-saw-type tooth geometry, enabling a cutting
action on both the push and the pull strokes. Most of
the handsaws are claimed to give a superior cutting
performance across and along the grain. Some saws in
the range have a Teflon-like, friction-reducing coating
on the blade, to eliminate binding and produce a
faster cut with less effort.
Range of Sizes
The saws usually have plastic handles – some with
improved grip – with a 45⬚ and 90⬚ facility for marking mitres or right angles. Handsaw sizes available are
610 mm (24 in) ⫻ 8 pp25, 560 mm (22 in) ⫻ 8 pp25,
508 mm (20 in) ⫻ 8 pp25, 560 mm (22 in) ⫻ 10 pp25,
508 mm (20 in) ⫻ 10 pp25, 480 mm (19 in) ⫻
10 pp25, 455 mm (18 in) ⫻ 10 pp25 and 405 mm
(16 in) ⫻ 10 pp25. Tenon saw sizes available are
300 mm (12 in) ⫻ 13 pp25, 250 mm (10 in) ⫻ 13
pp25, 300 mm (12 in) ⫻ 15 pp25 and finally 250 mm
(10 in) ⫻ 15 pp25. Three recommended saws from
this range would be the 610 mm (24 in) ⫻ 8 pp25 and
the 560 mm (22 in) ⫻ 10 pp25 black-coated handsaws
and a 300 mm (12 in) ⫻ 13 pp25 tenon saw.
2.3.7 Pullsaws
These lightweight, unconventional saws of oriental
origin, cut on the pull-stroke, which eliminates buckling. They can be used for ripping or crosscutting. The
unconventional precision-cut teeth, with three cutting
edges, are claimed to cut up to five times faster, leaving a smooth finish without breakout or splintering.
The sprung steel blade is ultra-hardened to give up to
ten times longer life and can easily be replaced at the
push of a button. Replacement blades cost about twothirds the cost of the complete saw, but a complete
saw is relatively inexpensive.
General Saw and Fine Saw
Figure 2.17: Only two saws from the range are illustrated here. The first is called a general carpentry saw
and has a 455 mm (18 in) blade ⫻ 8 pp25. This model
comes in two other sizes, 380 mm (15 in) ⫻ 10 pp25
and 300 mm (12 in) ⫻ 14 pp25. The latter is
(a)
(b)
Figure 2.17 (a) General carpentry saw; (b) fine cut saw
recommended for cutting worktops and laminates
without chipping. The second model is called a fine cut
saw and has a half-length back or full-length back
support and is said to surpass conventional tenon
saws. This model comes in two variations, one with a
fine-cut blade of 270 mm ⫻ 15 pp25, the other with
an ultra-fine blade of 270 mm ⫻ 17 pp25.
2.3.8 Coping Saw
Figure 2.18 Coping saw
Figure 2.18: This traditional tool has not changed or
lost its popularity and usefulness over many years. In
second-fixing carpentry, it is mainly used for scribing
(cutting the profile shape) of moulded skirting boards
where they meet in the corners of a room (covered in
another chapter), but occasionally comes in useful for
other curved cuts in wood or plastic. The saw blades
are very narrow with projecting pinned-ends and teeth
set at 14 pp25. The blades, although easily broken
with rough or unskilled sawing, have been heattreated to the required degree of hardness and toughness and are obtainable in packs of 10. Although the
narrowness of the blade demands that it be set in the
frame with the front pitch of the teeth set to face
the handle and working on the pull stroke, it can, if
preferred, be set to cut on the forward action, providing
that a degree of skill has been developed. The blade
can be swivelled to cut at any angle to the frame, after
unscrewing the handle slightly; the handle should be
fully tightened after each adjustment of the blade.
Hammers
2.3.9 Mitre Saw
15
Figure 2.20: Although this tool is basically for nailing
and extracting nails, it has also been widely used over
the years by using the side of the head as an alternative
to the wooden mallet. This is an acceptable practice
on impact-resistant plastic chisel handles – especially
as this type of handle is really too hard for the wooden
mallet – but it is bad practice to use a hammer on
wooden chisel handles, as they quickly deteriorate
under such treatment. However, in certain awkward
site situations, the mallet is too bulky and only the
side of the claw hammer is effective.
Other Uses
Figure 2.19 Mitre saw
Figure 2.19: Nowadays, portable electric mitre saws,
often referred to as ‘chop saws’ (because the rotating
saw is brought down onto the timber), have virtually
superseded wooden mitre boxes and mitre blocks and
offer a variety of other uses. These saws give speedy
and effortless precision-cutting and are widely used on
site and in small workshops. Although the main uses
cover cross cutting, bevel and mitre cutting, as well as
compound-mitre cutting, some models also have variable speed control (for low speed work on materials
such as fibreglass, etc) and a grooving stop for grooving and rebating work. There are a variety of makes
and different models available. The model drawn here
represents a DeWalt DEW 701 with ports for dust
extraction.
The claw is also used for a limited amount of leverage
work, such as separating nailed boards, etc. To preserve the surface shape of the head, the hammer
should not be used to chip or break concrete, brick or
mortar. When hammering normally, hold the lower
end of the shaft and develop a swinging wrist action –
avoid throttling the hammer (holding the neck of the
shaft, just below the head). Choice of weights is
between 450 g (1lb), 565 g (1-14 lb) and 675 g (1-12 lb);
choice of type is between steel shaft with nylon cushion grip, steel shaft with leather binding, fibreglass
shaft in moulded polycarbonate jacket and the conventional wooden shaft. The latter has a limited lifespan on site work. The choice is yours, but the
steel-shafted type with nylon cushion grip, 675 g in
weight, is recommended.
2.4.2 Mallet
Figure 2.21: The conventional wedge-shaped pattern,
made of beech, is rather bulky and not generally
favoured for site work, even though the tapered
2.4 HAMMERS
2.4.1 Claw Hammer
Figure 2.20 Metal-shafted claw hammer
Figure 2.21 Wedge-shape and round-head mallet
16
Tools Required: their Care and Proper Use
shaft – retaining the head from flying off – can be
removed for easier carriage. A recommended alternative is a round-headed mallet, such as a Tinman’s
mallet – used traditionally by sheet-metal workers –
which has a boxwood or lignum-vitae head of about
70 mm diameter. Finally, wooden mallets should only
strike on their end grain, not on their sides.
2.5 SCREWDRIVERS
Figure 2.22: Although power screwdrivers, especially
the cordless type, are very popular nowadays, hand
screwdrivers are still used and even preferred for certain jobs. Research has proved that the following
selection are still useful in the trade.
2.5.1 Ratchet Screwdriver
The ratchet screwdriver is available with flared slotted
tip in four blade-lengths of 75 mm, 100 mm, 150 mm
and 200 mm. They are also available with a No 2
Supadriv/Pozidriv tip and a No 2 Phillips’ tip in
blade-lengths of 100 mm only.
2.5.2 Spiral Pump Screwdriver
The spiral pump-action screwdriver, which can also be
used as a ratchet, comes in three sizes of 343 mm,
358 mm and 711 mm lengths when released by the
spiral lock. The spring release is fast and potentially
dangerous unless controlled by holding the knurled
sleeve at the front of the spiral shaft, next to the spiral
lock. This sleeve should also be held between
forefinger and thumb while pumping the screwdriver
with the other hand, in a screwing operation. The
358 mm size pump is recommended, but the 711 mm
size is very popular. A smaller version of the spiral
pump screwdriver is available, in one size of 267 mm
with a magazine handle holding two slotted bits, a
Pozidriv bit and two drill bits. The use of drill bits in
this compact-size pump is an attractive alternative for
making speedy pilot holes. Interchangeable bits are
supplied with the whole range of this type of screwdriver in different sizes of slotted and Pozidriv tips,
and can be purchased separately.
2.5.3 Plastic-Handled Screwdrivers
There is a large variety of these screwdrivers to
choose from, each with its own feature and qualities,
but some are not easy or comfortable to grip, often
making it difficult to apply the required torque. The
one illustrated in Figure 2.22(c) has a well-shaped
polypropylene handle integrated with thermo-plastic
elastomer inserts to provide improved grip and
comfort in use. The size of the tip varies according
to blade-length and these vary from 75 mm up
to 300 mm, with flared slotted tips, and from
75 mm up to 200 mm with Supadriv/Pozidriv or
Phillips’ tips.
2.6 MARKING GAUGES
Figure 2.23: These tools may not have a use on
first-fixing carpentry, but will be needed on secondfixing operations. Although still predominantly made
of beech, the thumbscrews are made of clear yellow
plastic and – although quite tough – if overtightened,
may fracture. To protect the sharp marking-pin and
for safety’s sake, the pin should always be returned
close to the stock after use. To use the gauge, it should
be held as shown, with the thumb behind the pin,
the forefinger resting on the rounded surface of the
stock and the remaining fingers at the back of the
stock, giving side pressure against the timber being
marked. Always mark lightly at first to overcome
grain deviations. The gauge is easier to hold if
the face-edge arris – that rubs the inside of the
outstretched thumb – is rounded off as shown.
Also, to reduce wear and surface friction, plastic
laminate can be shaped and bonded to the face of
the stock.
(a)
(b)
(c)
Figure 2.22 (a) Ratchet screwdriver;
(b) Spiral pump screwdriver; (c) Plastichandled screwdriver
Chisels
17
Thumbscrew
Stock
Stem
Rounded
arris
Figure 2.23 Marking gauge
Marking pin
2.7 CHISELS
as paring to a gauged line – where mallet/hammer
work, if any, is limited and levering should be avoided.
2.7.1 Firmer and Bevelled-edge
Chisels
2.7.2 Types of Chisels
(a)
(b)
Figure 2.24 (a) Firmer chisel; (b) Bevelled-edge chisel
Figure 2.24: Firmer chisels are generally for heavy
work, chopping and cutting timber in a variety
of operations where a certain amount of mallet/
hammer work and levering might be necessary to
remove the chopped surface. Bevelled-edge chisels
are generally for more accurate finishing tasks – such
Hollow-ground
25°
Although chisels with conventional wooden handles of
boxwood or ash are still available, they are more suitable
for bench joinery work, where they are less likely to
receive rough treatment. Because most site carpenters
will hit a chisel with the side of a claw hammer, the
modern range of chisels includes: splitproof handled
chisels with impact-resistant plastic handles, designed
for use with a hammer and guaranteed for life; black
non-slip polypropylene impact-resistant handled chisels; and heavy-duty shatterproof, cellulose acetate butyl
handled chisels. Blade widths range from 3 mm to
50 mm. Recommended sizes for a basic kit are 6, 10, 12
and 25 mm in firmer chisels (Figure 2.24(a)) and 18
and 32 mm in bevelled-edge chisels (Figure 2.24(b)).
2.7.3 Grinding and Sharpening Angles
Figure 2.25: The cutting edge of chisels should contain
a grinding angle of 25⬚, produced on a grindstone or
Flat-ground
30°
Figure 2.25 Grinding angle 25⬚;
sharpening angle 30⬚
18
Tools Required: their Care and Proper Use
grinding machine, and a sharpening angle of 30⬚, produced on an oilstone or a diamond whetstone. The
hollow-ground angle should not lessen the angle of
25⬚ in the concave of the hollow. For extra strength,
firmer and mortice chisels can be flat-ground.
Fine side of
oilstone
2.8 OILSTONES AND
DIAMOND WHETSTONES
Artificially manufactured stones, made from furnaceproduced materials, as opposed to natural stone, are
widely used because of their constant quality and relative cheapness. Coarse, medium and fine grades are
available. A combination stone, measuring 200 ⫻ 50 ⫻
25 mm, is recommended for site work. This stone is
coarse for half its thickness, and fine on the alternate
side for the remaining half thickness. As these stones
are very brittle, they should be housed in purpose-made
(or shop-purchased) wooden boxes for protection.
(a)
2.8.1 Oiling the Stone
When sharpening, use a thin grade of oil, animal or
mineral, but not vegetable oil, which tends to solidify
on drying, so clogging the cut of the stone.
Lubricating oil is very good. Should the stone ever
become clogged, giving a glazed appearance and a
slippery surface, soak it in petrol or paraffin for several
hours, then clean it with a stiff brush or sacking material and allow it to dry before re-using.
2.8.2 Sharpening
Figure 2.26: When sharpening chisels or plane irons,
first apply enough oil to the stone to cover its surface
and help float off the tiny discarded particles of metal,
then hold the tool comfortably with both hands,
assume the correct angle to the stone (30⬚), then move
back and forth in an even, unaltering movement until
a small sharpened (or honed) edge is obtained. This
action produces a metal burr which is turned back by
reversing the cutter to lay flat on the stone, under
finger-pressure, and by rubbing up and down a few
times. Any remaining burr can be removed by drawing
the cutter across the arris edge of a piece of wood.
2.8.3 Use of Oilstone
The stone should always be used to its maximum
length, the cutter lifted occasionally to bring the oil
back into circulation. Narrow cutters, such as small
chisels, whilst traversing the length of the stone, should
also be worked across the stone laterally to reduce the
risk of dishing (hollowing) the stone in its width.
(b)
Figure 2.26 (a) Recommended hand-hold for sharpening
a plane iron; (b) Removing metal burr and polishing
underside of cutting edge
2.8.4 Oilstone Box
Figure 2.27 Oilstone box
Figure 2.27: Although now available in tool shops,
this was traditionally a hand-made item, usually of
hardwood, required to protect the stone from damage
and the user from contact with the soiled oil. It is
easily made from two pieces of wood, each measuring
Hand Planes
19
Colour coding
a minimum of 240 ⫻ 62 ⫻ 18 mm, to form the two
halves of the box. With the aid of a brace and bit and
chisel (or a router, if available), recesses are cut to
accommodate the stone snugly in the base and loosely
in the part which is to be the lid. To stop the box from
sliding while sharpening, two 12 mm ⫻ 4 gauge screws
can be partly screwed into the underside of the base and
filed off to leave dulled points of about 2 mm projection.
The DMT® range of ‘stones’ have colour-coded bases,
denoting the grit or micron size of the diamonds.
Green ⫽ extra fine, 1200 grit, 9 micron; Red ⫽ fine,
600 grit, 25 micron (said to be the most popular for all
woodworking tools, including router and auger bits;
Blue ⫽ course, 325 grit, 45 micron (for general carpentry tools, including masonry drills); Black ⫽ extra
course, 220 grit, 60 micron (for damaged tools,
including cold chisels).
2.8.5 Diamond Whetstones
Technical details
The silver surface of the ‘stones’ is a layer of graded
mono-crystalline diamonds set two-thirds into nickel,
which bonds them to a perforated precision-ground
steel base. The base has been injection moulded onto a
polycarbonate/glass fibre substrate. This is of steel-like
rigidity and strength. Therefore, the whetstones will
stay flat and not bend, dish or groove throughout their
working life.
2.9 HAND PLANES
Figure 2.28 Diamond Whetstone
The two planes to be recommended as most useful
for site work are the No. 4 -12 smoothing plane with a
cutter width of 60 mm and a base length of 260 mm
and the No. 5 -12 jack plane, also with a cutter width
of 60 mm, but a base length of 381 mm. Narrower
smoothing and jack planes with 50 mm cutter widths
and less length and weight, notably the No. 4 and
the No. 5, are thought to be more suitable for bench
joinery work.
Figure 2.28: These modern sharpening surfaces are
now popular with many carpenters as an alternative to
traditional oilstones. This is because diamond whetstones allow fast and clean removal of the chisel or
plane iron’s blunt or damaged cutting edges, saving
time and reducing or eliminating the need to regrind.
They also give an unimpaired, lasting performance
under normal working conditions. To help float off
the micron-sized, discarded particles of metal,
Diamond Abrasive Lapping Fluid should be used
instead of oil. Although water can be used instead,
this can cause tool-rust. Hardwood boxes or plastic
cases are available for the range listed below. Non-slip
mats or bench holders can also be used as an alternative.
2.9.1 Knowledge of Parts
Figure 2.29 shows a vertical section through a
smoothing plane to identify the various parts which
need to be named and known for reference to the
J
I
E
H
N
P B
C
F
K
G
M
D
R
A
O
L
Q
S
Figure 2.29 Vertical section through smoothing
plane. The parts are: A mouth, B back iron, C frogfixing screws, D frog, E lever, F lever cap, G levercap screw, H back-iron screw, I cutting iron (cutter),
J lateral-adjustment lever, K cutter-projection
adjustment lever, L knurled adjusting-nut, M mouthadjustment screw, N knob, O handle, P
escapement, Q sole (base), R toe and S heel
20
Tools Required: their Care and Proper Use
2.10 RATCHET BRACE
plane’s usage. These named-parts also apply to the
jack plane and other planes of this type.
Figure 2.30: This item should be carefully chosen for
its basic qualities and any saving in cost could prove to
be foolish economy. Essentially, the revolving parts –
the head and the handle – should be free-running on
ball bearings, the ratchet must be reliably operational
for both directions and the jaws must hold the
tapered-tang twist bits, and the dual-purpose combination auger bits with parallel shanks, firmly and concentrically. The recommended sweep (diameter of the
handle’s orbit) is 250 mm. Braces with a smaller or
larger sweep are available. The advantages of the
ratchet are gained when drilling in situations where a
full sweep cannot be achieved, such as against a wall
or in a corner – or when using the screwdriver bit
under intense pressure and sustaining the intensity by
using short, restricted ratchet-sweeps.
2.9.2 Planing and Setting-up
Details
These planes are also available with corrugated
(fluted) bases to reduce surface friction, especially
when planing resinous or sticky timbers; if not fluted,
the sole of the plane can be lightly rubbed with a piece
of beeswax or candlewax. When planing long lengths
of timber, like the edge of a door, lift the heel slightly
at the end of the planing stroke to break the shaving.
On new planes, the cutter has been correctly ground
to 25⬚, but not sharpened. To sharpen, remove the
cutter from the back iron and carry out the sharpening
procedure outlined in the text to Figure 2.26. When
re-assembling, set the back iron within 1–2 mm of the
cutter’s edge and, if necessary, adjust the lever-cap
screw so that the replaced lever cap is neither too tight
nor too loose.
2.11 BITS AND DRILLS
2.9.3 How to Check Cutterprojection
2.11.1 Twist Bits and Flat Bits
Figure 2.31: Twist bits are also referred to as auger bits
and traditional types are spiral-fluted, round shanked
with tapered tangs. Their disadvantage nowadays is
that they will only fit the hand brace and not the electric or cordless drill. However, a set of modern bits,
without this disadvantage, is now an option. These
bits are also spiral-fluted and round shanked, but are
minus the tapered tang and will fit either the
electric/cordless drill or the ratchet brace. They are
known as combination auger bits. All of these bits are
for drilling shallow or deep (maximum 150 mm) holes
of 6–32 mm diameter. Jennings pattern twist bits have
a double spiral and are used for fine work; Irwin
Always check the cutter projection before use,
by turning the plane over at eye-level and sighting
along the sole from toe to heel. The projecting cutter
will appear as an even or uneven black line. While
sighting, make any necessary adjustments by moving
the knurled adjusting-nut and/or the lateral-adjustment lever. For safety and edge-protection, always
wind the cutter back after final use of the plane.
Bear in mind that the body is made of cast iron, and
if dropped, is likely to fracture – usually across the
mouth. Keep planes dry and rub occasionally with
an oily rag.
B
half
swing
D
CL
A
G
E
F
C
G
Figure 2.30 Ratchet brace.
Parts of the brace are named as
follows: A head, B handle, C
ratchet, D ratchet-conversion
ring, E jaws-adjustment shell, F
universal jaws, and G oil hole
Bits and Drills
Jennings pattern twist bit
21
locations. For example, when drilling through the
sides of in situ floor/ceiling joists in a rewiring job.
Sizes of flat bits range from 6 mm to 40 mm.
2.11.2 Drilling Procedure
Irwin solid-centre twist bit
Sandvik combination auger bit
If the appearance of a hole has to be considered, then
care must be taken not to break through on the other
side of the timber being drilled. This is usually
achieved by changing to the opposite side immediately the point of the bit appears. Alternatively, drill
through into a piece of waste timber clamped onto or
seated under the blind side.
2.11.3 Sharpening Twist Bits
Bahco flat bit
Figure 2.31 Twist bits/auger bits and flat bits
solid-centre twist bits have a single spiral and are
more suitable for general work; Sandvik combination
auger bits have a wide single spiral with sharp edges
and give a clean-cut hole suitable for fine or general
work. Seven combination bits are recommended
for the basic kit, these being sizes 6, 10, 13, 16, 19, 25
and 32 mm.
Flat bits are ideal for use with electric or cordless
drills and are now produced by some manufacturers
with non-slip hexagonal shanks (not available on
6 mm diameter), suitable for SDS (Special Direct
System) chuck systems, allowing quick release.
Another improvement in recent years is the winged
shoulders, enabling the bit to score the perimeter of
the hole before cutting the material. Because of their
flat, simple design, which reduces side friction, they
cut a lot faster and with less effort than twist or auger
bits; but this simple design feature can be a disadvantage when drilling holes that need to be more precise,
at right angles to the surface of the material – and
where the bore hole does not wander within the
material. However, this tendency (or capability) of
wandering when below the surface, can be put to
advantage when drilling certain holes in awkward
Always avoid sharpening twist bits for as long as
possible, but when you do, sharpen the inside edges
only, with a small flat file; never file the outer surface
of the spur cutters. Always take care, when drilling
reclaimed or fixed timbers, not to clash with concealed
nails or screws, as this kind of damage usually ruins
the twist bit.
2.11.4 Countersink Bits
Figure 2.32: These are for screw-head recessing in soft
metal and timber. The rosehead pattern type is for
metals, such as brass or aluminium, although it is also
used for softwood (and can be used for hardwood).
The snailhorn pattern type is used just for hardwood.
As illustrated, these are available with a round shank
and traditional tapered tang for use with the ratchet
brace, or with short or long, round shank only, for use
with the hand drill or the electric or cordless drill.
2.11.5 Combined Countersink and
Counterbore Bits
Figure 2.33: These two modern drill-bits are useful on
certain jobs and although they can be used in traditional hand drills, they will of course be more efficient
in electric or cordless drills. The combined countersink bit is available in seven different sizes and is for
drilling a pilot hole, shank hole and countersink
for woodscrews in one operation. The combined
Figure 2.32 (a) Rosehead and (b) snailhorn
countersink bits
22
Tools Required: their Care and Proper Use
Figure 2.33 (a) Combined countersink, shank
and pilot bit; (b) combined counterbore, shank
and pilot bit
(a) Double-ended bit
(b) Single-ended hex bit
(c) Single-ended bit
(d) Double-ended bit
counterbore bit is available in 12 different sizes and is
for drilling a pilot hole, shank hole and a counterbored hole (the latter receives a glued wooden pellet
after screwing) also in one operation.
2.11.6 Screwdriver Bits
Figure 2.34: There is a wide range of modern bits
suitable for electric or cordless drills, in different
lengths (Figures 2.34(a) and (b)) to fit different
gauges of screws and different types, such as screws
with Supadriv/Pozidriv inserts, Phillips’ inserts and
slotted inserts. The two traditional screwdriver bits
shown in Figures 2.34(c) and (d) have tapered
tangs for use with the ratchet brace. These bits
are still very useful, mainly for the extra pressure and
leverage obtained by the brace and occasionally
required in withdrawing or inserting obstinate or
long screws. The double-ended bit (d) has a different
size slotted tip at each end, in the shape of – and to
act as – a tang.
2.11.7 Twist Drills and Masonry
Drills
Figure 2.34 Screwdriver bits
Figure 2.35: The twist drill is another of those
tools adopted from the engineering trades and
put to good use in drilling holes in timber. Their
round shanks will fit the chuck of the electric,
cordless, or hand drill. A set of these twist drills, of
high-speed steel (HSS), varying in diameter by
0.5 mm and ranging from 1 mm to 6 mm, is essential
for drilling pilot holes and/or shank holes for screws
in timber. They may also be used of course for drilling
holes in metals such as brass, aluminium, mild steel,
etc. (after marking the metal with a centre punch).
When dull, these drills can be sharpened on a grinding wheel, but care must be taken in retaining the
cutting and clearance angles at approximately 60⬚ and
15⬚, respectively.
Masonry drill-bits of various diameter for drilling
plug holes in brick, block and medium-density concrete, or similar materials, have improved in recent
years and are now available with high quality, heavy
duty carbide tips.
2.11.8 SDS Drills
Figure 2.36 SDS-Plus drill bit
59°
HSS twist drill (100 ⫻ 6 mm)
Masonry drill
59°
59°
Figure 2.35 Twist drills and masonry drills
15°
cutting and
15° clearance
angles
Figure 2.36: These high performance drill-bits, manufactured from high grade alloy tool steel, mainly for
drilling into dense concrete, or similar material, are for
use with the powerful SDS-Plus and SDS-Max range
of hammer drills and pneumatic hammer drills with
SDS (Special Direct System) chucks. The drill-bits
have standardized shanks that slot into the special
chuck arrangements with automatic locking devices
and quick release.
Individual Handtools
23
2.12 INDIVIDUAL HANDTOOLS
2.12.1 Bradawls
Figure 2.39 Wrecking bar
Figure 2.37 Bradawls
Figure 2.37: These are used mainly for making small
pilot or shank holes when starting screw fixings. Two
different sizes are available and different types. One
type of awl has a flat brad-head point which should
always be pushed into the timber at right angles to the
grain before turning; the other type of awl has a squaresectioned, tapered point which acts as a reamer when
turned – ratchet fashion – into the timber. Although it
seems to be less common, the square-tapered awl
(called a ‘birdcage awl’) is very much recommended.
in construction work for extracting large nails and for
general leverage work. There is a choice of five sizes:
300, 450, 600, 750 and 900 mm. If necessary, leverage
can be improved by placing various-size blocks
under the fulcrum point. The 600 mm length is
recommended.
2.12.4 Hacksaw
Figure 2.40 Junior hacksaw
2.12.2 Pincers
Figure 2.40: This is another useful addition occasionally required. Carpenters do not normally need a fullsize hacksaw for cutting large amounts of metal
objects, so the junior hacksaw, with a blade length of
150 mm, is recommended for the limited amount of
use involved.
Figure 2.38 Pincers
Figure 2.38: These are used for withdrawing small
nails and pins, not fully driven in. Although these are
usually extracted by the claw hammer, occasionally a
pair of pincers will do the job more successfully. When
levering on finished surfaces, a small piece of wood or
thin, flat metal placed under the fulcrum point will
reduce the risk of bruising the surface. Different sizes
are available, but the 175 mm length is recommended.
2.12.3 Wrecking bar
Figure 2.39: This tool is also referred to as a crowbar,
nail bar or pinch bar. It is not essential, but is useful
2.12.5 Nail Punches
Figure 2.41 Nail punches
Figure 2.41: These are essential tools, especially in
second-fixing carpentry, when used to sink the heads
of nails or pins below the surface of the timber, by
about 2 mm, to improve the finish when the hole is
stopped (filled) prior to painting. They are also of use
24
Tools Required: their Care and Proper Use
occasionally, assisting in driving a nail into an awkward position, or in skew-nailing into finished timbers, switching to a punch to avoid bruising the
surface with the hammer. At least three nail punches
are recommended for the basic kit, say 1.5, 2.5 and
5 mm across the points. Some points have a concave
shape to reduce the tendency to slip.
D VOLTAGE
METAL AND
VOLTAGE
DETECTOR
METAL AN
Safety Note
Figures 2.41 and 2.42: For safety’s sake, grind the sides
of the heads before they become too mushroomshaped from prolonged usage. Also, develop the technique of holding the tool as you would the barrel of a
rifle, so that the palm of the hand, not the knuckles,
faces the hammer blows. Alternatively, plastic grip
hand guards are available separately to fit onto chisels.
2.12.7 Electronic Detectors
Figure 2.43: These electronic instruments are very useful for detecting the location of any surface-concealed
electric cables, gas and/or water pipes. This preliminary detection is essential on plastered or dry-lined
ceilings and walls and screeded or boarded floors,
where blind fixings or drilling for fixings may cause a
costly and/or messy disaster. There are a variety of
these instruments available, although some only detect
power and pipes. Others detect stud or joist positions,
DETECT
DETECT
2.12.6 Cold Chisel and Bolster Chisel
Figure 2.42: A 19 ⫻ 300 mm cold chisel and a bolster
chisel with a 75 mm wide blade are recommended
additions to the tool kit, for use on odd occasions
when brick or plasterwork requires cutting. Carbon
steel chisels are commonly used, although nickel alloy
chisels are more suitable. Keep the cutting edges
sharp, by file for nickel alloy and by grinding wheel for
carbon steel.
R
DETECTO
Figure 2.43 Electronic Detector
with an LED display and buzzer indicator. A few
detect all three elements. The model drawn here
represents a West WST165 Metal and AC Voltage
Detector. This particular model also indicates if
cables, power points, junction boxes, etc, are live.
2.13 PORTABLE POWERED AND
CORDLESS CIRCULAR SAWS
Figure 2.44(a): These saws are widely used nowadays
to save time and energy spent on handsawing operations. Although basically for ripping and crosscutting, they can also be used for bevel cuts, sawn
grooves and rebates. Models with saw blades of about
240 mm or more diameter are recommended for site
work.
Figure 2.44(b): Cordless circular saws are now available for site and general use, but because of the
limited power supply from rechargeable batteries, may
not be constantly powerful enough for heavy ripping
work. However, they can be very useful on sites without any electricity supply. The saw recommended and
illustrated here is the DeWalt 007K, 24 volt heavy
duty model with a 165 mm diameter blade, which
gives a 55 mm depth of cut.
Cold chisel (19 ⫻ 300 mm)
Dangerous
mushroomed-head
Bolster chisel (75 mm)
45°
45°
Recommended grinding angles
Figure 2.42 Cold chisel and bolster
chisel
Powered and Cordless Drills and Screwdrivers
Crosscutting
Ripping
Trigger control
Motor
Front
handle
Base
plate
Top
guard
Quadrant arm
Saw
blade
Telescopic
saw guard
Sawn groove
Before starting to cut, the saw should be allowed to
reach maximum speed and should not be stopped or
restarted in the cut. Timber being cut should be
securely held, clamped or fixed – making certain that
any fixings will not coincide with the sawcut and that
there are no metal obstacles beneath the cut. Always
use both hands on the handles provided on the saw, so
reducing the risk of the free hand making contact with
the cutting edge of the blade. At the finish of the cut,
keep the saw suspended away from the body until the
blade stops revolving.
2.13.3 Safety Note
Detachable/
adjustable
fence
Bevel cut
end of the timber being cut, it will automatically
spring back to give cover again when the cut is complete. For ripping, a detachable fence is supplied.
2.13.2 Using the Saw
Rear handle
Power
cable
25
Rebate
(a)
Additional safety factors include: keeping the power
cable clear of the cutting action; not overloading the
saw by forcing into the material; drawing the saw back
if the saw-cut wanders from the line and carefully readvancing to regain the line; wearing safety glasses or
protective goggles; disconnecting the machine from
the supply while making adjustments, or when it is
not in use; keeping saw blades sharp and machines
checked on a regular basis by a qualified electrical
engineer; checking voltage and visual condition of
saw, power cable and plug before use; and working in
safe, dry conditions.
2.14 POWERED AND
CORDLESS DRILLS AND
SCREWDRIVERS
(b)
Figure 2.44 (a) Portable powered circular saw;
(b) cordless circular saw
2.13.1 Adjusting the Base Plate
Before use, the saw should be adjusted so that when
cutting normally, the blade will only just break
through the underside of the timber. This is easily
achieved by releasing a locking device which controls
the movement of the base plate in relation to the
amount of blade exposed. For bevel cutting, the base
tilts laterally through 45⬚ on a lockable quadrant arm.
The telescopic saw guard, covering the exposed blade,
is under tension so that after being pushed back by the
Figure 2.45: There is nowadays a wide range of dualand triple-purpose drills to choose from, starting with
the basic rotary-only drill and ending with the
advanced electro pneumatic hammer drill. In the
electric-powered range, of either 110 or 240 volts, the
following combinations are available: the drill/screwdriver, drill/impact (percussion) drill/screwdriver,
drill/rotary hammer drill/screwdriver, and combinations
of battery-powered models such as the cordless screwdriver, drill/screwdriver, drill/impact drill/screwdriver,
and the drill/rotary hammer drill/screwdriver. Careful
consideration needs to be given in choosing a particular model in relation to the type of work to be done
and its location regarding whether power is readily
available and if so, whether it is 110 or 240 volts.
26
Tools Required: their Care and Proper Use
C
●
A
D
B
E
(a)
A
B
C
D
E
Depth gauge
Keyless chuck
Speed control
Trigger
Removable handle
●
●
●
●
12 v
(b)
●
Figure 2.45 (a) Powered drill; (b) cordless
drill/screwdriver
2.14.1 Technical Features of Drills
and Drivers
●
●
●
●
Drills with rotary impact or percussion action create a
form of hammer action generated by a ridged
washer-type friction bearing and should only be used
for occasional drilling into masonry or concrete.
Drills with rotary hammer action are designed with
an impressive impact mechanism involving a reciprocating piston and connecting rod, which strikes
the revolving drill bit at between 0 and 4000 blows
per minute on certain models. This makes drilling
of masonry or concrete much easier and faster and
is recommended when drilling into these materials
frequently.
Drills with electro pneumatic rotary hammer action
are designed with an impact mechanism which
converts the power into a reciprocating pneumatic
force to drive a piston and striker at between 0
and 4900 blows per minute on certain models. It
develops eight times the power of a normal hammer drill and is recommended for ease, speed and
efficiency when drilling frequently or constantly
into masonry or concrete.
Safety clutches are torque-limiting mechanisms
fitted to impact and hammer drills to protect
the user if the drill bit becomes jammed in the
material being drilled. They also protect the gears
of the machine and the motor from short-term
overloading.
Chucks either have three jaws and require a separate
chuck key, or are hand-operated and known as
keyless chucks. Chuck sizes are usually 10, 13 and
16 mm. Some combination drills have an SDS
chuck system, using special quick-release keyless
chucks that accept only SDS drill bits.
The Fixtec system on some SDS drills enables an
SDS chuck to be replaced quickly by a standard
three-jaw chuck without the use of tools.
Hex in spindle means that a drill with this facility
has a 6.35 mm ( -14 in) hexagon recess in the drive
spindle (accessible after removing the chuck) to
take hexagon shanked screwdriver bits.
Drills with variable electronic speed have an accelerator function for gentle start-up during drilling and
screwdriving and, on certain jobs, can be used for
driving in screws without first drilling a pilot hole.
Drills with adjustable torque control can be preset
and gradually adjusted to achieve precise screwdriving tightness.
Reversing rotation is available with some drills and
drivers, which is necessary for removing screws –
and desirable when bits get jammed in a drilling
operation.
2.14.2 Safety Note
Small pieces of loose timber being drilled should be
firmly held or clamped; reliable step ladders,
trestles, orthodox platforms or scaffolds should be
used when drilling at any height above ground level;
safety glasses or protective goggles should be worn;
before making adjustments, or when not in use, a
machine should be disconnected from the power supply; bits should be resharpened or renewed periodically; machines should be maintained on a regular
basis by a qualified electrical engineer or by the manufacturer; always check visual condition of machine,
power cable and plug or socket before use; always keep
a proper hold on the drill until it stops revolving;
always work in safe, dry conditions. On certain jobs,
wear hard hats/helmets.
2.15 POWERED AND
CORDLESS PLANERS
Figure 2.46: Powered planers are often used nowadays
in conjunction with traditional planes such as the jack
and the smoothing plane. They are sometimes preferred on such jobs as door-hanging, to lessen the
strenuous task of ‘shooting-in’ the door by planing
its edges. However, on this particular job, it is good
Powered and Cordless Jigsaws
Figure 2.46 Powered planer
practice to finish off with a hand plane, to remove the
unsightly rotary-cutter marks – which can be very
pronounced if the planer is pushed along at too great a
feed-speed.
27
three by this particular manufacturer. It has a TCT
(tungsten carbide tip) cutter with a width of 82 mm,
planing depth of 0–3 mm, rebating depth of 0–22 mm,
vee grooves in the base to facilitate chamfering, a
safety switch catch to prevent unintended starting and
an automatic pivoting guard enclosing the cutter block
for increased safety. This latter feature allows the
planer to be put down safely before the revolving cutter block has come to a stop. One of the other models
of this industrial threesome has an increased cutter
width of 102 mm, but a reduced planing depth of
0–2.5 mm. Both models mentioned run at a no-loadspeed of 13 000 rpm.
2.16 POWERED AND
CORDLESS JIGSAWS
Figure 2.48: Whether mains-powered or batteryoperated (cordless), the essential purpose for a jigsaw
is to enable pierced work to be carried out. This
self-explanatory term means to enter the body of a
material, without leading in from an outside edge. By
so doing, small, irregular shapes can be cut. Nowadays,
Figure 2.47 Cordless planer
Figure 2.47: Cordless planers are now available for site
and general use, but because of the limited power supply from rechargeable batteries (although two are supplied with a charger) and the limited cutting depth of
0.5 mm, they do not have as much industrial appeal as
a mains-powered planer. However, with both batteries
fully charged, they can be useful for a period of time
on sites without any electricity supply. The cordless
planer illustrated here is the Makita 1051DWDE
14.4 volt model. It has a no-load-speed of 9000 rpm,
maximum planning/cutting depth of 0.5 mm, rebating
depth of 15 mm, a planing width of 50 mm and
weighs 2.1 kg.
(a)
2.15.1 Making the Choice
When choosing a planer for frequent or constant use,
avoid models classified in a DIY range; choose one
with a professional/industrial classification. The
model illustrated in Figure 2.46 is one in a range of
(b)
Figure 2.48 (a) Powered jigsaw; (b) Cordless jigsaw
28
Tools Required: their Care and Proper Use
with different blades, this can be done in wood,
certain metals and ceramic tiles. Although the initial
entry into wood can be done by the saw itself, by resting the saw’s front base and tip of the saw on the surface and pivoting the moving saw blade gradually
through the material’s thickness, the usual way is to
drill a small hole to receive the narrow blade. A typical
carpentry use for a jigsaw is in fitting a letter plate,
described and illustrated here in the chapter on fitting
locks, latches and door furniture. The secondary purpose for jigsaws is in cutting curved and irregular
shapes by leading in from an outer edge. The powered
jigsaw represented here is a DeWalt model DEW
331K, with a 701 watt power input, 130 mm depth of
cut in wood, variable speed, keyless blade change,
adjustable orbital action and dust extraction adaptor.
The cordless jigsaw represented here is a DeWalt
model DEW DC330KA 18 volt with two rechargeable batteries, an impressive 130 mm depth of cut in
wood, variable speed, 3 pendulum cutting actions, a
blower and dust extraction hub.
(a)
(b)
Figure 2.49 (a) Powered SDS rotary hammer drill;
(b) cordless SDS rotary hammer drill
2.17 POWERED AND
CORDLESS SDS ROTARY
HAMMER DRILLS
Figure 2.49: Powered and cordless SDS (Special
Direct System) electro pneumatic rotary hammer
drills, using special SDS masonry drills for high performance and durability, are essential nowadays for
drilling into dense concrete, stone and masonry. Some
models come with a rotation-stop facility to enable
SDS tools to be used for chiselling operations. The
electro pneumatic rotary hammer action has an
impact mechanism which converts the power into a
reciprocating pneumatic (compressed air) force to
drive a piston and striker up to 4900 blows per minute
on certain models. It is claimed to develop eight times
the power of a normal hammer drill. There are two
types of SDS chuck available for SDS bits. One is the
SDS-Plus chuck and the other is the SDS-Max
chuck. The SDS-Max is for heavy drilling and core
cutting in concrete, and chiselling operations. Bitshank profiles differ, so an SDS-Plus bit must only be
used in an SDS-Plus chuck and, likewise, an SDSMax bit must only be used in an SDS-Max chuck –
although separate adaptors are available. The powered
rotary hammer drill represented here is a 900 watt
DeWalt DEW D25404K heavy-duty SDS-Plus combination hammer drill, capable of drilling 32 mm
diameter holes in concrete. The cordless model represented here is an 18 volt DeWalt DEW 999K2 heavyduty SDS-Plus rotary hammer drill.
2.18 POWERED (PORTABLE)
ROUTERS
6
5
4
3
2
1
Figure 2.50 Powered router
Jigs
(a)
0×
60
mm
20
0×
60
mm
21
m
0m
22
0
×5
Figure 2.50: Nowadays, portable powered-routers are
often used on site for simplifying and speeding up certain second-fixing jobs. These include cutting recessed
housings for door hinges; apertures for letter plates
(often referred to as letter boxes); mortises for door
locks and latches; joints in laminate kitchen-worktops
with postformed edges; end-shaping of laminate
worktops; cutting ‘dog-bone’ or ‘T-shaped’ recesses for
inserting panel bolt connectors (these act like traditional handrail bolts in pulling up and holding worktop joints together); and cutting segmental slots in the
joint-edges of worktops for the insertion of so-called
‘biscuits’. These elliptical-shaped biscuits are manufactured in different sizes (size 20 is required to suit
the biscuit-jointing cutter used in routers) and are
pressed and cut to shape from ‘feather-grained’ beech
(a traditional term meaning that the grain is at 45⬚
across the face of the timber). This is done to eliminate the risk of the thin biscuits splitting along the
grain when positioned within the joint. Although the
insertion of three or four biscuits per worktop joint
improves the joint’s stability, their main function is to
ensure surface flushness of the two joined worktops.
To perform the heavier tasks mentioned above, you
will need a plunge router with a power input of at
least 1300 watts. The router illustrated here represents
a DeWalt DEW629 plunge router with a -12⬙
(12.7 mm) collet, essential for receiving the -12⬙
shank router cutters required for the heavier cutting.
It has a 1300 watt power input, a no-load-speed of
22000 revs per minute and a plunge-movement
depth of 62 mm.
29
(b)
(c)
(d)
2.19 JIGS
Figure 2.51(a)(b)(c)(d): All of the above operations,
except biscuit jointing, are performed with the aid
of special patented jigs which are clamped or attached
to the work surface. The hinge jig represented at
(a) is the H/JIG/75 by Trend, for routing 75 mm
hinge recesses in internal doors and linings. Made
of hard wearing, 12 mm laminate in two lengths
for easy handling, it is joined together by a dovetail
joint. No marking out of door or lining is needed.
It has traditional settings for three hinges, 150 mm
down, 225 mm up and middle – middle being
optional, of course. There is a swivel end plate to
give the 3 mm joint (gap) at the door-head. The jig
is positioned by inserting three 10 mm Ø plastic
pins (supplied) along its length, to locate against
the edges of the door and lining. Then the jig is
secured to the work surface for routing by inserting
two bradawls (also supplied) through small holes
in its face.
Figure 2.51 (a) Two-part hinge jig; (b) letter plate jig;
(c) lock jig; (d) kitchen-worktop jig
The letter plate template (jig) illustrated at (b) is
the Trend TEMP/LB/A, made from 8 mm clear plastic, for cutting three sizes of aperture to suit letter
plates 220 ⫻ 50 mm, 210 ⫻ 60 mm and 200 ⫻ 60 mm
on doors up to 50 mm thick. The template/jig is
secured in its cutting position by small countersunk
screws, strategically placed in the two centres required
for letter-plate bolts. A -12⬙ (12.7 mm) collet, plunge
router is required.
The lock jig illustrated at (c) is the Trend LOCK/
JIG, which uses a set of separate, interchangeable
templates to suit the mortise and face-plate recesses
of popular sized door locks. The templates are held
in position by two powerful magnets. The jig is
fixed to the door, as indicated, by its own clamping
devices.
30
Tools Required: their Care and Proper Use
Finally, the kitchen-worktop jig represented at (d)
is a Trend COMBI 651 jig, made from 16 mm thick,
hard wearing solid laminate. The holes that receive
location-bushes for the different functions are colourcoded for quick and easy use and three alloy bushes
are supplied with a width-setting stop. Worktops from
420 mm to 650 mm width can be jointed. There are
two template-apertures for cutting T-shaped recesses
for the panel bolt connectors and a radius edge for
forming peninsular end-cuts.
(a)
2.20 NAILING GUNS
2.20.1 Nailing Guns for Wood to Wood
Fixings
Figure 2.52(a)(b)(c): Although carpenters’ claw hammers are still basically essential tools, nail guns are
being used additionally on sites nowadays – especially
on new-build projects. The reason for this is that these
tools eliminate the effort involved in repetitive nailing
and speed up the job. The three main types of nail gun
to choose from are:
●
●
●
(a) Pneumatic nail guns, involving air hoses and a
portable compressor. The advantages with these
tools include a capability of nail-size up to 100 mm
(4⬙) and lower maintenance and running costs. The
obvious disadvantage is the handicap of working
with and around air hoses and a compressor –
although portable, 10-bar compressors are available
in quite small units, weighing from 16 to 25 kg, and
hoses up to 30 m long.
(b) Cordless nail guns using gas fuel cells, a spark
plug and a rechargeable battery. A triggered spark
ignites fuel in a combustion chamber, forcing a piston to drive the loaded-nail to a pre-set depth. The
main advantage with these tools is the fact that
they are without restriction by virtue of being
cordless. The disadvantages are that their capability
of nail-size is limited to 90 mm (3 -12⬙) and they
require higher maintenance and running costs.
(c) Cordless nail guns operated by rechargeable
batteries only. The weight of this tool is about
1.5 kg heavier than its equivalent in group (b) and
about 2.4 kg heavier than its equivalent in group
(a), otherwise it has the same advantage as group
(b) of being cordless and unrestricted. It does not
use gas fuel cells, so running costs will be lower
and there should be less maintenance involved.
However, nail-size capability is limited to
63 mm (2 -12⬙).
The (a) and the (b) types mentioned above, both
provide a so-called ‘Finish Nailer’ for second-fixing
operations and a ‘Framing Nailer’ (that holds larger
(b)
(c)
Figure 2.52 (a) Pneumatic Framing Nailer; (b) cordless
gas/battery Framing Nailer; (c) cordless battery-only
Finish Nailer
Nailing Guns
nails) for first-fixing operations. The third type (c) is
limited to only a second-fixing Finish Nailer that fires
16-gauge nails of 32 mm to 63 mm length.
The general features of these nail guns include a
rubber pad at the base of the nose of the Finish
Nailer, to eliminate bruising to the timber; small
spikes at the base of the nose of the Framing Nailer,
to locate its position and ensure no slipping when
firing at an angle; angled nail-magazines – holding
angled glue- or paper-collated strip nails – to enable
skew-nailing and fixing in confined areas; depthof-drive adjustment; a capability of firing up to
4000 fixings per battery-charge and between 850 and
1000 fixings per fuel cell for type (b), about 800 per
battery charge for type (c) and, of course, no limitation on the amount of fixings from the constant compressed air supply for type (a); a capability of fixing
at a speed of two to three nails per second, depending
on the fixing situation and the skill developed in the
use of the tool; the nails available for use in these guns
are smooth or ring-shank, in bright, galvanized or
stainless steel.
The nail guns suggested for consideration in type
(a) are 1) Ace & K’s Angle Finish Nailer, model TYI
261650AB, that fires 25 mm to 50 mm ⫻ 16 gauge
nails, for use in second-fixing operations and 2) Ace &
K’s Angle Framing Nailer, model TYI 10034FN, that
fires 50 mm to 100 mm heavy-gauge nails, for use in
first-fixing operations.
The popular models in type (b) seem to be 1) the
ITW (Illinois Tool Works) Paslode Impulse, cordless
Angle Finish Nailer, model IM65A (recently changed
in model-number-only from IM250A), that fires
32 mm to 63 mm ⫻ 16-gauge nails for use in secondfixing operations and 2) the ITW Paslode Impulse,
cordless Angle Framing Nailer, model IM350/90 CT,
that fires 50 mm to 90 mm heavy-gauge nails, for use
in first-fixing operations.
The model for consideration in type (c) is the
DeWalt 18 volt, cordless Angle Finish Nailer, model
DEW DC618KA, that fires 32 mm to 63 mm ⫻
16-gauge nails, for use in second-fixing operations.
2.20.2 Nailing Guns for Wood to
Hard-Surface Fixings
In the (a) and (b) types, there are also nailing guns
available which are capable of fixing relatively thin
timber (up to 20 mm thick) to hard surfaces such as
concrete, steel, masonry and blockwork, etc. One to
consider from each type is as follows:
●
(a) In the pneumatic nail gun range, there is the
Ace & K Multi T Nailer, model TYI 2.2–2.5/64T,
that fires 25 mm to 64 mm masonry-type nails into
●
31
sand-and-cement screeds, brick and blockwork.
This tool also uses 14 gauge nails, known as Maxi
Brads, for wood to wood fixings.
(b) In the cordless, gas/rechargeable-battery type
nail-gun range, there is the ITW Spit Pulsa 700P
nail gun, that fires special nails into concrete, steel,
hollow- or solid-brick. This tool has automatic
power-adjustment, a 20-nail magazine (with a
40-nail magazine accessory) and is capable of
650 fixings per fuel cell and 1000 fixings per
battery charge. The manufacturers claim that it
does not split concrete, has no recoil and makes
less noise.
2.20.3 Cartridge (Powder-Actuated)
Guns for Wood to Hard-Surface
Fixings:
Figure 2.53 Powder-actuated tool
Figure 2.53: These tools are of great value on certain
construction sites where they might be needed for
fixing larger sections of timber, steel sections and
anchors to in situ concrete, mild steel and brickwork.
They are actuated by an exploded charge of gunpowder when the triggered firing pin strikes a
loaded cartridge. The driven fixings are either special
steel nails or threaded studs. Originally, all fixings
from these tools were fired by the high-velocity principle, whereby the nail travelled along the barrel at a
velocity of about 500 metres per second. The nail,
travelling at such a speed, was potentially lethal; hazards such as through-penetration, free-flighting and
ricochets, could easily occur through fixing into thin or
weak materials, or striking hard aggregates or reinforcing rods.
Figure 2.54: To overcome these dangers, manufacturers developed the low-velocity principle in their
tools. This reduces the muzzle velocity from 500
metres to between about 60 to 90 metres per second
without any loss of power. This has been achieved
by introducing a piston in the barrel between the
32
Tools Required: their Care and Proper Use
(e)
Cartridge
Steel-washered nail
(f)
(d)
(a)
(c)
Barrel
Wall
Plastic-washered nail
(b)
Cartridge
Web
Piston
(b)
Timber ground
Figure 2.54 (a) High-velocity principle; (b) low-velocity
principle
cartridge at the rear and the nail in front. The nail,
supported and guided by the cartridge-actuated piston, safely ceases its journey forward at the same time
that the captive piston comes to rest.
The powder-actuated tool represented here is the
Hilti DX 460 with an MX72 magazine attached. This
tool has now replaced the long-established DX 450
model and is now fully automatic with nails in magazine strips of 10 (in nail-lengths of 14 to 72 mm) and
cartridges also in strips of 10. It has a universal piston
and less recoil for operator safety and comfort.
2.20.4 Cartridge Tool Fixings
Figure 2.55: There should be few problems if fixing
into mild steel, in situ concrete or medium-density
bricks such as Flettons, but difficulties will be experienced if attempts are made to fix into high yield steel,
cast iron, cast steel, glazed tiles, high-density precast
concrete, engineering bricks, soft bricks such as
London Stocks and most natural stones – all of which
may have to be drilled and anchored with some form
of bolt or screw fixing.
If cartridge-tool users are ever in doubt, it is usually
possible to arrange for a manufacturer’s representative
to visit a site to give advice and/or test materials for a
required fixing system.
The recommended allowances for penetration by
nail or stud are: steel, 12 mm; concrete, 20 to 25 mm;
(a)
(b)
(a)
Figure 2.55 (a) Fixings to concrete; (b) fixings to steel;
(c) cartridge strip; (d) magazine nail-strip; (e) nail for
concrete and masonry; (f) nail for steel
brickwork, 25 to 37 mm. Note that if the steel is
only 6 mm thick, 12 mm should still be allowed for
penetration, even though the point will protrude
through the steel. When fixing to the lower flange
of a steel ‘I’ beam, as illustrated, avoid central fixings
which might coincide with the web above. If
concrete is weakly compacted (less dense), use a
longer fastener.
To calculate the length of nail required for fixing a
timber batten or ground to concrete, deduct 5 mm for
countersinking of nail into 25 mm timber, add 20 mm
for minimum penetration, then adjust, if necessary, up
to the nearest available nail size.
Cartridges are colour-coded to denote their
strength, indicated by a touch of coloured lacquer on
the crimped end. For the Hilti DX 460 tool, the cartridges available are: Green ⫽ light strength, Yellow ⫽
medium, Red ⫽ heavy, Black ⫽ extra heavy.
Fixing too near the edges of base materials should
be avoided, or spalling may occur; minimum distances
should be: concrete, 75 mm; brick, 63 mm; steel,
12 mm. The minimum distance between fixings
should be: concrete, 50 mm; brick, 63 mm; steel,
20 mm. Avoid fastening into concrete when its thickness is less than 3 ⫻ length of fastener-penetration;
and avoid fastening into steel which is thinner than
the shank-diameter of the fastener.
Nailing Guns
2.20.5 Safety Note
●
The same general safety precautions used on mains
powered tools, including the protection of eyes and
ears, should be adhered to, as well as the following:
●
●
●
Carefully read all the instructions provided in the
manufacturer’s literature before using the tool.
Obtain thorough training in the safe use of the
tool, either from the manufacturer’s representative
or from a competent person who has received
training himself from the manufacturer.
●
33
Ensure that the tool is well maintained and regularly serviced, in accordance with the manufacturer’s recommendations.
Wear heavy-duty rigger gloves and good-quality
safety goggles (these are usually supplied by the
tool manufacturer).
When a battery pack reaches the end of its life
cycle and needs replacing, it should be fully discharged and disposed of safely or recycled via your
dealer. NEVER dispose of it in normal rubbishdisposal bins or on domestic waste-disposal sites.
3
Carpentry Fixing-Devices
3.1 INTRODUCTION
Knowing what fixings to use to fix timber together or to
other materials and surfaces such as walls, ceilings and
floors, etc, comes with few rules other than trade experience and is not normally specified by the architect or
structural engineer. However, there are some exceptions
to this, usually when structural stability is dependent
upon certain fixings. For example, the maximum spacing
of galvanized restraint straps at roof level is not determined by the carpenter who fixes them, but by British
Standards’ Codes of Practice and The Building
Regulations. The majority of fixings, therefore, are
determined by the carpenter and details of these will be
stated as we progress through each section of this book.
Fixing devices such as framing anchors, joist hangers,
restraint straps, metal banding and panel adhesive, will
also be detailed and dealt with in other chapters.
3.1.1 Modern Improvements
Fixing devices have improved with modern technology
in the last few decades and although nails (with some
changes in design) are still being driven in traditionally
by hammer, purposely-designed T-headed nails are also
being fired in by Strip or Coil Nailers (nail guns) using
glue- or paper-collated strips of nails (see chapter 2).
Screws have changed considerably with twin thread,
deep-cut thread and steeper thread angles extending
along the entire shank to provide a better grip and
speedier driving performance. They also now have at
least seven variations in slotted head-design, ranging
from the traditional straight-slotted head to the Torxor T Star-slotted head. With the revolutionary change
from hand screwdrivers to electric and cordless
drill/drivers, the development in slotted-head types
was necessary to create a more secure, non-slip driving
attachment. Improved slotted heads such as Uni-Screw
and Torx/T Star promote non-wavering driving
alignment, virtually eliminating so-called cam-out situations. Like nails, screws also come in collated strips
for use in mains powered, automatic-feed screwdrivers.
The screws for these drivers have a bugle-shaped head,
which is an innovative countersunk shape allowing
them to sit at the correct depth in plasterboard without
tearing the paper. These auto-feed drivers have been
marketed particularly for drywall operations – fixing
plasterboard to lightweight steel or timber studpartitions – but can be used on other repetitive screwing operations such as fixing sheet material to wood
floors prior to tiling, or sheet material to flat roofs
prior to felt or GRP roofing. For these operations, collated floorboard-screws, with ordinary countersunk
heads, are available.
3.2 NAILS AND PINS
●
Figure 3.1(a): Round-head wire nails are available
in galvanized, sherardized and bright steel; sizes
range from 25 mm ⫻ 1.80 mm Ø to 200 mm ⫻
8.00 mm Ø. The nail-sizes most commonly used in
first-fixing jobs such as roofing and stud partitioning are 75 mm ⫻ 3.75 mm Ø and 100 mm ⫻
4.5 mm Ø. In certain fixing situations, even when
using the softest of softwoods, splitting may occur
with such large diameter nails and it will be wise to
(a)
(b)
(c)
(d)
Figure 3.1 (a) Round-head wire nail; (b) lost-head wire
nail; (c) brad-head oval nail; (d) lost-head oval nail
Nails and Pins
●
●
●
rest the head of the nail on a hard surface and blunt
the point of the nail with a hammer. This helps to
push the fibres forward, instead of sideways in a
splitting action.
Figure 3.1(b): Lost-head wire nails are available
in galvanized, sherardized and bright steel; sizes
range from 40 mm ⫻ 2.36 mm Ø to 75 mm ⫻
3.75 mm Ø. The nail-sizes most commonly used
in first-fixing jobs are 50 mm ⫻ 3 mm Ø and
65 mm ⫻ 3.35 mm Ø for floor-laying with T&G
boards. The rare rule used here is that the nail
length should be at least two-and-a-half times the
thickness of the floorboard.
Figure 3.1(c): Brad-head oval nails are available in
galvanized, sherardized and bright steel; sizes range
from 25 mm to 150 mm. The nail-sizes most commonly used in second-fixing operations, such as
fixing architraves and door stops, are 40 mm and
50 mm. The oval shape reduces the risk of splitting,
but the sharp point of the nail may still need to be
blunted in certain situations (for example, when
fixing the head of an architrave, near the mitre),
depending on the density of the timber.
Figure 3.1(d): Lost-head oval nails are available in
bright steel; sizes range from 40 mm to 75 mm. As
at (c) above, the nail-sizes most commonly used are
40 mm and 50 mm for fixing architraves, etc. The
advantage that these nails have over the brad-head
oval nails is that they are much easier to punch in
below the surface, as the nail punch is seated on a
flat head, rather than a thin-ridged head.
(e)
●
inner-skin walls changed to lightweight foamed
building blocks, such as the original Thermalite
blocks, direct fixings were still successful; but with
the introduction in recent years of ultra-lightweight
and high-thermal foamed blocks – which either do
not hold or will not accept unplugged, direct cutclasp-nail fixings – these nails lost their original
advantage and were superseded by other fixings.
However, because of their good holding-power and
direct-fixing ability, they are still very useful in
fixing temporary work (i.e. datum battens and cut
stair-strings, etc) to the joints of brickwork.
Research indicates that they are also being used for
their original fixing uses in the large number of old
properties undergoing modernization and conversion. The nail-sizes most commonly used seem to
be 50 mm, 75 mm and 100 mm.
Figure 3.2( f ): Cut floor brads in black iron; sizes
range from 50 mm to 100 mm. As the name
implies, these traditional nails are for fixing floorboards and, like cut clasp nails, they are still being
used in refurbishment work on old properties. (A
local supplier claims that they sold 2,300 kilos of
the 50 mm size last year!) On new-build projects,
however, cut floor brads have been superseded by
lost-head wire nails for fixing T&G floor-boarding
and annular-ring shank wire nails for fixing chipboard flooring panels – but only the latter type are
equal in holding power to cut floor brads. For this
reason, boards fixed with lost-head wire nails
should be nailed dovetail-fashion, as illustrated in
the chapter on flooring. The nail-sizes most commonly used seem to be 50 mm and 65 mm.
(f)
(g)
Figure 3.2 (e) Cut clasp nail; (f) cut floor brad
●
35
Figure 3.2(e): Cut clasp nails in black iron; sizes
range from 40 mm to 100 mm. In second-fixing
operations, these nails were originally used for fixing
skirting boards to wood-plugged mortar joints and
for making direct (unplugged) fixings into mortar
joints, soft Stock bricks and breeze blocks. When
(h)
(i)
(j)
Figure 3.3 (g) Annular-ring shank nail; (h) groovedshank nail; (i) panel pin; (j) masonry nail
●
Figure 3.3(g): Annular-ring shank nails are available in sherardized and bright steel; sizes range
from 20 mm ⫻ 2 mm Ø to 100 mm ⫻ 4.5 mm Ø.
The nail-sizes most commonly used seem to be the
36
●
●
●
Carpentry Fixing-Devices
65 mm ⫻ 3.35 mm Ø sherardized for first-fixing
operations such as the fixing of 22 mm thick windbracing to trussed rafters and the 50 mm ⫻
2.65 mm Ø bright steel nails for sub-flooring sheet
materials.
Figure 3.3(h): Grooved-shank nails are available in
galvanized steel; sizes are 40 mm, 50 mm, 60 mm,
75 mm and 100 mm. These newly marketed nails
have four fluted grooves around the shank, running
along their entire length. They are claimed to provide excellent grip, lighter weight – and therefore
produce more nails per kilo when compared with
round-head wire nails. Made from high grade steel,
BBA tested, they are also claimed to be bendresistant.
Figure 3.3(i): Panel pins are available in sherardized and bright steel; sizes range from 15 mm to
50 mm. The sizes occasionally used in secondfixing carpentry are 20 mm and 25 mm ⫻ 1.4 mm
Ø, 30 mm and 40 mm ⫻ 1.6 mm Ø, for fixing
small beads and thin panels, etc.
Figure 3.3(j): Masonry nails in zinc plated and
phosphate finish hardened steel; available sizes are
25 mm ⫻ 2.5 mm Ø, 40 mm, 50 mm, 65 mm and
75 mm ⫻ 3 mm Ø and 100 mm ⫻ 3.5 mm Ø.
These nails are useful if fixing into sandand-cement rendering and screeds, mortar joints
and high-thermal foamed blocks – but will not
penetrate concrete or hard bricks like Flettons.
3.3 SCREWS AND PLUGS
(a)
(b)
(c)
(d)
(e)
Figure 3.4 (a) Flat countersunk head; (b) raised
countersunk head; (c) round head; (d) bugle countersunk
head; (e) double-pitched countersunk head
Figure 3.4(a)(b)(c)(d)(e): Screws are sold in cartons or
boxes of 100 and 200 (and smaller amounts in packages
for DIY jobs) and are referred to by the amount required,
the length, gauge, head-type, metal-type/finish and
driving-slot type, usually in that order – by carpenters –
although screw-suppliers put the gauge before the
length. As illustrated, the three most commonly used
head-types in carpentry are (a) flat, countersunk (CSK)
head, (b) raised (RSD), countersunk head and (c) round
(RND) head. Two new heads recently added to the
conventional flat, countersunk-head type are (d) bugle
countersunk head and (e) the double-pitched countersunk
head. The raised or round part of the head is not included
in the stated length. The lengths of screws generally
range from 9 mm (-38 ⬙) to 150 mm (6⬙), but only relatively
short screws are available in RSD- and RND-head
types. CSK screws predominate for their structural use;
RSD- and RND-head screws are mostly used for fixing
ironmongery. The different types of metal and treatedfinish used (either for strength, cost, visual or anticorrosion reasons) include: steel (S), galvanized steel (G),
stainless steel (SS), bright zinc-plated (BZP), zinc and
yellow passivated (YZP), brass (B), sherardized (SH),
aluminium alloy (A), electro-brassed (EB), bronze (BR),
black phosphate (BP) and black japanned ( J). Most of
the abbreviations given here are used in supplier’s
catalogues and sometimes on the screw-box labels.
3.3.1 Defining the Gauge of a Screw
The gauge of a screw refers to the diameter of its
shank. Traditionally, this was stated as a number from
0 to 50 and indirectly related to an engineering wiregauge size in thousandths of an inch. The diameter of
the screw’s head is determined by the screw’s gauge –
and carpenters often need to know the head size to
ensure that screws will fit correctly in countersunk
holes in ironmongery such as butt hinges, where the
flat-headed screw should sit flush or slightly below the
surface. So, simple formulas evolved to determine the
obscure numbered gauge. One such formula was to
measure across the screw’s head or the countersunk
hole in sixteenths of an inch, double the figure and
subtract two. For example, a head or countersunk hole
measuring five sixteenths ⫽ 5 ⫻ 2 ⫽ 10 minus
2 ⫽ No. 8 gauge.
However, although some screws are at the moment
still being sold in imperial sizes with traditional gaugenumbers (for example, 1-43 ⬙ ⫻ 10 gauge CSK screws), the
majority of screws nowadays are in metric, both in
length and gauge. More than that, because most screwthreads have changed dramatically and are now protruding from the shank, instead of being cut into it, the
gauge often refers to the diameter across the screw
threads. An example, related to the one given above for
imperial sizes, would read: 45 mm ⫻ 5.0 mm gauge
CSK screws. This shows that if we were to double the
metric gauge-size, it would equal the imperial 10 gauge
example. However, this only works for gauge numbers 8
and 10. Another reasonably accurate way of finding the
imperial gauge-size – if required – is to measure across
the screw-head or the metal-countersinking in millimetres and the reading will approximate to the imperial
gauge, i.e., about 10 mm diameter ⫽ No.10 gauge. Or, if
the reading is divided by two, it will approximate to the
metric gauge required.
Screws and Plugs
3.3.2 Types of Driving Slot or Recess
(a)
(b)
(c)
(e)
(f)
(g)
(d)
Figure 3.5 (a) Straight slotted; (b) Phillips recess;
(c) Pozidriv recess; (d) Torx or T-Star recess; (e) Uni-Screw
recess; (f) Allen (Hex) recess; (g) square recess
Figure 3.5(a)(b)(c)(d)(e)(f )(g): Carpenters nowadays
need to carry a good-quality Screwdriver-Bits Set,
containing a quick-release bit holder and a set of
driver bits to cater for the majority of the following
variations in slotted/recessed head design: (a) Straight
slotted, (b) Phillips recess, (c) Pozidriv recess, compatible with Supadriv and Prodrive, (d) Torx or T-Star
recess, (e) Uni-Screw recess, (f ) Allen (Hex) recess,
(g) Square recess.
3.3.3 Conventional, Twinfast and
Superfast Screws
37
(a) Conventional, single-thread (single-start) screws
are comprised of a single spiral thread that takes
up two-thirds the length of the screw. The
remaining unthreaded shank has a diameter equal
to, or slightly larger than, the major diameter of
the thread. Because of this, these screws often
require a shank hole and a smaller pilot hole to be
drilled into timber to timber fixings.
(b) Twinfast, double-thread (double-start) screws are
comprised of a twin, parallel, spiral thread that
either takes up the entire length of the shank – for
increased holding-power in man-made materials
such as chipboard – or – above a certain length of
screw – has a portion of unthreaded shank left
under the head. The diameter of the remaining
shank is smaller than the thread, so there is a
reduced risk of splitting the timber near edges,
etc. Also, this feature makes separate shank-andpilot-holes redundant, as only one shank/pilot
hole is required when there is a need to drill.
(c) Superfast screws have additional innovative features other than the steeper, twin thread that pulls
the screw in faster with less effort. These include a
sharper, deeper-tread thread for increased holding-power; a specially designed self-drilling,
sharp-cutting point for easier location and to
enable screwing without (in some cases) the need
to drill a pilot hole; specially hardened and heattreated steel with screw-heads as strong as the tip
of the driver bit. Other features available on this
type of screw are: specially designed, rifled shanks
with an indented spiral that adds to the drill-like
cutting and screwing action; double-pitched
countersunk heads, giving more torque and
strength; self-countersinking ribs that protrude on
the underside of the countersunk head.
3.3.4 Screwing
(a)
(b)
(c)
Figure 3.6 (a) Conventional, single-spiral thread;
(b) twinfast, double-spiral thread; (c) superfast, doublespiral thread with extra features
Figure 3.6(a)(b)(c): In engineering terms, woodscrews
have spaced threads and are grouped into three types:
(a) Conventional, (b) Twinfast and (c) Superfast
(Supafast).
Figure 3.7(a)(b): When screwing items of ironmongery to timber, in most cases only a small pilot hole is
required and can easily be made with a square-tapered
shank, birdcage awl. When pushed into the timber and
turned ratchet-fashion, it will ream out the fibres
(unlike a brad-headed awl, which will push them
aside). Drilled pilot holes, if preferred, should be
about one-third smaller than the average diameter of
the threaded shank. If using conventional screws when
fixing timber to timber, a countersunk shank-hole
(also called a clearance hole) and a smaller pilot
(thread) hole, as illustrated, may be required.
Depending on the density of the timber, often the
small pilot/thread hole can be omitted. When using
Twinfast or Superfast screws with screw-threads protruding from the shank, as opposed to being cut into
38
Carpentry Fixing-Devices
(a)
(b)
them, only a single, combined shank/pilot hole may be
necessary, as illustrated.
When using powered or cordless drivers, always
start with a low torque setting and adjust it gradually
to bring the screw flush to the surface. Further screw
fixings of the same type, in the same area should be
possible without altering the final torque setting. If
using brass screws (for example, with brass butt
hinges), it is a wise practice to use steel screws first,
then replace them with the brass screws. This greatly
reduces the risk of these soft-metal screws snapping
under pressure. Alternatively – or additionally – rub
beeswax, candle wax or tallow on the thread to reduce
the tension on the screw.
3.3.5 Wall Plugs
(a)
(b)
(c)
Figure 3.8 (a) 40 mm ⫻ 8 mm Ø brown-coded
polythene plug; (b) 35 mm ⫻ 6 mm Ø red-coded
polythene plug; (c) 40 mm ⫻ 8 mm Ø grey-coloured
nylon plug
Figure 3.8(a)(b)(c): Plastic wall plugs have been the
foremost screw-fixing device for many years now (at
least three decades) and are extremely reliable if used
properly when fixing timber or joinery items, etc., to
solid walls. They are either made of high-density
polythene or nylon. The nylon types are usually greycoloured. The polythene types are colour-coded in
Figure 3.7 (a) Preparation
for conventional screws;
(b) preparation (where required)
for Twinfast-threaded screws
relation to their screw-gauge size. The size of masonry
drill required is given with each group of plugs –
although I would be wary of these recommendations
and have often found that, on certain ‘soft’ walls, a
smaller drill was better suited to a particular plug. The
coding is: Yellow ⫽ gauge No.4 and 6; Red ⫽ guage
No.6, 8 and 10; Brown ⫽ gauge No. 10, 12 and 14;
Blue ⫽ guage No.14, 16 and 18. In my experience, the
most common colour-coded plugs used in secondfixing carpentry are brown, which are 40 mm
long ⫻ 8 mm Ø, and red – of less use – which are
35 mm long ⫻ 6 mm Ø. If plugs of a certain gauge are
required to be longer, to suit the characteristics of the
wall and/or the length of the screws required, long
strips of polythene plug-material can be purchased
and cut to size by the user. These plastic strips are
colour-coded as follows: White ⫽ screw gauge 4 to
6 mm, drill size ⫽ 8 mm Ø; Red ⫽ screw gauge 7 to
8 mm, drill size ⫽ 10 mm Ø; Green ⫽ screw gauge 9
to 10 mm, drill size ⫽ 12 mm Ø; Blue ⫽ screw gauge
11 to 14 mm, drill size ⫽ 16 mm Ø.
Finally, plastic-strip plugs tend to rotate more easily
than purpose-made plugs – and for this reason they
must fit snugly in the plugged wall; some wall plugs
have a small, flexible barb projecting from each side,
like the head of an arrow, to create an initial anchorage
in the plugged wall. This allows the screw to be turned
without the negative effect of rotating the plug.
3.3.6 Plugging the Wall
Figure 3.9(a)(b): When fixing to traditionallyplastered walls of so-called float-render-and-set finish,
it is important that the fixing has at least 50% of its
wall-depth anchored in the underlying brickwork or
blockwork. This is especially so in older-type properties where the plasterwork is relatively soft. If you
have marked the wall through shank holes drilled in a
piece of timber or in a joinery item prior to plugging,
mark these points further with a pencilled cross, so
that they can be used as cross-sights when drilling. Be
prepared to control the drill to keep on target. It can
Screws and Plugs
39
3.3.7 Nylon-Sleeved Screws
(a)
(b)
(a)
(b)
(c)
Figure 3.9 (a) Plastered wall drilled ready for plugging;
(b) exaggerated effect of plug-expansion to highlight
good anchorage beyond the plastered surface
be done – about 90% of the time! The procedure is as
follows:
●
●
●
●
●
Select the required size of tungsten-carbide tipped
masonry drill and secure it in your rotary hammer
drill (see drill-types described in chapter 2).
Work out the amount of screw that should be in the
wall as per the following example: If fixing a 19 mm
thick timber shelf-bearer to a solid wall, plastered
with 15 mm thick, relatively soft Carlite plaster, the
length of screw in this situation should equal at least
3 times the bearer thickness, making it 19 ⫻ 3 ⫽ 57.
The nearest screw is 60 mm and if we use a No. 12
gauge CSK screw and a brown-coded plug, which is
40 mm long, we have 60, minus 40, leaving 20 mm.
This is 1 mm more than the bearer thickness, so we
must allow the screw to go through the plug by this
amount. In practical terms, we need to increase this
by, say, another 4 mm (to accommodate any trapped
debris in the plug hole and to allow for any undersurface countersinking). So we have 60 minus
19 ⫽ 41 ⫹ 4 mm tolerance ⫽ 45 mm drilling depth.
If you drill slightly more than this depth, it is not
critical – but if you drill excessively more, you run the
risk of the plug being pushed in too deeply by the
screw.
Wrap a piece of masking tape round the drill bit to
determine the depth (or set the depth-gauge
attachment on the hammer drill); wear your
safety goggles, hold the drill visually square to the
wall – vertically and horizontally – and start
drilling.
When deep enough, relax the pressure and with the
drill rotating negatively, quickly work it in and
out of the hole for a few seconds to clear the
debris.
Drill all the required holes in a similar way and,
when finished, insert the plugs flush to the wall.
You are now ready for screwing.
Figure 3.10 Sleeved screws: (a) Frame-fix screw;
(b) hammer-fix screw; (c) window-fix screw
Figure 3.10(a)(b)(c): Nylon-sleeved (grey coloured)
Frame-fix, Hammer-fix and Window-fix screws are
popular nowadays. They provide the advantage of
enabling a door frame or lining, a window frame, a
kitchen unit or whatever else, to be fixed whilst the
item is in the required fixing-position. There is no
need to mark and plug the wall separately. This is
achieved by drilling through the pre-positioned
joinery-item and the wall in one operation. Then the
sleeved Frame-fix, Hammer-fix or Window-fix screw
is inserted as a one-piece, combined fixing. Once
located in the two aligned holes, the protruding
screw-head is either screwed in or driven in by hammer, according to the type of fixing used. If necessary,
all three types can be unscrewed once fixed.
The Frame-fix and Hammer-fix types work on the
principle of the screw being driven into a decreasing,
tapered hole in the nylon sleeve, which causes the end
portion to expand out into an alligator shape, creating
excellent anchorage. The Window-fix screw works on
a similar principle, except that the alligator effect is
achieved by a tapered, cork-shaped nylon-end being
pulled up into the sleeve when the screw is tightened.
It has to be said that the Frame-fix and the
Window-fix screws seem to achieve more holding
power than the Hammer-fix type.
Although the through-drilling is described as one
operation, in practice it should be two. First, the joinery item is drilled through with a twist drill (carefully
stopping short of piercing the wall), then the job is
completed by switching to a masonry drill which is
equal in diameter to the twist drill.
3.3.8 Frame Screws
Figure 3.11: So-called Frame screws are now available
and are described as a masonry screw for fixing into
‘most substrates’. No plugs are needed, but a 6 mm Ø
pilot hole must be drilled through the frame into the
40
Carpentry Fixing-Devices
●
Figure 3.11 Non-sleeved, self-tapping Frame screw
concrete, brickwork, etc. The gauge of these screws is
7.5 mm, which means that 0.75 mm of thread cuts
into the 6 mm hole in the substrate to create its own
mating thread and fixing. These screws are zinc plated
and yellow passivated, with T30 Star-drive recesses.
Their lengths range from 42 mm to 182 mm in increments of 20 mm up to 122 mm, then 30 mm up to
182 mm. White or brown T30 plastic caps are available for these screws, if required.
●
●
3.4 CAVITY FIXINGS
(a)
(b)
(d)
(c)
(e)
Figure 3.12 (a) Plasplugs Super Toggle Cavity Anchor;
(b) Plasplugs Plasterboard Heavy-Duty Fixing; (c) Fischer
Plasterboard Plug; (d) Nylon or Metal (zinc-plated) EasiDriver; (e) Rawlplug ‘Uno’ Plug
Figure 3.12(a)(b)(c)(d)(e): Cavity Fixings are used to
create reliable fixings into hollow walls and ceilings.
Therefore, the so-called substrate is usually plasterboard, of which there are two thicknesses: 9.5 mm and
12.5 mm. However, they may be used for fixings into
any other relatively thin lining material. With the
introduction of dry-lined walls more than two decades
ago – which have now mostly superseded solid-plastered walls – there has been more demand for this type
of fixing and most manufacturers have risen to this
with a wide variety of different devices now on the
market. Because of this large selection, only five types
that seem to be popular, will be covered here:
●
(a) Plasplugs Super Toggle Cavity Anchors are
made of nylon and are self-adjusting to lining
thicknesses of between 7 and 14 mm. The nylon
anchor-arms are drawn up to the back of the plasterboard as the screw is tightened. A 10 mm Ø hole
●
is required to accommodate the plug, which takes a
No.8 gauge screw.
(b) Plasplugs Plasterboard Heavy-Duty Fixings
provide an extra strong expanding grip with their
multiple barbs and screw-tensioning calliper
anchors. These are squeezed in when inserting the
plug through a 10 mm Ø hole and – like the above
plug – are drawn up to the back of the plasterboard
as the No.8 gauge screw is tightened.
(c) Fischer Plasterboard Plugs are made of nylon
to provide a short expansion zone to take high pullout loads. There are two sizes; one requires a 8 mm
Ø hole and takes a 4 mm gauge (No.8) singlethread screw, the other requires a 10 mm Ø hole
and takes a 5 mm gauge (No.10) single-thread
screw.
(d) Nylon and Metal (zinc-plated) Easi-Drivers
provide rapid and effective fixings into plasterboard, without the need for drilling separate location holes. The screw-fixing itself acts as a pilot
drill, cutting-thread and securing-thread. They are
driven easily into the plasterboard by using a crosshead screwdriver or a powered Pozidriv bit. The
metal Drivers are more suitable for heavier loads
than the nylon Drivers. They are supplied with
screws, but their limitation, in carpentry terms, is
that the maximum fixture-thickness recommended
by the manufacturers is 10 mm for nylon Drivers
and 15 mm for metal Drivers.
(e) Rawlplug ‘Uno’ Plugs have a universal function. Their patented zigzag expansion pattern
allows them to form a secure fixing into hollow
walls, or any other type of wall, ceiling or floor.
They are suitable for all light to medium weight
applications and are colour-coded in Yellow, Red
and Brown for screw gauges ranging from 3.0 mm
to 6.0 mm, with plug lengths of 24, 28, 30 and
32 mm. Corresponding drill-holes are 5, 6, 7 and
8 mm diameter.
Two final points on this subject are, (1) it should be
remembered that when fixing fixtures to a plasterboarded, stud-partition wall, or a plaster-boarded ceiling, there are concealed studs or joists which would
provide excellent fixings – if the fixture happened to
coincide with them, or if the fixture’s position was not
critical and could be altered to suit them; (2) Nylonsleeved Frame-fix and Window-fix screws make a very
good alternative heavy-duty fixing for use on drylined block walls. This is because they can bridge the
small cavity behind the plasterboard and take their
anchorage from being drilled and fixed into the
blockwork.
4
Making a Carpenter’s
Tool Box
4.1 INTRODUCTION
Apart from cordless and powered tools, the large
number of hand tools that carpenters need to perform
their trade, demands some kind of box or bag in
which to store them between jobs, or in which to
transport them when moving around. Nowadays, bags
(basses) and holdalls are more popular for fitting into
vans and the boots of cars, and tool boxes, as such, are
not used on site. However, the carpenter’s tool box is
still a better container for hand tools, if only to be left
at home for storage, while a holdall conveys requiredtools back and forth to the workplace.
the inside top of the box. This is supported by
20 ⫻ 9 mm finished hardwood side runners, glued and
pinned or screwed to the sides of the box with
-34 (18 mm) ⫻ 6 countersunk screws, two each side. The
tray, with dovetailed corners and 6 mm thick crossdivisions, is made up from 70 ⫻ 9 mm finished softwood and a 4 mm plywood base.
178 O/A
800 mm
Tray
38
400
65
4.2 CONSTRUCTION
65
CL
80
Traditionally, the design and construction of this box
was made up as follows.
End elevation
Front elevation
Section
4.2.1 Carcase
Figure 4.1: This comprises the top, bottom and side
material, which should be of selected softwood, straightgrained and free from large knots and other defects. To
keep the weight of the box to a minimum, the finished
thickness should be 13 mm, the width – ex 175 mm –
finished to 170 mm. The corners of the carcase should
be formed with through-dovetail joints, glued together.
4.2.2 Cladding
The front and back of the box should have 4 mm thick
plywood glued and pinned to its edges.
Tail
Pins
4.2.3 Tray
A shallow tray or drawer, for holding small tools –
especially edge-tools such as chisels – is made to fit
Figure 4.1 Traditional tool box
42
Making a Carpenter’s Tool Box
4.2.4 Hinge Fillets
Divider steps
These are glued and pinned to the inside faces of the lid
and box to complete the structure and accommodate
the hinges. They should be made from at least
28 ⫻ 16 mm finished softwood.
1
2
3
4
5
51/2
cL
6
First setting
4.2.5 Fittings
These comprise 1-12 pairs of 50 or 63 mm butt hinges or
a continuous strip hinge, sometimes referred to as a
piano hinge, a case handle with small bolts, case clips
(one pair) and box lock or, alternatively, a padlock and
hasp and staple of 75 mm safety pattern type.
Divider steps
51/2
5
4
3
2
1
6
Second setting
4.2.6 Construction Details
There is a traditional method for setting out dovetails,
but the one described here, developed through an
attraction to geometry some years ago, is preferred
and recommended for its simplicity and speed when
making dovetails by hand.
After cutting up the carcase material squarely with a
panel saw to the length and height of the box, with an
allowance of 2 mm (1 mm each end) on each of the
four pieces, mark the thickness of the material, plus the
allowance, 13 1 mm, in from each end on two pieces
only, one long and one short. Square these around the
material (face, edge, face, edge) with a sharp pencil.
Mark the other two pieces of carcase from the two
already marked. These marks are called shoulder
lines.
4.2.7 Forming Through-dovetails
Figure 4.2: The sides of the box are now ready for
dovetailing. First, select the best face-side and mark
a centre line across the width, between the shoulder
and the end of the timber. This line is used to plot
the dividing points for the tails. Now decide how
many dovetails are required and obtain a pair of sharp
dividers or a pair of compasses. If you decide – on this
width – to have 5, as illustrated, the dividers must be
stepped out by trial-and-error stepping, 5 -12 steps from
one edge and 5 -12 from the other, i.e. left to right along
the centre line, then right to left. The sixth stepping,
when one point of the dividers is off the timber, over
the edge, allows visual judgement to be made as to
whether half a step, more or less, has been achieved. If
under half-a-step is over the edge, try again; if slightly
over, you could try again or let it go. (Letting it go will
result in slightly wider dovetails.)
W
51/2 DS
(W = width; DS = divider steps)
W
41/2 DS
W
11/2 DS
Alternative setting out to give
double-width pin for lid-cut
1:6 ratio
Figure 4.2 Setting-out details
4.2.8 Dovetail Angle and
Setting-out Method
The dovetail angle for softwood is usually set to a
ratio of 1:6. This can be set up on a sliding bevel by
alignment to a right-angled line across a board which
has been marked 6 cm across and 1 cm along the edge.
The bevel is now used to pick up the divider-points
along the centre line and the dovetail angles are
marked with a sharp pencil.
The easiest way to think of the setting-out method,
is to remember that -12 a divider step more than the
number of dovetails is required, i.e. 1 dovetail, 1-12
divider steps (or spacings) across the timber; 2 dovetails, 2-12 spacings; 3 dovetails, 3-12 spacings, etc. If
larger dovetails than pins are required by this method,
as shown in Figure 4.6, simply step out the dividers
until much less than half a step remains at the edge.
4.2.9 Cutting the Tails and Pins
Next, square the tails across the top edge of the end
grain, cut carefully with a fine saw (preferably a
Construction
dovetail saw, but a tenon saw will suffice), remove the
outer shoulders with the same saw, the inner shoulders
with a coping saw and bevelled-edge chisels. Hold
each joint together and mark the tails onto the endgrain. Square these lines onto the faces of the bottom
and top of the box. Remember that it is the dovetail
shapes that are now removed, and repeat the cutting
operation for the pins as for the tails.
43
Gauge line for lid-cut
Quadrant shapes cut prior to ply-cladding
4.2.10 The Need for Speed of
Assembly
Figure 4.5 Quadrant shapes cut prior to ply-cladding
The thin carcase material is very prone to distortion
across its width, known as cupping, especially if the
growth rings are tangential to the face, as shown in
Figure 4.3. For this reason, the joints should be
formed as quickly as possible and the carcase glued
together and checked diagonally for squareness, as in
Figure 4.4. If the dovetails are a snug fit, there should
be no need for the box to be held together with
cramps while the glue is setting.
quadrant shape 80 mm up from the base. This quadrant shape only, should be cut on each side with a coping saw before cladding.
4.2.12 Applying the Cladding
The 4 mm thick plywood for the front and back, having been cut slightly oversize by a few millimetres, is
then glued and pinned with 18 mm panel pins at
approximately 75 mm centres (c/c) into position,
transforming the assembly into an inaccessible box.
The box is then cleaned up with a smoothing plane to
a flat finish all round and sanded.
4.2.13 Releasing the Lid
Figure 4.3 Cupping of carcase material
By careful use of a tenon saw (or a finely set panel
saw) working from each top corner, across the top and
down the sides to meet the pre-cut quadrants, then
across the plywood front, the lid is cut and released.
The hinge fillets, including the end-grain abutments,
are then glued into position and pinned through the
face of the ply (Figure 4.6). When set, the lid can be
hinged to the box, after cleaning up all the sawn edges
with glass paper only – no planing!
⊕
Figure 4.4 Checking the box for squareness: check both
diagonals with stick; if two marks * are recorded, distort
the structure until the centre of these marks registers on
both checks
4.2.11 Preparation for Cladding
Figure 4.5: After the glue has set, a gauge line
representing the eventual edge of the lid, can now be
marked – or may have been marked earlier to assist in
setting out the dovetails – and should terminate as a
4.2.14 Adding Fittings and the Tray
The handle, bolted not screwed, case clips and hasp
and staple can now be fitted. First, to help transfer the
weight of a full box to the lid, when lifted, a minimum
35 ⫻ 7 mm hardwood fillet should be glued and
screwed up to the underside lock-edge of the box,
projecting about 6–9 mm into the lid area, as seen in
Figure 4.l.
Finally, again using through-dovetails, or simple
cross-rebates (Figure 4.6), the tray is made with one
or two cross-divisions, to the inside length minus
2 mm for sliding tolerance. Turn-buttons for saw handles (Figures 4.1 and 4.6) can be made and glued to
the lid to hold at least two saws.
44
Making a Carpenter’s Tool Box
100 mm
Turn-button to fit saw
handle, made from hardwood,
thick enough to allow the 5 mm
button to be sawn off after
shaping
Cross-rebates to drawer corners
as an alternative to dovetails
19 mm diameter hole as
drawer-pull at each end
Stub-tenoned hinge fillets glued into position
when carcase is formed, prior to plycladding, as an alternative to
insertion of butt-jointed fillets
after cladding
Saw-cut gap
2
3
4
5
6
X
cL
Coping-saw cut
Temporary support
to fillets whilst gluing
and pinning plywood
Figure 4.6 Alternative details
1
11
10
9
8
7
If small pins and wide dovetails are preferred,
distance X on divider-step 6 must be over half a step
(divider-steps 7 to 11 marks the L/H side of the tail)
5
Making Builder’s Plant
for Site Use
5.1 SAW STOOL
5.1.1 Introduction
Apart from metal- and plastic-versions now available,
a wooden saw stool, sometimes called a saw horse or
trestle, has few variations in design, but the one shown
in Figure 5.1 is most commonly used. The length and
height can vary, although the height should not be less
∗Leg-arris length
∗
than that shown, otherwise on hand rip-sawing operations (still done occasionally on short lengths of
timber) – when the saw should be at a steep angle
of about 60–70⬚ – the end (toe) of the saw may hit
the floor.
5.1.2 Material Required
The material used is usually softwood and can be a
sawn finish or planed all round (par). The latter reduces
the risk of picking up splinters when handling the
stool. Material sizes also vary, often according to what
may or may not be available on site, or, for design reasons, in consideration of the weight factor of the stool.
Typical sizes for a sturdy stool are given in the
illustrations, showing the top as ex. 100 ⫻ 50 mm, legs
ex. 75 ⫻ 50 mm, end-cleats 6, 9 or 12 mm plywood
or MDF board.
5.1.3 Angles of Legs
The angles of the legs are not critical to a degree and
are usually based on the safe angle-of-lean used on
ladders, which is to a ratio of 4 in 1 (4:1). This refers
to a slope or gradient measured by a vertical rise of
four units over a horizontal distance of one unit. This
ratio works out to give approximately 76⬚.
700
100
95
100
5.1.4 Optional Nail-box Facility
45
532
End
cleat
70
45
Side
elevation
End
elevation
Figure 5.1 Isometric view of a typical carpenter’s saw stool
Some tradespeople used to incorporate a tray within
the leg structure, to act as a nail box. The tray, which
was sub-divided to contain a variety of nails, screws,
etc., had shallow sides of about 50–75 mm depth,
plywood base and was usually fixed halfway up the
legs on cross or longitudinal bearers. The advantages
of this combined stool/nail box were outweighed by
the increased weight factor, restricted access to nails,
trapping of sawdust and cleaning-out difficulties.
46
Making Builder’s Plant for Site Use
5.1.5 Need For Geometry
100
100
By following very basic criteria and guesswork, saw
stools are often roughly made without any regard for
the simple geometry involved. This is partly to save
time, of course, but also reflects a lack of knowledge of
the subject. Making a saw stool should be a quick and
simple operation, joinery and geometry-wise (it can be
done in about an hour).
Vertical
height (vh)
= 532 mm
5.1.6 Length of the Leg
Before metrication of measurement in industry, the
height of saw stools ranged between 21 and 24 in. The
approximate metric equivalent is 532 and 610 mm.
The lesser height is used here for preference. Once the
vertical height has been decided, the length of the legs
has to be worked out. Basically, without the necessary
additional allowances, this is a measurement along the
outside corner of the leg (indicated in Figure 5.1 with
an asterisk) known as the leg-arris length (arris is a
French/Latin-derived word used widely in the trade
to define sharp, external angles).
Base
Base
Side
elevation
532 vh
5.1.7 Determining Leg-arris Length
The leg-arris length can be worked out in three
different ways. These different methods are (A) by
practical geometry, (B) by drawing-board geometry
and (C) by a method of calculation. Only method (A)
is used here.
By Practical Geometry
Finding the leg-arris length by this method is based
on the fact that a piece of timber leaning at an angle,
like the hypotenuse of a right-angled triangle, has a
vertical height and a base length. Once the measurement of the base and height are known, the length of
the timber (on the hypotenuse) can be worked out.
These theoretical triangles must first be visualized on
the side and end elevations, as illustrated in Figure 5.2.
Knowing that the vertical height (vh) is to be 532 mm
and the leg-angle is 4 in 1, the base measurement is
worked out by dividing vh by 4, i.e.
vh
532
⫽
⫽ 133 mm
4
4
Using Base Measurements
Figure 5.3: Now that the base measurement of the side
and end elevation triangles is known to be 133 mm,
this information can be used to find the unknown base
measurement of the leg-arris triangle. Because the leg
is leaning at the same angle in both elevations, the
Base
Base
End
elevation
Figure 5.2 With 4 in 1 leg-angle, the base equals
vh ⫼ 4 ⫽ 532 ⫼ 4 ⫽ 133 (base measurement ⫽
133 mm)
leg-arris base must be a 45⬚ diagonal within a square
of 133 ⫻ 133 mm.
Finding Leg-arris Length
All that needs to be done now, therefore, is to form a true
square with these measurements, draw a diagonal line
from corner to corner and measure its length. The product is the base measurement of the leg-arris triangle.
This measurement is then applied to the base of another
right-angled setting out, the stool’s vertical height is
added, and the resultant diagonal on the hypotenuse
measured to produce the true leg-arris length.
Practical Method
Figure 5.4: Two practical ways of doing this are to use
a steel roofing square (now called a metric rafter square
by manufacturers), or to use the right-angled corner of
a piece of hardboard or plywood.
Saw Stool
47
Plan view of
leg-arrises
133
Leg-arris
triangle
133
a
c
b
133
Metric rafter
square (620 ⫻ 450 mm)
Hardboard
or
plywood
Blade
Gives c (188 mm)
b
b
Tongue
Gives c (188 mm)
c
133
at the bottom, cutting tolerance has to be added to the
leg as an allowance for the angled setting out involved.
The length of legs, therefore, equals the true leg-arris
length, 564 mm, plus 46 mm tolerance, equals 610 mm.
5.1.9 Setting Up the Bevel(s)
b
Gives d (564 mm)
b
Figure 5.3 Base measurements,
133 ⫻ 133 mm, forming a
square, give required diagonal
base-measurement of leg-arris
triangle c
b
(a)
a
d
Gives d (564 mm)
a
c
(b)
Figure 5.4 (a) Set b on each side and measure the
diagonal c (b) Set c and a on each side to find length of d
As illustrated, the base measurement b of 133 mm is
set on each side of the angle to enable the diagonal c,
the base of the leg-arris triangle, to be measured. This
measurement of 188 mm, forms the base of another
setting out on the roofing square or hardboard, in relation to the vertical height of the stool a, of 532 mm,
being placed on the opposite side of the angle. The
diagonal d is then measured to produce the true legarris length of (to the nearest millimetre) 564 mm.
5.1.8 Adding Cutting Tolerances
Now that the true leg-arris length has been determined
at least another, say 35 mm at the top, plus say 11 mm
Figure 5.5: The legs and stool top can now be cut to
length, ready for marking out. The marking out can
either be done with a carpenter’s bevel (or bevels), or
with a purpose-made template. As illustrated, the 4 in
1/1 in 4 angles are set out against the square corner of
a piece of hardboard, plywood or MDF board, to a
selected size. Sizes of 300 mm and 75 mm are advisable as a minimum ratio if the setting out is to be cut
off and used as a template in itself. If carpenters’
bevels are to be used, set up one at 4 in 1 and the
other at 1 in 4, as illustrated. If only one bevel is available, set and use at the 4 in 1 (76⬚) angle before resetting for use at the 1 in 4 (14⬚) angle.
5.1.10 Alternative Setting Out
Figure 5.6: This shows an alternative way of setting out
the two required angles, to enable a carpenter’s bevel to
be set up. First, mark a square line from point a on the
face of a straightedge or on the underside-face of the
stool-top material. Then, from point a, mark point b at
4 cm (40 mm) and point c at 1 cm (10 mm). Draw line
c through b to establish the first required angle of 4 in
1 (76⬚). From point a, mark point d at 1 cm and point
e from either side of a, at 4 cm. Draw line e through
d to establish the second angle of 1 in 4 (14⬚). The
advantage of setting out on the underside of the stool’s
top, is that the setting out will remain visible for years,
ready at any time for making the next stool.
48
Making Builder’s Plant for Site Use
Hardboard,
plywood
etc.
300 1:4
1:4
4:1
4:1
75
Figure 5.5 Mark 4 in 1/1 in
4 angle, set up bevels, or cut out
as template
5.1.13 Waste Material
Note that in Figure 5.7(b) the shaded areas represent
the timber on the waste side of the cut. Graphic
b
d
B
A
e
a
c
L/H leg
∗
∗
B
R/H leg
A
Figure 5.6 Alternative setting out
(a)
5.1.11 Marking Out the Legs
Figure 5.7(a): Before attempting to mark out the
birdsmouth cuts, it is essential to identify and mark
the starting point on each leg to avoid confusion.
As illustrated, this point is on each inside-leg edge,
about 6 mm down, and relates to the uppermost
point of the compound splay cut in relation to the
top surface of the stool. This mark is referred to as
zero point.
Zero
point
5.1.12 Two Slopes Down, Two
Slopes Up
Figure 5.7(b): From zero point, the 4 in 1 angle always
slopes down on edge A, turns the corner and, likewise,
slopes down on face-side B, turns again and this
time slopes up on edge C, and up on back-face D, to
meet the first point (zero) on face-edge A. So, on the
four sides of each leg, the marking sequence leading
from one line to the other, is two slopes down, two
slopes up, back to zero point on leg-edge A.
A
B
C
D
Elevation of R/H leg
birdsmouth development
D
A
C
B
(b)
Figure 5.7 (a) Marking out of legs starts from the points
marked*; (b) plan view of the marking sequence
Saw Stool
5.1.16 Use of Template – Second
Stage
demarcation such as this – but roughly marked – is
often used by carpenters and joiners to reduce the risk
of removing the wrong area of material.
5.1.14 Marking Zero-point Arrises
C
49
48 mm
12 mm
B
C
B
A
A
A
A
Figure 5.10 Marking out of the legs – second stage
Figure 5.10: Returning to surface A, the template is
again positioned and marked on the 4 in 1 angle, set
at 48 mm down, measured at right-angles to the first
line. This represents the stool-top thickness, 45 mm,
plus 3 mm to offset the fact that the stool-top thickness registers geometrically at a greater depth on the
4 in 1 angled legs. Next, measure 12 mm in on the top
line to represent the beak of the birdsmouth-cut and
use the 1 in 4 (14⬚) angle of the template to mark the
line as shown.
Figure 5.8 Marking zero-point arrises
The zero-point arris can be quickly determined on
each leg by placing the four legs together, with the
inside-leg edges and back-faces (A and D) touching,
and by marking the top corner of each leg on the middle intersection, as illustrated in Figure 5.8.
5.1.17 Use of Template – Third Stage
Figure 5.11: To complete the marking out of the first
leg, the lower line on surface A, representing the
stool-top thickness, is picked up on surface B by the
template and marked parallel to the line above. It is
picked up on surface C and again marked parallel to
the line above, then the 1 in 4 (14⬚) angle is marked in
at 12 mm to complete the beak of the birdsmouth
5.1.15 Use of Template – First Stage
Figure 5.9 : By using the template positioned on its 4
in 1 (76⬚) angle, surfaces A, B, C and D of the leg are
first marked as illustrated here and as described in
Figure 5.7(b).
A
A
A
B
B
C
C
D
D
Figure 5.9 Marking out of the
legs – first stage
50
Making Builder’s Plant for Site Use
12 mm
B
B
C
C
C
D
D
Figure 5.11 Marking out of the legs – third
stage
(this birdsmouth-marking is on the opposite side to
the one marked on surface A). Finally, the lip of the
birdsmouth is picked up from C and marked on surface D, yet again parallel to the line above.
5.1.18 Complete the Marking Out
Figure 5.13 Cutting birdsmouths to shape
A
A
B
C
C
B
Figure 5.12 The four legs marked out
Figure 5.12: As illustrated, complete the marking out
of the four legs, being careful to follow the marking
sequence already explained, i.e. slope down from zero
point on surface A of each leg to produce two opposite pairs of legs.
5.1.19 Cutting Birdsmouths
Figure 5.13: By using a suitable handsaw (a sharp
panel saw is recommended, as some hardpoint saws
are ineffective for ripping), the four birdsmouths
should be carefully cut to shape by first ripping down
from the beak and then by cross-cutting the shoulder
line on the lower lip. This can be done on a stool,
if one is available, or on any convenient cutting
platform – failing access to such equipment as a
joinery-shop vice, etc. The cross-cutting of the
shoulders can also – more accurately – be cut with a
tenon saw.
5.1.20 Checking Matched Pairs
Figure 5.14: After cutting, check that the legs match
in pairs and hold each birdsmouth against the side of
the stool-top material at any point to check the cut for
squareness. If necessary, adjust by chisel-paring; inaccuracies, if any, are usually found on the inner surface
of the end grain of the lower lip.
5.1.21 Marking Leg-housings
Figure 5.15: Next, as illustrated, the birdsmouthed legs
are held in position on the side of the stool top,
100 mm in from the ends, and the sides marked to
indicate the housings.
Saw Stool
51
with the aid of a mallet – onto a solid bench or
boarded surface from alternate faces of the stool top.
5.1.23 Alternative Leg-fixings
A
A
A
B
C
C
B
B
A
B
Figure 5.14 The completed, matched pairs
100
100
Figure 5.17 Alternative fixings
Figure 5.17: The stool top can now be set aside and
the legs prepared for fixings – if screws are to be used.
As illustrated, two or three fixings may be used and
these are usually judged rather than marked for position. However, for strength, the fixings should neither
be too near the edges nor too close together. Shank
holes should be drilled and countersunk for, say, 2
in ⫻ 10 gauge screws. If nails are used instead of
screws, 63–75 mm round-head wire nails are preferred.
Take care when screwing or driving-in fixings, to
ensure that they are parallel to the stool-top’s surface,
i.e. at a 4 in 1 angle to the surface of the legs.
Figure 5.15 Mark leg-housings
5.1.24 End Cleats
5.1.22 Cutting Leg-Housings
47
∗
∗
45
95
47
— = 11.75 mm +
4
∗
tolerance = 13 mm ⫻ 2
+ 95 = 121 mm
Therefore top of cleat = 121 mm
Figure 5.16: When marked and squared onto the facesides and underside, the housings are then gauged to
12 mm depth on both sides of the stool top, ready for
housing. The angled sides of the housings can be cut
with a tenon saw or panel saw and pared out with a
wide bevel-edged chisel. The recommended chiselling
technique, for safety and efficiency, is to pare down
(known as vertical paring) – either by hand pressure or
1
2
Figure 5.16 Gauge housings to depth, cut and pare out
with wide bevel-edged chisel
200
121
121
Figure 5.18 End cleats
Figure 5.18: To enable the assembly of the stool to
flow without interruption, it will now be necessary
52
Making Builder’s Plant for Site Use
to prepare the end cleats. By using the template
as illustrated, these can be set out economically on
board material or plywood and cut to shape with the
panel or hardpoint saw. The size and shape of the
cleats is critical, as the assembled legs are unlikely to
assume the correct leg-spread on their own and will
rely on the end cleats to correct and stabilize their
posture.
Common Error
It is a common error in stool-making to fix the legs
and mark the shape of the cleats unscientifically from
the shape of the distorted leg assembly. This is done
by marking the outer shape of the stool’s end onto the
cleat material laid against it.
5.1.25 Working Out Cleat Size
The setting out of the cleats, therefore, should be
marked from the template (or bevel) in relation to a
measurement at the top of the cleat. This measurement
is made up by the width of the stool top and the visible base of the birdsmouth beak on each side. This
can either be measured in position or determined by
dividing the 4 in 1 diagonal thickness of the stool
top by four. That is, as illustrated in Figure 5.18,
47 ⫼ 4 ⫽ 11.75 mm ⫻ 2 ⫽ 23.5 mm, plus width of
stool top (95 mm) giving 118.5 mm. Add 2.5 mm as a
working tolerance and for final cleaning up, therefore,
top of cleat equals 121 mm.
5.1.26 Fixing the Legs
Figure 5.20 Fix plywood cleats with 50 mm round wire
1
nails or 1–2 in ⫻ 8 gauge screws
stool top, then the cleats are nailed or screwed into
position, using 50 mm round-head wire nails or 1–12 in
⫻ 8 gauge screws. During the fixing operation, to
avoid weakening the leg connections, the stool should
be supported on a bench, as illustrated, or any other
suspended platform.
5.1.28 Removing the Ears and
Marking the Leg-waste
Figure 5.21: Next, the projecting ears are cut off
from the legs, with a slight allowance, say 1 mm,
left for planing to an even finish with the stool top.
After cleaning-up the top to a flat finish, measure
down each leg and mark the leg-arris length (previously determined) to establish the stool’s height. Join
these marks with a straightedge and mark the line of
feet on the ends and sides of the stool – or, if preferred, use the template or bevel instead of the
straightedge.
5.1.29 Removing Leg-waste
Figure 5.19 Legs screwed into housings
Figure 5.19: Now ready for assembly, the legs are fitted
and screwed or nailed into the housings, making sure
that the lower lip of the birdsmouth cut fits tightly to
the underside of the stool top.
5.1.27 Fixing the Cleats
Figure 5.20: Next, the top edges of the cleats are
planed off to a 4 in 1 angle, to fit the underside of the
Figure 5.22: Finally, lay the stool on its alternate sides,
and alternately end for end, up against a wall, bench,
etc., and carefully cut off the waste from the legs with
a panel or hardpoint saw. Clean off waste material
from the sides of cleats and clean off any splintering
arrises to finish.
Figure 5.23: If it is discovered that the stool is
uneven and wobbly, turn it upside down and, as illustrated, place winding sticks (true and parallel miniature
straightedges for checking twisted material) on the
feet at each end and sight across for alignment. If in
line, then the floor is uneven; if out of true, plane
fractions off the two high legs and re-sight and
re-plane, if necessary, until the legs are even.
Nail Boxes
53
Remove ears
∗ Mark leg-arris
564
length (564 mm)
down each leg
∗
Figure 5.21 Join ‘lal’ marks with
straightedge (or use template or bevel) to
establish line of feet
Join ‘lal’ marks with straightedge
Stool-top length +100 mm each end
95
75
Figure 5.22 Lay the stool on its side, end against the
wall, and remove leg-waste
Uneven legs
34
60
Figure 5.24 Optional vee-ended top
Alternatively, as illustrated, a separate vee-ended
board, of ex. 25 mm material, can easily be made and
fitted to the top of the stool – and removed again,
when required.
Figure 5.23 Using winding sticks on uneven legs
5.1.30 Vee-ended Top
Figure 5.24: Sometimes, a vee-shape is cut in the end
of a stool to facilitate the holding of doors-on-edge
when they are being ‘shot-in’ (planed to fit a
door-opening). To accommodate this, the legs ought
to be set in 150 mm from each end of the stool top,
instead of 100 mm.
This allows the top of the stool to touch the wall at
one end, while the other holds the door in the vee cut
without touching the bottom of the cleat. However,
this does create a potentially dangerous stool if used as
a ‘hop-up’, and you step along the stool towards an
over-extended end.
5.2 NAIL BOXES
5.2.1 Introduction
Nail boxes appear in all shapes and sizes and vary
between very simple – and often very rough – constructions where all joints are butted and nailed, to
more elaborate forms with dovetailed corners, housed
cross-divisions and shaped handles.
5.2.2 Preferred Nail Box
The dovetailed type are not now seen in industry, but
serve as a very useful jointing exercise for apprentices,
trainees or students and can also provide a presentable
nail box for one’s own workshop. Apart from this, the
54
Making Builder’s Plant for Site Use
300
120
simple, easier-constructed box serves its purpose well
enough – whether in the workshop or out on site.
This purpose is to provide a manageable means of
transporting a sufficient supply of nails of different
size and type from one work-location to another.
5.2.3 Compartment Variations
Generally speaking, on first-fixing operations, the
compartments in the box can be fewer and therefore
larger, to house such nail sizes as 75 and 100 mm
round-head wire nails, whereas, on second-fixing
operations, more compartments are usually needed to
house a greater variety of smaller nails such as 38 and
50 mm oval nails, etc.
0
25
0
45
Figure 5.26 Modern nail box
70
5.2.4 Dovetailed Nail Box
130 mm
0
45
25
0
the box, without side housings, and fixed through the
sides and ends with 38 mm oval or wire nails. Finally,
the handle is inserted and nailed or screwed through
the top of each end – after making two pilot holes.
5.3 HOP-UPS
5.3.1 Introduction
Figure 5.25 Dovetailed nail box
Figure 5.25: The one illustrated is built up of
70 ⫻ 12 mm finish sides and ends, jointed together
with through-dovetails on each corner. It has a
145 ⫻ 21 mm finish handle-division housed into the
ends, to one-third the end-material thickness, and solid
timber or 6 mm plywood cross-divisions housed 4 mm
into the sides and handle division. The 130 ⫻ 32 mm
slot for the handle is drilled out with a 32 mm diameter centre bit, chisel-pared and chamfered to a clean
finish. The assembly is then glued together and checked
for squareness before the 4 mm plywood base is glued
and pinned (with 15–18 mm panel pins) into position.
5.2.5 Modern Nail Box
Figure 5.26: As illustrated, this is built up of 10–12 mm
plywood sides, ends and cross-divisions, an ex.
50 ⫻ 25 mm handle morticed into each end, and a 4 or
6 mm plywood base. The assembly is nailed together
unglued with 38 or 50 mm round-head wire nails. The
cross-halved plywood divider is dropped loosely into
Even though ‘wet plastering’ has diminished since
dry lining became popular, hop-ups are still of use
when rendering/floating and setting walls. In these
situations, the plasterer uses a floating or skimming
trowel, a handboard (hawk) with which to repeatedly
carry the plaster to the wall, and a ‘board and stand’
from which to feed the material onto the hawk.
Because the loaded hawk is in one hand and the
trowel in the other, he cannot easily – or safely – climb
step-ladders if plastering to a height beyond his reach.
Furthermore, step-ladders inhibit the plastering
action. So, there is a need for an easily movable (repositioned by foot), easily ascendable (stair-like rise), and
non-restrictive piece of equipment such as a hop-up.
5.3.2 Traditional Hop-up No.1
Figure 5.27: As illustrated, this is simple in design and
structure, built up of square-edged or tongued-andgrooved boarding, cleated and clench-nailed (protruding nail-points bent over for a stronger fixing). The
100 ⫻ 25 mm sawn boarding, shown here, is arranged
to form a two-step hop-up with a step rise of 225 mm.
First, two side-frames are constructed of vertical
board and horizontal cleats clench-nailed together
Board and Stand
55
hop-up of this width (600 mm) 18 mm plywood or
MDF board could also be used as tread boards.
0
225
60
5.4 BOARD AND STAND
20
0
5.4.1 Introduction
225
A board and stand is also a piece of site equipment
still required in a wet-plastering operation. It acts as a
platform upon which the mixed plastering materials
are deposited and are more easily trowel-fed onto the
hawk placed under the board’s edge. There are two
types of stand that can be made, one being rigid in
construction, the other, folding. Both types have a
similar, separate mortar board which lays in position
on top without any attachment to the stand.
Figure 5.27 Traditional hop-up No.1
5.4.2 Rigid Stand
with 56 mm round-head wire nails or cut, clasp nails.
These frames are then joined together by the tread
boards being nailed into position and two cross-rails
at low level, one at the front, the other at the back.
These should be fixed with 63 mm round-head wire
nails or oval nails. Finally, a diagonal brace of 50 ⫻ 25
or 75 ⫻ 25 mm section is also fixed at the back.
Figure 5.29: The height of this can vary from 675 to
750 mm and the width and depth is usually about
600 ⫻ 600 mm. This allows the board to overhang the
stand to facilitate the loading of the hawk. The material used can be sawn or prepared softwood. First,
Rigid stand
600
5.3.3 Traditional Hop-up No.2
0
60
Figure 5.28: The hop-up shown here is simplified by
using 18 mm plywood or Sterling board as side frames,
boarded steps, cross-rails and diagonal bracing. On a
675 to 750
50 ⫻ 50
20
200
0
75 ⫻ 25
900
200
Mortar board
0
20
0
0
60
50
0
20
Figure 5.28 Traditional hop-up No.2
Figure 5.29 Plasterer’s stand and board
56
Making Builder’s Plant for Site Use
50 ⫻ 50 mm legs and 75 ⫻ 25 mm rails are cut to
length to form two frames. On each frame, one rail is
nailed to the top of the legs, the other is nailed about
100 mm clear of the bottom. Each frame is then
braced diagonally with 50 ⫻ 25 mm or 75 ⫻ 25 mm
bracing material and the two frames joined with the
remaining cross-rails at top and bottom. Finally, the
two remaining braces are fixed; 50–63 mm roundhead nails are used throughout.
5.4.3 Folding Stand
900
18 mm plywood
mortar board
15
interlocking frames. The inner frame must be minus a
tolerance allowance in width to enable it to fit easily
into the outer frame. Ideally, the allowance, say
2–3 mm, should, on assembly, be taken up with a
washer each side, between the frames.
Once the frames are bolted together, they are partly
retained in the open position by the middle rails on
each side, but mostly rely on the top rails fitting
between the cleats of the mortar board. Accordingly,
the cleats on the board must be so positioned as to
leave a clear middle area of 600 mm. Before bolting
the frames together, diagonal braces should be added
for extra strength as indicated. Nails or screws can be
used for fixing the rails and braces, although with this
type of construction screws are advisable. Finally, the
ends of the bolts, if protruding more than a reasonable
amount, should be close-cut and burred over.
5.4.4 Mortar Boards
0
60
0
15
0
0
675 to 750
60
60
0
63 ⫻ 38
75 ⫻ 25
These can be made from 900 mm to 1 m square, either
from tongued-and-grooved boarding, cleated and
clench-nailed together or from sheet materials such as
resin-bonded plywood, MDF board, Sterling board or
similar. As indicated, the sharp corners are usually
removed. Whether made from sheet material or T&G
boards, cleats, as indicated, will still be required to
retain the board’s position on the stand. Cleat material
is usually 75 or 100 ⫻ 25 mm. Mortar boards used by
bricklayers – often referred to as spot boards – only vary
by their size, which is usually between 600 and
760 mm square.
5.5 BUILDER’S SQUARE
Figure 5.30 Folding stand
Figure 5.30: When in the open position, the height,
width and depth can be similar to those given for the
rigid stand. The leg-length can be worked out as
already explained for the saw stool, either by practical
geometry or by calculation (by using, say, 750 mm as
vertical height and 600 mm as base measurement and
adding at least 70 mm allowance for splay cuts).
Alternatively, the side elevation showing the crossed
legs could easily and quickly be set out at half-scale or
full-size, so that the exact details of legs were available.
Construction Details
The legs, of 63 ⫻ 38 mm or similar section, with central holes drilled for 9–12 mm diameter coach bolts,
are fixed together with 75 ⫻ 25 mm rails to form two
5.5.1 Introduction
Figure 5.31: Builders’ squares are large wooden trysquares, made by the carpenter or joiner, for use on
site during the early stages of setting out walls and
foundations, etc. Their size varies from about 1 to 2 m
and the two blades, forming the square, may be of
equal length or have one blade longer than the other.
They are used mostly by bricklayers as an aligning tool
rather than an instrument, to help establish internal
right-angles of walls or partitions. The initial setting-out
of right-angled walls nowadays is usually done with an
instrument such as an optical site square.
5.5.2 Material and Construction
Details
The material, from ex. 75 ⫻ 25 mm for the smaller
size, up to ex. 125 ⫻ 32 mm for the larger squares,
Builder’s Square
57
This measurement ⫼ 2 = inaccuracy
Testing the square
for squareness
2. Reverse and mark rightangle in second position:
check discrepancies as above
1. Mark right-angle in
first position
Straightedge laid on flat surface
Plan view
Shoulder length
divided by 5
1m
SL
—
5
ex. 75 ⫻ 25
1m
should be prepared softwood, carefully selected for
density, straight grain and freedom from large knots.
A corner half-lap joint is used on the connection of
the two blades and should be screwed together.
Alternatively, this joint can be formed with a
haunched mortice and tenon. Single-splay dovetail
halving joints, as illustrated, are used to connect the
diagonal brace to the blades – and these should also be
screwed; joints are not usually glued.
5.5.3 Assembling the Square
First, make the right-angled corner joint and fix the
two blades together temporarily with one screw. Now
test for squareness with either a roofing square or by
Figure 5.31 Builder’s square
using what is known as the 3–4–5 method. This refers
to a ratio of units conforming to Pythagoras’ theorem
of the square on the hypotenuse being equal to the
sum of the squares on the other two sides. For
example, using 300 mm as a unit, mark three units
(3 ⫻ 300 ⫽ 900 mm) accurately along one face-side
edge from the corner, four units (4 ⫻ 300 ⫽ 1.2 m)
along the adjacent edge from the corner and then
check that the diagonal measures five units
(5 ⫻ 300 ⫽ 1.5 m). Adjust the blades, if necessary,
until the diagonal measures exactly five units. Lay the
brace carefully into position and mark for halving
joints. Now dismantle the corner joint, form the other
two joints, then reassemble, screw up and test for
squareness.
58
Making Builder’s Plant for Site Use
5.5.4 Testing for Squareness
Figure 5.31: As illustrated, this can be done by laying a
straightedge on a flat surface such as a sheet of plywood or hardboard, squaring a mark from this with
the builder’s square in a left-hand position, reversing
the square to a right-hand position and marking
another line close to the first – then checking for any
discrepancies in the lines. If necessary, true up any
small inaccuracies by planing.
5.6 STRAIGHTEDGES AND
CONCRETE-LEVELLING BOARDS
5.6.1 Straightedges
Figure 5.32: These are boards used by various tradespeople for setting out straight lines, checking surfaces
for straightness, and levelling and plumbing with the
addition of a spirit level. As the name implies, the
ex. 100 ⫻ 25 mm to ex. 150 ⫻ 2 5 mm
Small straightedges about 1 to 2 m long
ex. 200 ⫻ 32 mm
to
ex. 225 ⫻ 38 mm
Large straightedges about 3 m or more
Figure 5.32 Straightedges
essential feature of these boards is that the two edges
are straight and parallel to each other. This can, of
course, be done by hand-planing, but is best achieved
on surface planer and thicknessing machines.
Varying Sizes
Lengths of straightedges vary from 1 to 2 m, with sectional sizes of ex. 100 ⫻ 25 mm to ex. 150 ⫻ 25 mm.
Large straightedges of 3 m or more in length, are usually made from ex. 200 ⫻ 32 mm, or 225 ⫻ 38 mm
boards. Holes of about 38 mm diameter were traditionally drilled through the straightedge, at about
900 mm centres along its axis. This was done to establish the board visually as a proper straightedge and to
discourage anybody on site from claiming it for other
uses. Prepared softwood, of similar quality to that
selected for the ‘building square’, should be used.
Periodic checks for straightness are advisable.
5.6.2 Concrete-levelling Boards
Figure 5.33: These are usually about 5–6 m long, made
from 225 ⫻ 38 mm sawn softwood. As illustrated, a
handle arrangement is formed at each end to assist in
easier control and movement of the board during the
levelling operation. If a bay of concrete was to be laid
within a side-shuttered area, or within the confines of
a brick upstand, the levelling board would have to be
long enough to rest on the shutters or brickwork each
side. As the concrete was being placed, a person at
each handle would tamp the concrete and pull the
board, zig-zagging back and forth across the surface.
760
Handle attachments each end
225 ⫻ 38 mm Levelling board
About 5 to 6 m long
ex. 50 ⫻ 25 mm
handle
50 mm Ø ‘Bulldog’
connectors bolted
between timbers
225 ⫻ 38 mm
75 ⫻ 38 mm
laminated
timbers
12 mm Ø bolt and
50 mm Ø ‘Bulldog’
timber connectors
Figure 5.33 Concrete-levelling
boards
Plumb Rules
5.7 PLUMB RULES
5.7.1 Traditional Plumb Rule
5.7.2 Modern Plumb Rule
Figure 5.35: Although extra-long spirit levels are now
obtainable to replace plumb rules, the modern plumb
rule consists of a straightedge of about 1.675 m length
of ex. 125 ⫻ 25 mm selected softwood, with a shorter
(say 750 mm) spirit level placed on its edge when in
use. When fixing door linings, or striving for accuracy
in plumbing on any similar operation, the straightedge
and level combined are preferable to the relatively short
spirit level on its own. This is because any inaccuracies
in the shape of hollows or rounds in the surface of the
item being plumbed/fixed, show up easily because of
the plumb rule or straightedge’s greater length.
SPIRIT
LEVEL
Figure 5.34: This traditional piece of equipment, in its
original form as illustrated, is here for reference, as it
is obsolete nowadays, even though plumb bobs themselves are still very useful in some carpentry operations. When used with a plumb rule, waiting for the
plumb bob to settle against the gauge line, to indicate
plumbness, was a tedious and slow operation –
although very accurate, if carefully done.
Plumb
bobs
Figure 5.34 Traditional plumb rule and plumb bobs
59
Figure 5.35 Modern plumb rule
6
Fixing Door Frames,
Linings and Doorsets
6.1 INTRODUCTION
Wooden frames and linings are fixed within openings
to accommodate doors which are to be hung at a later
stage in the second-fixing operation. This is necessary
where wet trades, such as bricklaying and plastering and
early-stage rough building operations, are involved.
However, where dry methods of construction are used
(or achieved, as described later), doorsets are sometimes
used. These are made up of linings or frames with prehung doors attached, locks or latches and architraves
in position. This reduces site work by eliminating the
conventional second-fixing door-hanging operation.
6.1.1 Lining Definition
Figure 6.1: A door lining, by definition, should completely cover the reveals (sides) and soffit (underside of
the lintel) of an opening, as well as support and house
the door. Nowadays, this coverage only usually occurs
where the opening is within a block or stud-partition
wall.
6.1.2 Frame Definition
Figure 6.2: A door frame should be of sturdier construction, strong enough to support and house the
door without relying completely on the fixings to the
structural opening. Unlike linings, which have loose
doorstops, frames are rebated to receive the door and
usually have hardwood sills.
6.1.3 Internal or External
Figure 6.1 Door lining
Generally speaking, frames are used for external
entrance doors and linings for internal doors. Apart
from this, door frames are usually set up and built in
at the time the opening is being formed, whereas a
lining, because of its thinness (usually 21–28 mm) and
flexibility, should only be fixed after the opening is
formed. Linings also require a greater number of
fixings and a more involved fixing technique than
door frames, as described later.
Introduction
Frame
jamb
61
Lining
leg
Door stop
Plasterer’s rule
Figure 6.4 Protection strips
future risk of decay, built-in frames should be treated
with preservative before being fixed, preferably at the
manufacturing stage. Usually, at the time of being
built in, the abutment-surfaces of the frame have a
continuous strip of damp-proof material such as bituminous felt, plastic film (to BS 743) or waterproof
building paper fixed to the full width, as in Figure
6.3(a), or fixed to the inner edges, as in (b) and (c).
This shows the use of plastic film fixed to framejambs and sandwiched between brickwork and blockwork to stop any moisture in the outer wall from
bridging the cavity.
6.1.5 Protection strips
Figure 6.4: The inner edges of the jambs (sides) of
frames and the legs (sides) of linings, especially at low
level, should be protected from wheelbarrow damage
and other careless movement of material and plant, by
being covered with temporary wooden strips. These
can be of whatever size; the illustration shows
38 ⫻ 12 mm strips fixed lightly with 38 mm oval nails
to face and edges of the jambs and legs. Of course, the
strips fixed to the edges would have to be removed if a
wet plastering operation were to take place, as
opposed to modern dry lining. This, as shown, would
allow the plasterer’s rule (straightedge) access to a
guiding edge.
Figure 6.2 Door frame
6.1.6 Setting up the Frame
(a)
(b)
(c)
Figure 6.3 Frame protection material applied (a) full
width (b) and (c) to inner edges and cavity
6.1.4 Protecting External Frames
Figure 6.3: To inhibit initial moisture penetration
into the timber from wet trades and to offset any
Figure 6.5: Built-in door frames are set up immediately before starting to build the walls, or sometimes
after the first brick-course has been laid. The position
of each door-opening reveal is set out and the frame is
stood up in position with one or two scaffold boards
supporting it at the head. Two boards (or two nails in
one board) are better, especially if the frame is twisted.
A 75 mm wire nail driven through the top of the
board(s) holds the frame. The nail is driven through
before lifting the board into position and the nailpoint rests on the frame – it is not driven in.
62
Fixing Door Frames, Linings and Doorsets
6.2 FIXING DOOR FRAMES
6.2.1 First Set
Frame
Sand
or
cement
Scaffold board
Alternative base and
head support
Bricks at
base
Packing
(a) Frame-cramp lug recessed ideally in grooved jambs
Figure 6.5 Setting up the frame
Scaffold
board
support
Safe-nailing
Alternatively, as illustrated, the nail is only driven into
the board – not through it – and the head of the nail
is used to hold the frame. This is quite effective and a
much safer practice if removal of the nail is eventually
neglected.
The jambs are plumbed by spirit level, then bricks
or blocks (or any heavy material) are piled at the foot
of the scaffold boards to hold them in position. The
head of the door frame must be checked for level and
adjusted if necessary.
3
6.1.7 Vertical Adjustments
2
Sill
Screed or
floor level
Temporary packing, if required
1
Figure 6.6 Vertical adjustments
Figure 6.6: These adjustments, under the sill, must
also take into account the eventual finished floor level
(ffl). It is also important to ensure that the head of the
frame meets brick courses. If the brickwork is flush or
slightly higher than the top of the frame, this will suit
the seating of the open-back or classic profile shape
cavity lintel. Any slight gap between frame-head and
the underside of the lintel will eventually be sealed
when the jambs and head are gunned around with a
flexible frame sealant.
(b) Check frame for plumb with spirit level
(c) Galvanized steel frame cramp
Figure 6.7 Fixing ties
Fixing Door Frames
63
Owlett’s Zinc-plated Screw Tie
(d) Owlett's zinc-plated screw tie
Figure 6.7(d): These also provide good fixings and are
screwed to the frame without vibration from hammering. They do not require screws, bradawl or screwdriver and can be offset or skewed to avoid the cavities
in hollow blocks. On the debit side, the brickwork or
block-work has to be stopped one course below the
required fixing to allow rotation of the loop when
screwing in, then the brick or block beneath the tie is
bedded – with some difficulty and loss of normal
bedding-adhesion.
Sherardized Holdfast
(e) Sherardized Holdfast
Figure 6.7 (continued) Fixing ties
Figure 6.7: As the brickwork or blockwork proceeds,
metal ties are usually fixed to the jambs and built into
the bed joints of the mortar. The first set of ties (one
to each jamb) must be fixed at low level, on the first
course of blockwork, or on the second or third course
of brickwork – no higher (Figure 6.7(a)).
6.2.2 Second and Third Sets
Figure 6.7(b): As the work progresses, the frame must
be checked for plumbness from time to time in case
the supporting scaffold boards have been accidentally
knocked. At least two more sets of ties are fixed, at
middle and near-top positions. For storey-height
frames (from floor to ceiling, with fixed glass or fanlight above the door opening), a total of four sets of
ties is advisable.
Different types of tie are available, each with points
for and points against, as listed below.
Figure 6.7(e): Holdfasts are fixed quickly and easily,
being driven in by hammer. The spiked ends spread
outwards when driven into the wood, forming a
fishtail with good holding power. The main disadvantage is that the hammering disturbs the frame and
permanently loosens any Holdfasts already positioned
in the still-green (unset) mortar.
Marking the Positions
Whatever type of frame cramps or ties are used, their
intended positions, relative approximately to bed-joints,
are best boldly marked on the jambs with a soft pencil
(as seen at points (1), (2) and (3) of Figure 6.7(b)), to
act as a reminder to the bricklayer as the work rises.
Braces and Stretcher
762
100
Brace
Stretcher
(a)
(b) Gaps at sides of cramps
causes lateral looseness
of frame
Galvanized Steel Frame Cramp
Figure 6.7(c): These provide good fixings and, because
they are screwed to the frame, any cramps (or ties)
already fixed and bedded in mortar are not disturbed
by hammering. Also, by resting on the last-laid brick,
the next brick above the tie is easily bedded. The disadvantages are: handling small screws; requiring a
screwdriver and bradawl (especially if no carpenters
are on site yet, or they are sub-contract labour, not
wanting to be involved); if no groove is in the frame,
the upturned end of the cramp inhibits the next brick
from touching the frame; doubts as to whether rustproofed screws were used.
Figure 6.8 (a) Braces and stretcher; (b) effect of early
removal
Figure 6.8: Usually, one or two strips of sawn timber,
of about 50 ⫻ 18 mm section, acting as temporary
diagonal corner braces, are nailed lightly to the frame
to keep it square at the head. Another piece, called a
stretcher, is fixed near the bottom to keep the jambs
set apart at the correct width. Ready-made frames
delivered to the site, already have braces and a
stretcher – or a sill.
64
Fixing Door Frames, Linings and Doorsets
Early Removal
Weatherboard
Figure 6.8(b): Although there is good reason on site to
remove the braces and stretcher at the outset, because
they obstruct easy passage through the opening, they
should not be knocked or removed until the surrounding brickwork or blockwork is set. The illustration
shows gaps at the sides of a frame cramp which will
cause lateral looseness of the frame. This is due to the
frame being accidentally knocked or the braces and/or
the stretcher being removed (knocked off ) too early,
before the mortar was set.
Door
Mastic
joint
ffl
Step
Sill
(a)
6.2.3 Alternative Fixing Method
Door
Figure 6.9 Frame-fix screw
Carpet
Figure 6.9: A popular practice used nowadays for
fixing door frames is to position and build them in
without any fixings, care being taken with level and
plumbness – especially lateral plumbness, affecting
the brick reveals. Eventually, when the brickwork
is completed and set, the frame is checked for plumbness on its face edges, minor adjustments made,
then drilling and fixing to the brick reveals is
carried out with nylon-sleeved Frame-fix or Hammerfix screws. At this stage, rather than risk the quality
of the fixing in the recently set mortar joints, more
reliable fixings will be achieved by drilling into the
bricks.
6.3 FRAME DETAIL
6.3.1 Weathering the Sill
Figure 6.10(a): For purposes of weathering and
structural transition between exterior and interior
levels and finish, external door frames usually have
hardwood sills – sometimes referred to as thresholds.
Traditionally, water bars, with a sectional size of
25 ⫻ 6 mm, ran along a groove in the top of the
sill, protruding 12 mm to form a water check/draught
excluder. These bars were made of brass or galvanized
steel, but when this form of weathering is used
nowadays, the bar is available in grey nylon or browncoloured rigid plastic with a flexible face-side strip
which acts as a draught seal against the rebated edge
of the door. In this arrangement, a weatherboard must
be fitted to the bottom face of the door.
(b)
Figure 6.10 (a) Traditional sill with water bar;
(b) weather seal
6.3.2 Modern Weathering Method
Figure 6.10(b): There are now very effective weather
seals available for fixing to the threshold or sill of
exterior frames. The wooden sill does not require the
groove for a water bar, as before, but if a groove is
present, it should be filled with a frame-sealant compound. These weather seals/draught excluders, resembling an open channel, are usually made of extruded
aluminium in natural colour or with a brass effect
finish.
Fitting and Fixing
When being fitted, the weather-seal channel is
simply cut to length, fitted with rubber seals to the
manufacturer’s instructions and screwed in position to
the sill or threshold. The door usually has to be
reduced by about 25 mm at the bottom and the metal
channel may require to be sealed at each end with silicone or a frame-sealant compound. This prevents
moisture seepage from the channel and possible wet
Fixing Door Linings
rot to frame or sill. Any rainwater that does enter the
channel should drain out to the exterior, via weep
holes in the inside front-edge of the channel.
6.3.2 Anchorage of Jambs
65
internal types may have separate door stops fixed to the
jambs and underside of the head to form a rebate
(Figure 6.12(b)). The former are referred to as sunken or
stuck rebates and the latter as loose or planted door stops.
6.3.4 Door-frame Joints
Jambs
(a)
(b)
Figure 6.11 Anchorage of jambs; (a) double tenon;
(b) dowel
Figure 6.11: Sills also provide excellent anchorage for
the feet of the jambs which are double-tenoned into
them with comb joints (Figure 6.11(a)). Although
usually through-jointed, the softwood jambs would
be better protected if only stub-jointed into the
hardwood sill. If the frame is of the type without a
sill, 12 or 18 mm diameter metal dowels can be
used to secure the jambs (Figure 6.11(b)). A hole
is drilled up into the foot of each jamb with an
electric or cordless drill and a combination auger bit,
or with a brace and a Jennings’ twist bit, and the
dowels are hammered in to leave a 40–50 mm protrusion. When the frame is being set up, the protruding
dowels are either set into dowel holes or they are bedded in concrete or sand-and-cement floor screed, etc.
Galvanized steel pipe, of a suitable diameter, can also
be used for dowels.
6.3.3 Sunken Rebates or Planted
Stops
(a)
(b)
Figure 6.12 Rebates and stops
Figure 6.12: External frames should be rebated from
solid wood to house the door (Figure 6: 12(a)), but
Figure 6.13 Door frame joints
Figure 6.13: Traditionally (Figure 6.13(a)), mortice
and tenon joints were used to join the jambs to the
head and sill. Projections of the head and sill, called
horns, were left on to strengthen the joint and to
anchor the frame when built into the brickwork.
However, horns do not lend themselves so well to
cavity-wall construction and bricklayers tend to cut
them off anyway. In line with this practice (Figure
6.13(b)), the jambs of frames are now comb-jointed to
the head and sill and pinned through the face, producing strong corner joints without the need for horns.
6.4 FIXING DOOR LININGS
6.4.1 Choice of Fixings
Linings may be fixed to timber stud partitions with
75 mm oval nails, brad-head or lost-head type or, traditionally, with cut clasp nails – which, when punched
in, leave a larger hole to fill, but provide a really secure
fixing. Alternatively, linings may be counterbored,
screwed and pelleted. Screwing and pelleting is usually
restricted to the fixing of hardwood linings, but can be
justified on good-quality softwood jobs.
6.4.2 Fixing Problems
Although cut clasp nails may also be used when fixing
to medium-density partition blocks, other aerated
building blocks do not hold these fixings very well.
Therefore, when fixing linings to walls such as this, it
is better to use mid-width positioned through fixings
(drilled and fixed through timber and wall in one
operation), such as nylon-sleeved Frame-fix screws.
66
Fixing Door Frames, Linings and Doorsets
6.4.3 Screwing and Pelleting
Figure 6.14(a)–(f ) outlines the various steps involved
with screwing and pelleting in relation to the following points:
(a) lining counterbored at the selected fixing points
on each leg with a 12 mm diameter centre or
twist bit, about 9 mm deep;
Shankhole drilled
to suit screw
(a)
(b)
(c)
(d)
Lining counterbored
(g)
Machine-made pellets
(e)
Spirit
level
check
Datum line ∗
Remove
door
stops
(f)
(b) shankholes drilled to suit gauge of screw;
(c) lining screwed into position, taking care not to
damage the edges of the counterbored holes wih
the revolving blade of the screwdriver;
(d) pellets then glued, entered lightly into holes,
lined up with the grain direction and driven in
carefully;
(e) bulk of pellet-surplus removed with chisel;
Packing
to unfixed
leg
(n) Pinch-rod in bottom position
Packing
∗
900
(h) + (i)
ffl
(j)
∗Equal projections
each side for
plaster
Packing
(k)
Double fixings with
cut, clasp nails
Fixings with Framefix screws
(o) Eyeing angle for alignment of legs
Plumb rule
Packing
Lintel
Straightedge
(p) Packing to lining head
(l) Plumbing and checking squareness at base of legs
Pencil
Stretcher
(m) Marking stretcher to make pinch-rod
Figure 6.14 Fixing door linings
Packing
Fixing Door Linings
(f ) remaining pellet-surplus cleaned off with a block
plane or smoothing plane.
6.4.4 Fixing Technique
Owing to a lining’s relative thinness and flexibility, the
fixing operation can be problematic and unmanageable unless a set procedure is adopted. The following
fixing technique, illustrated by Figures 6.14(g)–(p), is
therefore recommended.
First Steps
(g) First remove the door stops which are usually
nailed lightly in an approximate position on the
lining legs and set aside.
(h) If working on unfinished concrete floors, check
the finished floor level (ffl) in relation to the base
of the lining. As illustrated, this is best done by
measuring down from a predetermined datum
line set at 900 mm or 1 m above ffl. Place packing
pieces under the lining’s legs, as necessary.
Wedging and Packing
(i) Stabilize the lining in an approximate position by
placing small wedges temporarily above each leg,
in the gap between lintel and lining-head, then
check the head with a spirit level and adjust at
the base, if necessary. If gaps exist between the
structural opening and the back of the lining’s
legs, as is usual, pack these out with plastic shims,
obtainable in varying colour-coded thicknesses,
or with pieces of non-splitting material such as
hardboard or plywood, initially on each side of
the top fixing positions only.
Adjusting and Initial Fixing
(j) Adjust the top of the lining to establish equal
projections on each side of the opening for eventual plaster-thickness on the wall surfaces, or to
form equal abutments for the edges of dry-lining
boards.
(k) Now fix the lining near the top, through the packings on each leg, either with two nails per fixing
or with mid-width screw fixings.
Plumbing, Squaring and Fixing
(l) Now plumb the lining on the face sides and edges
with a long (1.8 m) spirit level, or alternatively, a
1.8 m straightedge with a short spirit level placed
on it. Pack the bottom position each side as
required and fix through one packing only. Check
for squareness of the fixed leg at the base with a
straightedge and try-square, as illustrated, then
pack and complete the intermediate fixings on
67
the same leg, checking before and after each
fixing with the long level or straightedge. The
amount of fixing points on each side should ideally
be five, but not less then four. These should be
placed at about 100 mm from the underside of
the head, 100 mm from the ffl, and two or three
intermediate points on each side.
Converting Stretcher to Pinch Rod
(m) Next, remove the stretcher from its position at
the base of the lining, denail it, hold it up to a
position just below the lining head, mark exact
inside lining-width and cut to make a pinch rod.
(n) Fit the pinch rod in the bottom section of the
lining-legs, as shown, and pack accordingly
behind the lower fixing point on the
unfixed leg.
Checking, Aligning and Final Fixing
(o) Check the plumbness of the unfixed leg for correct sideways position and check the alignment
by sighting across the face edges as illustrated.
Now fix the bottom, then the intermediate
points, moving the pinch rod to each fixing area
and packing out, if necessary, before fixing. The
lining head is not normally fixed to the lintel
unless the opening exceeds the normal width.
Packing to Lining Head
(p) However, the head does require to be held firmly
by replacing the initial temporary wedges mentioned in point (i) with packing or plastic shims
driven into the gap between the lintel and head,
at the two extremes only, immediately above each
leg. Failure to complete this detail can result in
the head becoming partially disjointed from the
legs, at the tongued-housing joint, when final
nailing of the head door-stop is completed at a
later stage.
Finishing Touches
Remove the corner brace or braces (although this
could have been done earlier, after points (g) or (h) to
facilitate easier working). If nailed, punch in all nail
fixings to about 3 mm below the surface. If screwed
with nylon-sleeved Frame-fix screws, check that these
are at least flush or slightly below the surface (having
been fixed in the mid-width area, they should be covered by the door stops). Or, if counterbored for pellets,
complete the pelleting operation as outlined in points
(d) to (f ). Finally, replace the door stops in their temporary position and fix protection strips, if considered
necessary, as mentioned earlier in the text relating to
Figure 6.4.
68
Fixing Door Frames, Linings and Doorsets
6.5 SETTING UP INTERNAL
FRAMES PRIOR TO BUILDING
BLOCK-PARTITIONS
6.5.1 Introduction
In these situations, the first step is to set out the wall
positions on the concrete floor in accordance with the
architect’s drawing. Providing the structural walls are
square to each other, the various internal partitions
required need only be measured out at two extreme
points from any wall to form parallels and squares.
6.5.2 Spotting
Holding Frame at Foot
Figure 6.16(a): The first course of blocks can be laid and
when set will act as a means of steadying the feet in one
direction, while loose blocks on either side will hold the
position in the other direction. Alternatively, notched
pieces of wood can be placed against the feet or against
the protruding metal dowels on the opening side and
fixed to the concrete floor by means of a cartridge tool.
Holding the Frame at Head
Figure 6.16(b): The head of each frame can be held by
a leaning scaffold board or boards – but a far better
method is to use wall cleats and a system of top
braces. The braces, of say 50 ⫻ 18 mm sawn timber,
must be triangulated or placed in such a way as to create stability. The wall cleats, about 300 mm long, of
say 100 ⫻ 25 mm timber, can be fixed to the walls
with 75 mm cut clasp nails, with heads left protruding
for easy removal later. If these fixings are unsuitable
for the walls, masonry nails may do the job.
Figure 6.15 Spotting
Figure 6.15: This setting out is best done with a steel
tape rule and a method of marking known as spotting.
A spot of mortar (about half a trowelful) is placed in
position on the floor, then trowelled down to form a
thin slither. The tape rule, peferably being held at one
end, is pulled taut over the mortar spot and the troweltip is cut through it at the required measurement.
(a) Holding frame at foot
Top brace
Wall cleat
6.5.3 Use of Builder’s Square
Short-length offset walls can be set out by using a
builder’s square (a wooden square, the making of which
is covered in Chapter 5). Once the position of all the
walls is determined, the next step is to set out the
required door openings. Straightedges can be used to
join extreme marks and to allow further spots to be
placed at intermediate positions to indicate the openings.
(b) Holding frame at head
6.5.4 Positioning the Frame
Figure 16.6: The frames should be stood in position to
relate to the setting out – preferably when the mortar
spots are set – and some means of holding them at the
foot and head must be devised. The following optional
methods can be used.
(c) Isometric view of braced frame
Figure 6.16 Positioning the frame
Subframes
A
∗Heads
A
∗∗Transoms
∗
A
69
Top
hung
A
Bottom
hung
∗∗
(a)
(b)
(c)
(d)
(e)
Sections A–A
Figure 6.17 Storey frames
6.6 STOREY FRAMES
the wall is built, these edges should be covered with a
strip of expanded metal lath – unless dry-lining
methods are to be used.
6.6.1 Internal and External with
Fanlights
Figure 6.17: Storey frames may be internal or external
and, as the name implies, fully occupy the vertical
space between the floor and ceiling. The frame comprises two extended jambs, a head, a transom above
the door and, usually, a hardwood sill on external
types. The frame-space above the door can be (a)
directly glazed, (b) contain louvres, (c) house a fixed
sash, or (d) contain an opening sash (fanlight), opening outwards, or (e) inwards, for ventilation.
6.6.2 Extended Jambs Without
Fanlight
6.6.3 Fixing to Ceiling
Figures 6.18(b) and (c): When the ceiling above the
storey frame is timber-joisted, the extended jambs are
fixed to the sides of the joists or, more likely, to purposeplaced noggings between the joists. When the construction is of concrete, a timber batten or ground can
be ‘shot’ onto the ceiling with a cartridge fixing tool
and the jamb-ends fixed to this by (b) notching (cogging) or (c) butting and skew-nailing.
6.7 SUBFRAMES
Extended
jambs
(a) Subframes after
receiving linings
Door head
(a)
(b)
(c)
Figure 6.18 (a) Extended jambs without fanlight;
(b) jambs notched; (c) jambs butted
Figure 6.18(a): Another type of storey frame which
can be used on block partitions of less than 100 mm
thickness, would be minus the fanlight aperture, but
have extended jambs to allow for some form of fixing
to the ceiling. This would give greater rigidity to the
thinner wall whose strength might otherwise be
impaired by the introduction of an opening. The
jambs protruding above head level should be reduced
by the plaster thickness on each outer edge and, after
(b) Recessed frames used
as finished frames in
themselves
Figure 6.19 Subframes
Figure 6.19: If used, these can be recessed to take the
thickness of the blocks. The recess helps to stabilize
the block wall during construction and the subframe
is ideal in providing an eventual means of fixing the
lining and architraves – especially if these were in
hardwood. Sub-frames, if built in as illustrated, also
alleviate the fixing problems experienced with lightweight aerated block-work. When being built in, the
frames can receive metal ties or frame cramps as
normal and may be used as (a) subframes to receive
linings or (b) frames in themselves.
70
Fixing Door Frames, Linings and Doorsets
6.8 BUILT-UP LININGS
Rebate for doors
(b)
(a)
225
100
Rebate for doors
(b)
Figure 6.20 50 ⫻ 25 mm framed grounds for built-up
linings
Figure 6.20: Although built-up linings, covering the
full width of the reveals and soffit are not normally
used nowadays, the subject is mentioned here in case
it should be met on repair or conversion work. These
linings, labelled (a) on the figure, are built up on
grounds (b). Grounds are foundation battens which, if
set up accurately, packed and fixed properly in the
first-fixing operation, provide a good and true fixing
base for the separate parts of the lining and/or architraves in the second-fixing operation.
6.8.1 Framed Grounds
Figure 6.20: Framed grounds, illustrated at (b), consisting of two verticals and multi-spaced horizontal
members morticed and tenoned together, looking like
a ladder, were shop-made and fixed on site to suit
built-up linings. These linings, used on walls of
225 mm thickness and above, were so constructed to
minimize the effects of shrinkage across the face of
the wider timber. The fixing technique for the three
(two sides and a head) sections of framed grounds,
would be similar to that used in fixing linings.
6.8.2 Separate Architrave-grounds
Figure 6.21: Apart from the advantages of providing a
wider fixing area for architraves, these grounds also
protected lining-edges from becoming swollen by the
wet plastering operation. As illustrated, these grounds
were bevelled to retain the plaster on the outer edge.
Figure 6.21 Grounds for architraves
The width of the ground was such as to allow a minimum 6 mm overlap of the architrave on to the plaster
surface. Cut clasp nails, in sizes of 50, 63 and 75 mm,
were commonly used to fix the grounds to the mortar
joints of the wall.
6.9 MOISTURE EFFECT FROM
WET PLASTERING METHODS
Figure 6.22(a): When frames, linings or grounds
are set up and wet plastering methods are used, the
effect of this should be realized as it is often detrimental to the finished work. In the first instance,
excessive moisture from the wet rendering/floating
coat, labelled (1) in the figure, against the timber lining, causes the timber to swell (2). While still in this
state, the plasterer usually applies the setting/finishing
coat of plaster (3), flush to the swollen edges. The
timber eventually loses moisture and shrinks back to
near normal (4), leaving an awkward ridge between
the wall surface and lining (5), which upsets the seating of the architrave and the trueness of the mitres at
the head.
6.9.1 Solving the mitre problem
Figure 6.22(b)–(d): Geometrically, when architraves
are not seated properly, true mitre-cuts will appear to
be out of true, touching on the outer (acute) points
and open on the inner (obtuse) surfaces (Figure 6.22
(b)). If the plaster is only slightly proud of the lining
edges, sometimes it can be tapered off with a scraping
knife (or the edge of the claw hammer). This will seat
the architrave better, but minor adjustments to the
mitre-fit may still have to be made. If so, a sharp
smoothing plane or block plane is used. Figure 6.22(c)
shows how the problem can also be solved by trimming the plaster edges more drastically with a bolster
chisel, which is not ideal and involves making good, or
by rebating the edges of the architraves (Figure
6.22(d)).
Doorsets
Swollen edge (2)
Normal edge (4)
Setting coat (3)
Wet rendering (1)
71
two sets of architraves in position. These units are
supplied by specialist firms producing doorsets as a
factory operation. The main advantage of this modern
practice is a reduction in time-consuming site work by
eliminating conventional door-hanging, architrave and
lock-fitting and fixing.
Block
partition
Lintel
Awkward ridge left
after shrinkage (5)
(a) Moisture effect
10 mm gap
Gap
Architrave
Door
Threshold
Frame
Elevation
Figure 6.23 Vertical section through doorset
(b) Appearance of true-mitred architrave seated on raised
plaster edge
6.10.2 Suitability of doorsets
Plan
(c) Trimming plaster edges
Plan
(d) Rebating architrave edges
Because doorsets are complete units, they are not
immediately suitable where conventional methods
of construction, involving wet trades, are to be used.
The issues against this practice include the protrusion
of the architraves and hinges, which inhibits convential plastering methods, greater risk of damage to
doors, and possible distortion of door-jointing tolerances due to moisture absorption by the lining from
wet plaster.
6.10.3 Variations now Available
The possible variations now available are, therefore:
Figure 6.22 Moisture effects and their solution
6.10 DOORSETS
6.10.1 Introduction
Figure 6.23: Doorsets comprise linings or frames with
pre-hung doors attached, locks or latches and one or
1. fixing coventional linings in situations where ‘wet
trades’ are involved;
2. fixing conventional linings to openings in dry-lined
walls;
3. using doorsets and fixing to openings in dry-lined
walls; or
4. modifying the wet trade operation to enable
the use of doorsets to openings in plastered
walls.
72
Fixing Door Frames, Linings and Doorsets
6.10.4 Fixing Doorsets
Figure 6.24(a): The fixing of doorsets is somewhat
similar to the fixing technique already covered for
fixing conventional linings, except that doorsets are
usually fixed after the dry-lining operation has been
completed. This means that care must be taken
around the opening to ensure that the finished wall
thickness meets the exact width of the doorset lining.
One way of doing this, is to fix temporary profile
boards to the sides of the opening, similar to those
shown in Figure 6.24(b), as a guide for the dry-lining
fixer to work to. Other variations in technique include
using the pre-hung door to check door-jointing tolerances as final confirmation of level and plumbness
before completing the fixings.
6.10.5 Fixing Profiles
6.11 FIRE-RESISTING
DOORSETS
Figure 6.25: Doorsets with fire-resisting doors and
frames are available. If they have been tested to the
latest British Standards specification, instead of being
referred to as 1⁄2-hour and 1-hour firecheck doors and
frames, as in previous years, they should be referred to
as ‘fire-resisting doorsets’ with a quoted stability/
integrity rating. This rating is expressed in minutes,
such as 30/30 or 30/20, meaning 30 min stability/
20 min integrity. Stability refers to the point of collapse, when the doorset becomes ineffective as a barrier to fire spread. Integrity refers to holes or gaps
concealed in the construction when cold, or to cracks
and fissures that develop under test.
6.11.1 Frame and Door Details
Figures 6.24(b)–(d): The modification mentioned in
Section 6.10.3, variation 4, to enable the use of
doorsets to openings in plastered walls, involves producing plywood profiles of minimum 12 mm thickness, cut to the finished wall thickness and fixed
around the opening like a traditional lining. This can
be done either temporarily as a guide for the wet plaster (Figure 6.24(b)), to receive doorsets after removal
(Figure 6.24(c)), or permanently as an initial guide for
plaster and subsequent subframe for the doorset fixing
(Figure 6.24(d)).
Figure 6.25: As illustrated, fire-resisting doorsets are
identifiable by frames with sunken rebates of 25 mm
depth and varying thicknesses of door, according to
the amount of fire resistance required. Fire-resisting
doors are usually:
1. made up of solid-core timber construction, clad
with thin plywood, looking like thick blockboard;
2. built up of ply-clad framing with mineral infill; or
3. made up of timber frame, plasterboard, asbestos
fibreboard and bonded plywood facings.
100
Door
(a)
Plaster
5 mm
packing
Block
wall
(b)
Plywood
profile
(c)
(d)
Figure 6.24 (a) Horizontal section
through doorset within dry-lined wall;
(b) profiles ensure correct wall
thickness; (c) receipt of doorset after
profile removal; (d) act as subframe
for doorset
Fire-Resisting Doorsets
∗
60/60 FR
door
∗
30/30 FR
door
∗
46
82
35
30/30 FR
frame
56
92
60/60 FR
frame
25
35
25
45
45
∗ 10 ⫻ 2 mm grooves, housing intumescent
strips to jambs and head of frame
Figure 6.25 Fire-resisting
doorsets
6.11.2 Intumescent strips
As illustrated, the gaps (joints) between door and
frame usually contain intumescent strips which swell
up when heated, thereby sealing the top and side
edges of the door to increase the fire resistance.
Intumescent strips give a fairly good seal to hot
smoke, but as they do not become active until temperatures of 200–250⬚C are reached, they have no resistance to cold smoke.
6.11.3 Final Details
Figure 6.26: When fitting a fire-resisting doorset,
before fixing the second set of architraves, pack the
gaps between the frame and wall with mineral wool or
similar fire-resisting material.
The latest TRADA (Timber Research and
Development Association) Wood Information Sheet
on fire-resisting doorsets recommends that narrow –
not broadleaf – steel hinges should be used, to allow
continuous intumescent strip to jamb edges. Slim
locks, preferably painted with intumescent paint or
paste, should be fitted; the thickness and thermal mass
of these locks must be minimal. Over-morticing must
be avoided, otherwise these hidden gaps will, in effect,
reduce the integrity rating of the doorset.
Figure 6.26 Mineral wool packing to gaps of fireresisting frame
73
7
Fixing Wooden and
uPVC Windows
7.1 INTRODUCTION
An important consideration which determines the
method of fixing windows, is whether they are to be
built-in as the brickwork proceeds, or fixed afterwards
in the openings formed in the brickwork. This decision is related to the type of windows being installed
and whether they are robust enough to withstand
the ordeal of being used as profiles at the green
brickwork stage.
7.2 CASEMENT WINDOWS
7.2.1 Wooden Casement Windows
Figure 7.1 Built-in window frame
Figure 7.1: Casement windows made of wood are
usually built in as the brickwork proceeds. They are
secured with separate fixing devices, traditionally
referred to as frame cramps, which are covered in detail
in Chapter 6. Essentially, according to the type used,
they are either screwed or hammered into the wooden
side-jambs as the brickwork rises, to be built into the
bed joints. Two or three cramps each side is usual.
Like built-in door frames, these windows, after being
positioned, are plumbed and supported at the head
with one or two weighted scaffold boards pitched up
from the oversite or floor. If the windows have a separate sill of stone or pre-cast concrete, usually these
must be bedded first and protected with temporary
boards on their outer face sides and edges. Projecting
sills, formed with sloping bricks-on-edge, are usually
built at a later stage, the windows having been packed
up accordingly to allow for this.
7.2.2 uPVC Casement Windows
Windows made of uPVC are usually fixed after the
opening is formed, by screw fixings drilled through
the box-section jambs into the masonry reveal on each
side, or – if these fixings clash with the cavity seal – by
screwing into projecting side lugs which have been
pre-cut from multi-holed galvanized strap and
screwed to the sides of the window before insertion.
To allow for expansion and fitting, either the window
openings are built with a 6 mm tolerance added in
height and width, or the windows are ordered with a
6 mm tolerance deducted in height and width. In
either case, to ensure the correct size of opening is
built, temporary wooden profile frames made of
50 ⫻ 50 mm or 75 ⫻ 50 mm prepared softwood, with
6 mm WBP plywood corner plates, as illustrated, are
constructed and placed in position during the brickwork and blockwork operation.
Profile Frames
Figure 7.2: The temporary profile frames may be made
on site or in the workshop and can be removed soon
after the brickwork/blockwork has set, or left in position until the windows are to be installed. After careful removal, the frames may be dismantled, stored or
reused immediately. When the uPVC windows are
Glazing
75
Figure 7.3: If installing the double-glazed sealed
units into the fixed uPVC windows yourself – which is
easy enough once you know how – you must first
understand that the units must be seated on plastic
setting blocks and, if the window is an opening vent,
have plastic locating blocks in various positions on the
sides, as illustrated. Different thicknesses of plastic
blocks may be required, but they are normally 3 mm
thick, 25 mm long and should be as wide as the sealed
unit’s thickness (which is often 28 mm as standard
nowadays).
Figure 7.2 Temporary profile frame
7.3.2 Externally Beaded Glazing
eventually fitted, the expansion/fitting tolerance is
taken up equally all round – or as equally as possible –
with special plastic shims. On the sides of the window,
these shims, which are ‘U’ shaped, are slid around
each screw fixing before the screw is fully tightened.
Upon completion, or when all other building work
is complete, any projecting shim is trimmed off and
the gap around the window is gunned around with a
silicone sealant.
Internal Access
7.3 GLAZING
7.3.1 DIY Glazing
F
Fixed light
Top hung
Figure 7.4: With the setting and locating blocks fitted
snugly in position between the glass and the uPVC
casement, and the sealed unit pushed in to rest up
against the upstanding inner edge, the prefitted shuffle
beads, which were taken out to gain access for glazing,
are now pivoted into the small front lip and snapped
into position. Ideally, these should be pre-marked
L/H, R/H, TOP and BOT, so that they relocate in
their original positions.
L/H side hung
R/H side hung
Figure 7.3 Position of setting and location blocks
On the other side of the glass now, the unit is pushed
outwards, to be hard up against the external beads just
fitted. This creates a small gap between the glazed
unit and the grooved, upstanding edge of the window.
The so-called wedge gasket, illustrated in position in
Figure 7.4(a), is fed into this gap all round, forcing the
unit forward and locking and sealing the external
beading. The gasket, which has to be cut or partlysnipped on its concealed face at each corner (with at
least a 25 mm length-allowance added each time to
ensure a well-compacted fit), is not easy to push in. To
assist with the task, it would be advisable to make a
Sealed unit
Shuffle bead
40
Wedge gasket
150
4
Setting block
(a)
(b)
Figure 7.4 (a) Externally
beaded glazing; (b) caulking
tool
76
Fixing Wooden and uPVC Windows
simple wooden caulking tool (Figure 7.4(b)) and, if
still difficult, diluted washing-up liquid can be
brushed into the gap prior to inserting the gasket.
Sealed unit
Clip-in
bead
800 mm
Firtree
gasket
1500 mm
800 mm
7.3.3 Internally Beaded Glazing
(b)
FFL (finished floor level)
Setting
block
300 mm
(a)
Figure 7.6 (a) Safety glass requirement indicated in
shaded areas of glazed door and side panel. (b) Safety
glass requirement indicated in window below 800 mm
from the ffl
Figure 7.5 Internally beaded glazing
Figure 7.5: uPVC casements with internally beaded
sealed units are mostly used nowadays, mainly for the
following two reasons.
●
●
They are thought to be more burglar-resistant.
Being internally beaded means that the glazing operation is done from inside the building, which on
certain jobs – especially those without scaffolding –
can be an advantage.
On this type of window, there is an external upstanding edge, grooved as before, but this time to receive a
so-called firtree gasket, as illustrated, instead of the
wedge gasket. The sealed unit, still on setting blocks
and, if in an opening vent, secured with locating
blocks, is pushed outwards to be hard up against the
firtree-gasket edge, and the internal ‘clip-in’ beads are
pushed and clipped fairly easily into place.
7.3.4 Glazing Safety Issues
Figure 7.6(a)(b): Related to the current Building
Regulations, the 1998 edition of Approved Document
N, Glazing – Materials and Protection, introduced new
provisions covering the safe use of glazed elements in
compliance with the Workplace (Health, Safety and
Welfare) Regulations 1992. As the title implies, these
regulations are aimed at the workplace and apply
mostly to non-habitable buildings such as shops, factories, offices, etc, and only Approved Document N1
applies to dwellings – not Parts N2, N3 and N4. Part
N1 refers to critical locations where people are likely
to come into contact with glazing and where accidents
may occur, causing cutting or piercing injuries. These
critical locations, as illustrated, are identified and
concern (a) the glazing of doors and side panels
between the finished floor level (ffl) and 1.5 m above
and (b) glass in internal or external walls and partitions between finished floor level and 0.8 m (800 mm)
above. The Approved Document lists a number of
alternative solutions to minimise the risk of injury
in these areas. The first of these refers to the most
popular solution, i.e. the installation of safety glass
in any deemed critical areas. Note that five out of
the six glazed units shown in the illustration would
require safety glass.
7.4 WINDOW BOARDS
Windows must be fixed into position before drylining or plastering takes place, to enable a satisfactory
abutment of the wall-lining against the window’s
head and sides. For the same reasons, window boards
are also required to be fixed. These boards appear as a
stepped extension of the sill and project beyond the
plaster faces at the front and sides, like the projecting
nosing of a stair tread. If made of MDF board or timber and fitting up against a wooden casement window,
the back edge is usually tongued into a groove in the
sill. If the window is of uPVC, the window board is
square-edged and only butted and may be held with
a panel adhesive such as Gripfill – or the abutment
may be covered with a small plastic cloaking-fillet or
quadrant held with superglue.
Window Boards
77
7.4.1 Marking and Cutting the
Window Board
7.4.2 Fitting and Fixing the Window
Board (Traditional Method)
Figure 7.7(a): As illustrated, a portion of board about
50 mm in from each end is marked and cut to fit the
window reveals, and the machined nosing shape on
the front edge is returned on the ends, by hand with
a smoothing plane and finished with glasspaper.
Figures 7.7(b) and (c): Packing is usually required
between the window board and the inner skin of
block-work, to level the board across its depth. Pieces
of damp-proof course material, plastic shims or hardboard make ideal packings. If tongue-and-grooved,
the boards are skew-nailed to the wooden sills with
38 mm oval nails or panel pins and fixed through the
packings into the blockwork with either cut clasp nails
or pelleted screw fixings. Packings may be established
about every 450 mm prior to positioning the board, by
using the end offcuts, as illustrated, with the tongue in
the groove, a spirit level on top – or a try-square
against the jambs – while trial packings are inserted.
Reveal-marks
Window
board
Nosing
Returned nosing
(a)
7.4.3 Alternative (Modern)
Window-board Fixings
Boat
level
(a)
Packing
Window-board offcut
(b)
Figure 7.8 (a) Galvanized bracket-shape anchor or
purpose-made, heavy-duty Fixing Band as fixings to the
underside of window boards; (b) Owlett’s screw ties as
alternative fixings
(b)
Cut-nail
fixings
Oval-nail
fixings
(c)
Figure 7.7 Marking and fitting a window board
Figure 7.8(a)(b): Most inner-skin blockwork walls
nowadays use improved thermal blocks and are either
too ‘soft’ (lightly foamed) or too ‘hard’ (densely
foamed) to receive the traditional nail-fixings illustrated in Figure 7.7. Furthermore, the extensive use of
MDF board as a replacement for softwood window
boards over the last decade or so, has added to the fixing problem. This is because MDF is a densely compacted material that does not receive nails as readily as
softwood – especially such bulky fixings as cut clasp
nails; the heads of which would resist being punched
below the surface. For these reasons, the following
alternative methods of fixing are now being used: (a)
Anchors in the form of galvanized or zinc-plated,
bracket-shape right-angles, or similar shaped anchors
purpose-made from heavy-duty (20 gauge) galvanized-steel, multi-holed fixing band, are pre-screwed
78
Fixing Wooden and uPVC Windows
to the underside of the window board prior to fixing,
then, once the board is refitted, nailed or screwed to
the brickwork or blockwork face; and (b) Owlett’s
zinc-plated screw ties are screwed into the underside
of the window board, as illustrated, prior to fixing,
then, once the board is refitted, nailed or screwed to
the wall-face through side lugs, as illustrated. Method
(a) is suitable for dry-lined walls and/or plastered
walls, whereas method (b) is more suitable for plastered walls only.
7.5 BOXFRAME WINDOWS
A
B
(b)
7.5.1 Introduction
Traditional boxframe windows with double-hung, upand-down sliding sashes, sash cords, pulley wheels and
cast-iron weights were extensively used many years
ago and are still very much in evidence in mature and
period properties. For this reason, they will still be
required in their traditional form, if only as replacement windows during maintenance operations.
Furthermore, these elegant windows, offering ideal
top and bottom ventilation – and countless years of
service if well maintained – appear to be making a
comeback nowadays.
7.5.2 Fixing Modern-type Boxframe
Windows
Figure 7.9(a)(b): However, it is unlikely that boxframe
windows would be used in their precise traditional
form in modern dwellings, because the present-day
version dispenses with the box construction, cords,
pulley wheels and weights, and they have solid jambs,
heads and sills – as illustrated – and sliding sashes
hung on patent spiral-balance fittings. Also, for those
who prefer less maintenance, uPVC replicas of these
windows are now produced. Whether of wood or
uPVC, such windows, because of their smaller jambs
and head, would not need to be recessed into the brick
reveals and soffit, making them ideally suitable for fitting against modern cavity walls. Being, in effect, like
wooden casement windows, they would be fixed like
them – or could be fitted into openings and fixed with
Window-fix or Frame-fix sleeved screws.
7.5.3 Fixing (or Replacing)
Traditional Boxframe Windows
Figure 7.10(a): Site measurements can be taken
from the window being replaced or the following
considerations should be borne in mind: The overall
B
A
(a)
Elevation
Vertical
section A-A
Horizontal section B-B
Figure 7.9 (a) Sectional view showing solid jambs of
sliding-sash window; (b) sectional view of solid head
height and width of the boxframe should be at least
12 mm less than the internal, recessed brick opening
to allow for fitting tolerances. The outer linings of the
box should only project 16 mm into the window opening, with the exception of the window’s head in relation to a segmental brick-arch, where the 16 mm
projection is allowed at the extreme ends of the
springing line.
Figure 7.10(b): When positioning the window for
fixing, the wooden sill should be bedded on a generous application of silicone or mastic frame sealant.
Then the frame should be levelled and plumbed with
hardwood wedges driven in each side, top and bottom. They should be placed immediately behind the
ends of the pulley-stile head and the sill – up against
the brickwork. These positions are critical, as they
reduce the risk of causing the frame to bulge.
Traditionally, these windows were skew-nailed
through the two inner-lining’s outer edges into a few
plugged bed-joints of the brickwork and nailed to an
internal wooden lintel above. The method nowadays,
as illustrated, would be to pre-fix right-angled
bracket-shape anchors, similar to those described for
fixing window boards, and face-fix them to the inner
brickwork or blockwork after wedging. Finally, a mastic frame-sealant or silicone should be gunned around
the head and reveals on the outside and the bed-joint
at the sill should be re-gunned on the face edge. The
window board or nosing piece can now be fixed to
complete the job.
Boxframe Windows
A
∗
O/A height minus 12 mm
16 mm
B
B
∗
A
Elevation
O/A width minus 12 mm
Vertical
section A-A
16 mm
(a)
∗ Side-wedging positions
16 mm
Horizontal section B-B
∗∗
∗
∗
∗∗
(b)
∗ Side-wedging positions
∗ ∗ Top and bottom fixing-anchors
Figure 7.10(a) Site measurements for box-frame windows; (b) top and bottom fixing-anchors and wedging positions
79
8
Fixing Floor Joists
and Flooring
8.1 INTRODUCTION
Although reinforced concrete floors of all kinds are
used in large buildings such as blocks of flats or office
blocks, timber floors are still widely used in domestic
dwelling houses, especially above ground-floor level.
Such floors were predominantly formed with traditional timber joists, but patented, engineered timber
joists – covering wider spans – are also being used
nowadays. Floors are generally referred to according
to their position in relation to the ground. These
range upwards from ground-floor level, first floor,
second floor and so on; they may also be classified
technically as single or double floors, according to the
cross-formation of the structural members.
8.1.1 Single and Double Floors
Figure 8.1 (a): Suspended timber floors consist of
board-on-edge like timbers known as joists, spaced
parallel to each other at specified centres across the
Floor joists
Cavity
walls
floor and, in the case of a single floor, resting between
the extreme bearing points of the walls. In the case of
a double floor, they rest on intermediate support(s) and
the extreme bearing points of the walls. The top surface of the joists can be covered with various materials
such as timber T&G floor boards, chipboard T&G
flooring panels, plywood T&G flooring panels or
Sterling OSB (oriented strand board) T&G flooring
panels – and the underside of the joists covered with
ceiling material such as Gyproc plasterboard.
8.1.2 Spacing of Joists
Figure 8.1(b): The spacing of the joists is related to the
thickness of floor boarding or sheeting to be used;
400 mm centres (c/c) is required in domestic dwellings
using ex. 22 mm T&G timber boarding, 18 mm chipboard T&G panels, 18 mm plywood T&G panels or
15 mm OSB T&G flooring panels. When the joists are
spaced at 600 mm centres, three of these materials need
to be thicker: the T&G timber boarding should be ex.
25 mm, the T&G chipboard should be 22 mm, and the
OSB T&G panels should be 18 mm. Tongue and
groove flooring panels are critically 2400 or 2440 mm
long and 600 mm wide. The length needs to be considered when setting up the joists, because the staggered
Thickness
Single floor
Sawn joists
Depth
Theoretical
spacing
Floor joists
Encased
steel beam
Practical
spacing
Double floor
(a)
Figure 8.1 (a) Suspended floor joists; (b) spacing of joists
(b)
Ground Floors
cross-joints of these panels must bear centrally on the
joists. Therefore, if the panel is a metric modular length
of 2400 mm, then the joist-spacings should be
2400 6 ⫽ 400 mm c/c., or 2400 ⫼ 4 ⫽ 600 mm c/c.
However, if the panel is based on an imperial length of
8 ft, converted to 2440 mm, then the joist-spacings
should be 2440 ⫼ 6 ⫽ 406.6 mm c/c (16 in) or
2440 ⫼ 4 ⫽ 610 mm c/c (24 in). On upper floor levels,
these considerations also apply to the cross-joints of the
plasterboard sheets to be used later on in the ceilings
below.
8.1.3 Size of Joists
The sectional size of joists is always specified and need
not concern the site carpenter or builder. The subject
enters into the theory of structures and mechanics and
is, therefore, a separate area of study. However, for
domestic dwellings, a simple rule-of-thumb calculation
has existed in the trade for many years, expressed as
span
⫹2
2
but this is only an approximate method, which errs on
the side of safety. In Imperial measurement, this was
expressed as
depth of joist in inches ⫽
span in feet
⫹2
2
depth of joist in centimetres
⫽
span in decimetres
⫹2
2
For example, for a joist span of 4 m
depth of joist ⫽
40
⫹ 2 ⫽ 22 cm ⫽ 220 mm
2
The thickness of joists, by this method, is usually
standardized at 50 mm. The nearest commercial size,
therefore, would be 225 ⫻ 50 mm.
8.1.4 Structurally Graded Timber
By comparison, table A1 for floor joists, given in The
Building Regulations’ AD (approved document) A1/2,
specifies joists of 220 ⫻ 38 mm section at 400 mm
centres, for a maximum span of 4.43 m. However, it
should be noted that SC3 (strength class 3 – now
referred to as C16) structurally graded timber is
specified. Such timber is now commonly relied upon
for structural uses and is covered by BS 4978 – and BS
5268: Part 2: 1991. Certain standards and criteria are
laid down regarding the size and position of knots,
the slope of grain, etc., and the assigning of species and
grade combinations to strength classes SC3 (C16)
and SC4 (C24).
8.2 GROUND FLOORS
For example, if the span of the joists is 14 ft 0 in
depth of joist ⫽
14
⫹ 2 ⫽ 9 in
2
8.2.1 Suspended Timber Floor
In metric measurement, the formula is converted to
Figure 8.2(a): The first of the various types of ground
floor that involves the carpenter, is the suspended timber
Sleeved air vents below DPC
Cavity
walls
Honeycombed
sleeper walls
Wall
plates
Fender
wall
Concrete
hearth
Joist
81
Joist
Figure 8.2 (a) Part-plan
view of exposed floor
82
Fixing Floor Joists and Flooring
floor. Traditionally, joists of 100 ⫻ 50 mm section, were
generally used, spaced at 400–600 mm centres. They
rested on 100 ⫻ 50 mm timber wall-plates and were
skew-nailed to these from each side with 100 mm
round-head wire nails. The wall plates were bedded on
half-brick-wide sleeper walls with a damp-proof-course
material sandwiched in the mortar joint. The sleeper
walls, which were honeycombed for underfloor air circulation, were traditionally built at 1.8 m centres to support the 100 ⫻ 50 mm sawn joists. Nowadays, if using
structurally-graded timber, designated as SC3 (structural
class 3) – also known as C16 (class 16) – the walls
would be built at 2.08 m centres to support the joists at
400 mm c/c, and 1.67 m centres to support the joists at
600 mm c/c. If SC4 (structural class 4) – also known as
C24 (class 24) – joists were used, the walls could be built
at 2.2 m centres to support the joists at 400 mm c/c, and
1.82 m centres to support the joists at 600 mm c/c. The
honeycombed sleeper walls were usually built onto the
concrete oversite – if adequate – rather than onto separate foundations.
8.2.2 Regulation Requirements
Since this book was first published in 1998, radical
changes have been made to the Building Regulations’
Part L of Schedule 1, concerning the Conservation of
fuel and power. In an attempt to reduce CO2 emissions
and the effects of global warming, amendments to
Approved Document L1 (covering dwellings) and
Approved Document L2 (covering all buildings other
than dwellings), came into force in April 2002, setting
guidelines for higher levels of insulation and more
efficient heating and lighting systems in dwellings and
other buildings. ADL1 offered three methods to use
for demonstrating that provision had been made to
limit heat loss through the building fabric. These were
(1) Elemental Method, (2) Target U-value Method
and (3) Carbon Index Method. The Elemental
Method was the less complex and aimed at meeting
(or keeping below) the maximum U-value ratings (the
rate at which heat passes through a material, or a mixture of different materials) of the individual elements –
walls, floors and roofs, etc – in a dwelling. As a guide
to this, Maximum U-value Tables for the building’s
exposed elements were given for reference.
However, further amendments have now been made
and ADL1 and ADL2 have been replaced by four new
Approved Documents, which came into force in April
2006. All entitled Conservation of fuel and power,
ADL1A covers new dwellings, ADL1B covers existing
dwellings, ADL2A covers new buildings other than
dwellings and ADL2B covers existing buildings other than
dwellings. Under these new regulations, the methods of
compliance have changed and the Elemental Method,
plus the Target U-value Method are now omitted from
being used in new dwellings. The method of calculation
for the energy performance is now referred to as the
Target CO2 emission rate (TER) calculations, which
are applied to the whole building. In the case of existing
dwellings, under ADL1B, the energy performance
can be based on an Elemental Method to comply with
U-value targets for the thermal elements.
As illustrated at (b) and (e), a possible way of
upgrading this type of floor to meet the new regulations, would be to pack 100 mm thick mineral-wool
quilt insulation (such as Crown Wool) between the
joists, laid on support netting, and overlay the joists
with 48 mm thick Celotex GA2000 (a rigid foam
insulation slab). This would need to be supported on a
sub-floor of 15 mm chipboard or OSB and overlaid
with a finished floor decking.
See figure 8.2(e)
Floating floor
Celotex GA2000
15 mm subfloor
Sleeved
air vent
100 ⫻ 50 Joists
Wall plate
DPC
NLT 150
NLT 75
DPC
NLT 150
Oversite concrete
Trench-fill
foundation
Figure 8.2 (b) Sectional view through suspended
ground floor
Figure 8.2(b): Part C of the Building Regulations,
which is concerned with protecting buildings from
dampness, requires the site to be effectively cleared of
turf and other vegetable matter and the concrete oversite to be of 100 mm minimum thickness and to a
specified mix, laid on clean hardcore and finished with
a trowel or spade finish. The top surface of the concrete
oversite should not be lower than the highest level of
the ground or paving adjoining the external walls of the
building. The space a bove the concrete to the underside of the wall plates must not be less than 75 mm and
not less than 150 mm to the underside of the joists. The
space should be clear of debris (broken bricks, shavings,
offcuts of timber, etc.) and be adequately through-ventilated with a ventilation area equivalent to 1500 mm2
per metre run of wall in two opposite external walls.
Alternatively, the ground surface may be covered
with at least 50 mm thick concrete, laid on a DPM of
Ground Floors
1200 gauge polythene sheeting (or 1000 gauge if conforming to Agrément Certificate and PIFA standard),
laid on a suitable, protective bedding material, i.e.,
sand. Note that if this alternative oversite covering is
used, separate foundations would be required to support any honeycombed sleeper walls that may be
required to support the joists.
Where external ground levels are higher than the
internal levels of the oversite concrete, the oversite
concrete must be laid to slope and fall to a perimeter
outlet in the form of a gulley, sump or soakaway, above
the lowest level of the external ground.
As illustrated, the damp-proof course in the cavity
wall should be not less than 150 mm above the adjoining ground or paving – and the top of the cavity-fill
should be not less than 150 mm below the level of the
lowest damp-proof course (as indicated in Figure 8.9
for a surface-battened floor).
83
Figure 8.2(d): When the wall plates are set, the joists
can be cut to length and fixed in position by nailing or
anchoring – bearing in mind that the ends of the joists
should also be kept away from the walls by approximately 12 mm. The first joist is fixed parallel to the
wall, with a 50 mm gap running along its wall-side
face, to create more reliable edge-bearings and to
facilitate easier board fixings. The second joist can be
fixed at 400 mm centres from the first if timber boarding is to be used, but if edge-finished flooring panels
are to be used, then the second joist should be fixed at
400 or 406 mm ⫹ 12 mm expansion gap from the wall –
not the first joist. Subsequent joists are fixed at the
required spacing until the opposite wall is reached.
The last spacing is usually under or slightly over size.
Joists joined on sleeper walls are usually overlapped, as
illustrated, and side-nailed.
8.2.3 Bedding the Wall Plates
Figure 8.2 (c) Wall-plate joints
Figure 8.2(c): The first operation is to cut the wall
plates to length, bearing in mind that the ends of
these should be kept away from the walls by approximately 12 mm. After laying and spreading mortar on
the sleeper walls, rolling out and flattening the DPC
material, more mortar is laid and the wall plates are
bedded and levelled into position with a spirit level.
Once the first plate has been bedded and levelled, the
others, as well as being levelled in length, must also be
checked for level crosswise, using the first plate as a
datum. If any wall plate cannot be laid in one piece, or
changes direction, it should be jointed with a half-lap
joint.
8.2.4 Laying and Fixing the Joists
Figure 8.2 (e) Cross-section through floor at figure
8.2(b), showing floating floor on 48 mm Celotex
GA2000 slab insulation supported on a subfloor of
chipboard or OSB. 100 mm thick Crown wool packed
between 100 ⫻ 50 mm joists, laid on support-netting
8.2.5 Providing a Fireplace and
Hearth
NLT 500
Hearth
Flagstone
DPC
Wall plate
Fender
wall
100 mm oversite concrete
100 mm hardcore
Honeycombed sleeper wall
Wall plate
Figure 8.2 (d) Joining joists on sleeper walls
Figure 8.2 (f) Sectional view through hearth
Figure 8.2(f ): Although omitted in recent years, there
seems to be a demand for – and some return to –
traditional fireplaces able to take a gas or electric fire
in the lounge or living room. Therefore, if a fireplace
84
Fixing Floor Joists and Flooring
and the required concrete hearth are to protrude into
the floor area, the hearth can be contained below floor
level within a one-brick-thick fender wall built around
the fireplace. The ends of the joists rest on wall plates
supported by half the thickness of the fender wall.
The other half supports the concrete hearth. Part J of
the Building Regulations requires that no timber
should come nearer to the fire opening than 500 mm
from the front and 150 mm from each side (Figures
8.2(f ) and (g)). Although not demanded by the
Regulations, ideally the timbers should be pre-treated
or treated on site with a preservative.
Normal
For access traps
Square heading joint
Splayed heading joint
Deeper on top for strength
(a)
Gaps to ensure good
fit on top surface
150
500
Part-plan view
of boarded floor
150
Figure 8.2 (g) Regulation size of hearth
8.2.6 Flooring Materials
The flooring material can be tongue and groove
(T&G) timber boarding, flooring-quality chipboard
T&G flooring panels, plywood T&G flooring panels
or OSB (oriented strand board) T&G flooring panels.
Their thicknesses must suit the joist-spacing, as
described above.
(b)
Figure 8.3 (a) The right way up for T&G boards;
(b) Recommended dovetail-fixings
be two nails to each board fixing, about 16 mm in
from the edges. If using lost-head nails, each nail
should be driven in at an angle to create the effect of a
dovetailed fixing. Just prior to fixing, boards must be
sorted and turned up the right way, as illustrated.
8.3.1 Fixing Procedure
Floor
cramp
Folding
wedges
Side of joist
8.3 LAYING T&G TIMBER
BOARDING
Figure 8.3: When laying boarded floors, cross-joints
(end grain or heading joints) should be kept to a minimum, if possible, and widely scattered. No two heading joints should line up on consecutive boards. On all
sides, boards should be kept away from the walls by
approximately 12 mm. This is to reduce the risk of
picking up dampness from the walls and to allow for
any movement across the boards due to expansion. All
nails should be punched in 2–3 mm below the surface.
Boards should be cramped up and fixed progressively
in batches of five to six at a time. Tongues and grooves
should be protected during cramping by placing offcuts of boarding between the cramps and the floor’s
edge. Fixings – cut floor-brads or lost-head wire nails –
should be at least 2--12 times the thickness of the board,
i.e. for 20 mm boards use 50 mm nails. There should
Plan view
Figure 8.4 Cramping methods
Figure 8.4: Cramping can be done with patent metal
floor cramps which saddle and grip the joists when
wound up to exert pressure on the boards, or by using
sets of folding wedges cut from tongued-and-grooved
offcuts, 200–300 mm long. The first board is nailed
down about 12 mm away from the wall, with small
wedges inserted to retain the gap during cramping.
Five or six more boards are cut to length and laid.
When using wedges as cramps, a seventh board is cut
and partially nailed, set away from the laid boards at a
Floating Floor (with Discontinuous Support)
distance equal to the least width of the pre-cut folding
wedges. The wedges are inserted at about 1–1.5 m
centres and driven in to a tight fit. The boards, having
been marked over the centre of the joists, are then
nailed. When complete, the wedges and the seventh
board are released. This board becomes the first of
another batch of boards to be laid and the sequence is
repeated until the other wall is reached. The final
batch of boards are levered and wedged from the wall
with a wrecking bar or flooring chisel, then nailed; the
last board having been checked and ripped to width to
ensure a 12 mm gap from the wall on completion.
8.4 FLOATING FLOOR (WITH
CONTINUOUS SUPPORT)
T&G flooring panels
Polythene vapour check
Polystyrene underlay
100 mm oversite
DPM sandwich
85
sealed with water-proof adhesive tape, such as Sellotape
1408. Next, the tongued-and-grooved panels are laid,
taking care not to damage the polythene and leaving an
expansion gap of 10–12 mm around all walls and other
abutments. The cross-joints must be staggered to form a
stretcher-bond pattern and all joints should be glued
with polyvinyl acetate adhesive, such as Febond. Laying
is started against the wall from one corner and when the
other corner is reached, any reasonably-sized offcut can
be returned to start the next row. Otherwise half a sheet
should be cut to do this. Temporary wedges should be
inserted around perimeter gaps until the glued joints set.
A protective batten or flooring-offcut should be held
against the flooring’s edge when hammering panels into
position. Finally, before fixing the skirting, the perimeter
gap should be checked and cleaned out, if necessary.
8.4.2 Other Points to Note
Partition
Access
panel
DPC
Support-battens
Hardcore
Trench-fill
foundation
Doorway
Batten
Figure 8.6 Battens required within the insulation
Figure 8.5 Floating floor
Figure 8.5: This type of floor, consisting of manufactured T&G flooring panels, laid and floating on closebutted 100 mm thick rigid polystyrene sheets, such as
Jabfloor Type 70, and held down by its own weight and
the perimeter skirting, turns a cold unyielding concrete
base into a warm resilient floor at relatively low cost.
The flooring panels used may be 18 mm T&G chipboard (preferably moisture-resistant grade), or 18 mm
T&G plywood, with laid-sizes of 2400 ⫻ 600 mm or
2440 ⫻ 600 mm. Sterling OSB T&G flooring panels
are not recommended for use on floating floors.
8.4.1 Laying Procedure
After the closely butted sheets of Jabfloor insulation
have been laid over the concrete floor, a roll of 1000
gauge minimum thickness polythene sheeting is rolled
out and laid over it to act as a vapour check. This should
be turned up at least the flooring-thickness at the wall
edges and all joints should be lapped by 300 mm and
Figure 8.6: Any pipes or conduits to be accommodated
within the insulation material must be securely fixed to
the oversite concrete and the thickness of insulation
material may need increasing to exceed the diameter of
the largest pipe. Hot-water pipes should not come in
direct contact with any polystyrene underlay.
Preservative-treated battens should be fixed to the slab
to give support to any concentrated load on the floor,
such as a partition or the foot of a staircase, etc. Such
battens are also required where an access panel is to be
formed and where the floor abuts a doorway, as illustrated. As well as being stored carefully on site, flooring
panels should be conditioned by being laid loosely in the
area to be floored for at least 24 hours before fixing.
8.5 FLOATING FLOOR (WITH
DISCONTINUOUS SUPPORT)
Figure 8.7: This type of floor is referred to as a battened floating floor. Staggered flooring panels are laid
and fixed to a framework of 50 ⫻ 50 mm battens (the
86
Fixing Floor Joists and Flooring
T&G flooring panels
Polythene vapour check
Quilt underlay
100 mm oversite
DPM sandwich
50 ⫻ 50 battens
T&G flooring panels
Polythene vapour barrier
12 mm insulation board
DPM sandwich
DPC
DPC
Hardcore
Hardcore
Trench-fill
foundation
Figure 8.7 Battened floating floor
final notes on upper floors (page 94) give fixing details
of panels on joists, which also apply here in fixing
panels to battens). The battens are laid unfixed on
48 mm thick Celotex GA2000 rigid-insulation slabs,
resting on a dry and damp-proofed concrete oversite
and covered with a vapour barrier as described previously. When fixed to the battens, the floor is floating
on the insulation and is held down by its own weight
and the perimeter skirting.
8.6 FILLET OR BATTENED
FLOORS
Another type of floor to be considered, consists of
50 ⫻ 50 mm sawn fillets or battens, spaced at 400 mm
or 600 mm centres and either embedded in the concrete over-site or fixed on top. Both of these applications are covered by Part C of the Building
Regulations’ Approved Document Regulation 7, and
the detailed examples given here are aimed at meeting
the requirements for timber in floors supported directly
by the ground.
8.6.1 Embedded-fillet Floor
Figure 8.8: The timber fillets are splayed to a dovetail
shape and must be pressure-treated with preservative
in accordance with BS 1282: 1975, Guide to the choice,
use and application of wood preservatives, prior to being
inserted in the floor. The concrete oversite must incorporate a damp-proof sandwich membrane consisting of
a continuous layer of hot-applied soft bitumen of coal
tar pitch not less than 3 mm thick, or at least three
coats of bitumen solution, bitumen/rubber emulsion
Trench-fill
foundation
Figure 8.8 Embedded-fillet floor
or tar/rubber emulsion. After the DPM has been
applied and has set, the splayed fillets, having been cut
to length and the cut-ends resealed with preservative,
are bedded in position at the required centres and
levelled. This can be done by placing small deposits
of concrete in which the fillets are laid and tamped to
level positions. When set, the top half of the concrete
sandwich is laid, using the fillets as screeding rules.
Again, 48 mm Celotex GA2000 rigid foam
insulation can be used.
8.6.2 Surface-battened Floor
DPC
DPM
Bulldog
regular type
floor clip
Short-leg
acoustic
floor clip
Figure 8.9 Surface-battened floor
Figure 8.9: A damp-proof sandwich membrane, as
described above, is required and must be joined to the
damp-proof course in the walls. Standard or acoustic
Bulldog floor clips can be used to hold the battens in
position at the required spacing. The clips are pushed
into the plastic concrete at 600 mm centres within 30
minutes of laying and levelling. A raised plank is
placed across the concrete to support the operative
Engineered-Timber Floors
and a batten marked with the clip-centres is used to
act as a guide for spacing and aligning the clips. When
laying the battened floor, after the concrete is set and
thoroughly dry, the ears of the clips are raised with the
claw hammer, the battens are inserted and fixed with
special friction-tight nails supplied with the clips. As
illustrated, both floors may be insulated with 48 mm
Celotex GA2000, covered with a polythene vapour
barrier prior to being floored with T&G chipboard,
plywood or OSB flooring panels.
8.7 BEAM-AND-BLOCK FLOOR
Precast floor beam
T&G flooring panels
Polythene vapour barrier
25 mm Jablite insulation
87
8.8 ENGINEERED-TIMBER
FLOORS
8.8.1 Introduction
Engineered-timber products such as beams and joists
have been around for many years now – in various
forms – but have previously been mostly used in
buildings of timber frame construction. However, they
are now also used in buildings and dwelling houses of
traditional masonry construction. Apart from the ecological benefit gained by these products using less of
the limited forest resource compared to traditional
solid-timber beams and joists, they can be manufactured to bridge larger spans between bearing points.
DPC
Not less
than
75 mm
Ventilated void
Figure 8.10 Floating floor on beam-and-block
construction
Figure 8.10: This is a modern construction used at
ground floor level on dwelling houses. The precast
reinforced concrete floor-beams have to be ordered to
the lengths and number required. They take their
bearings on the inner-skin of blockwork and, as illustrated, must be at least 75 mm above ground level to
the underside of the beams. They are spaced out to
take the length of 440 ⫻ 215 ⫻ 100 mm standard wall
blocks, laid edge to edge and resting on the beams’
protruding bottom-edges. A row of cut blocks is
inevitably required along one side, as illustrated. The
gaps between blocks and beams are filled with a
brushed-over sand-and-cement grout. The void
beneath the precast beams should be provided with
through-draught ventilation, continuous through any
intermediate cross sleeper-walls, with an actual ventilation area equivalent to 600 mm2 per metre run of
wall. The floating floor laid on this sub-floor construction will be as described previously under ‘Laying
Procedure’. Note: By using ADL1B’s Elemental
Method of calculating energy performance, the insulation shown above the beam-and-block floor, would
need to be either 100 mm (or two layers of 50 mm)
Jabfloor Type 70, or 48 mm slabs of Celotex GA2000.
Figure 8.11 (a) Sectional shape of a TJI® joist
Sealant
Sleeved
air vent
DPC
NLT 150
NLT 150 mm
Figure 8.11 (b) TJI® joists to ground floor level. Insulation
omitted for clarity (see figure 8.11(c))
Figure 8.11(a)(b): The details illustrated here
represent a suspended timber floor at ground floor
level using engineered timber joists manufactured by
88
Fixing Floor Joists and Flooring
the Trus Joist company. The floor is referred to as the
Silent Floor® System and the joists as TJI® joists; TJ
obviously being the manufacturer’s initials and the ‘I’
being a trade reference to an ‘I Beam’: the joists’ sectional shape, as illustrated at (a). The joists are
described as being made of continuous Microllam®
laminated veneer lumber (LVL) flanges, which are
groove-routed to house a central web of Performance
Plus™ OSB (oriented strand board). In manufacture,
the three components are joined together by a highspeed bonding process using a waterproof, synthetic
resin adhesive and radio-frequency heating whilst
under pressure.
Trus Joist’s detailed illustrations in their technical
literature show the TJI® joists built in to the innerskin blockwork and state that where the external
ground levels are higher than the internal subfloor
levels, the internal subfloor surface (oversite concrete)
should be sloped to fall to a perimeter drain, gulley,
sump or soakaway – in compliance with Part C of the
Building Regulations, as detailed in section 8.2.2
(Regulation Requirements) of this chapter. If required –
to keep the joists to a shallower depth over areas with
large spans – intermediate, honeycombed sleeper walls
can be used in this system.
8.8.2 Insulation Details
energy performance of the whole building. However, if
the floor only needed to comply with Approved
Document L1B, for existing dwellings, the Elemental
Method of complying with the U-value targets could
be used. By this method, the insulation needs to be at
least 200 mm thick between the webs – and packed into
the gaps between the joists and the wall.
8.9 UPPER FLOORS
8.9.1 Timber Joists
Trimmed opening
for stairwell
B
A
A
C
D
D
B
D
D
D
D
D
A = Bridging joist
B = Trimmer joist
C = Trimming joist
D = Trimmed joist
D
C
A
A
D
B
D
C
A
A
Herringbone strutting
(see Figure 8.19 for details)
Figure 8.11 (c) 200 mm thick Crown wool packed
between TJI® joists, laid on support-netting
Figure 8.12 (a) Part-plan views of alternative joistarrangements around trimmed opening
Figure 8.11(c): Typical insulation details for these
floors are shown in the Trus Joist literature and are
represented here. Reference is made to a mineral-wool
quilt-type insulation being packed tightly between the
webs of the TJI® joists. To achieve this, a trough or tray
has to be formed at the bottom of the joists. This is
done by fixing (stapling) galvanized wire, plastic mesh
or a breather membrane to the bottom of the joists. In
practical terms, this membrane would have to be fixed
to the face-side edges of the bottom flanges, or laid
snake-fashion over the joists. Alternatively, a slab-type,
solid foam insulation may be used without the need for
supporting mesh. Note that to comply with the
amended regulations and guide details in Approved
Document L1A, for new dwellings (outlined under
8.2.2 Regulation Requirements of this chapter), the
insulation of this floor would be subject to so-called
Target CO2 emission-rate (TER) calculations for the
Figure 8.12 (a): In dwelling houses, suspended timber
floors at first-floor level and above are usually single
floors comprising a series of joists supported only by
the extreme bearing points of the structural walls.
These joists are called bridging joists, but any joists
that are affected by an opening in the floor, such as for
a stairwell or a concrete hearth in front of a chimneybreast opening are called trimmer, trimming and
trimmed joists, as illustrated. Because the trimmer carries the trimmed joists and transfers this load to the
trimming joist(s), both the trimmer and the trimming
joists are made thicker than the bridging joists by
12.5–25 mm, or double joists, bolted together, are
used. The depth of the joists, as mentioned in the
opening pages of this chapter, does not usually concern the site carpenter or builder, such structural detail
being the responsibility of the architectural team.
However, if ever needed, the size of joists relevant to
Upper Floors
the span and joist-spacing, can be gained easily
enough by reference to Tables A1 and A2 for floor
joists in The Building Regulations’ Approved Document
A from HMSO Publications Centre or bookshops.
89
8.9.3 Blind Tenon and Housing Joints
B
8.9.2 Framing Joints
B
B
B
D
D
D
D
T
D
—
2
Trimming joist
Bevelled
haunch
Blind tenon
Trimmer
D
—
6
Tenon
Plain stoppedhousing
Bevelled and dovetailed
stopped-housings
D
Clearance
1 in 10
wedge
T
—
3
T
—
4
D
—
4
Tusk
D
—
4
Figure 8.12 (c) Traditional framing joints
D
= Size of square mortice
T
Figure 8.12 (b) Traditional tusk tenon joint (T ⫽ thickness;
D ⫽ depth)
Figure 8.12 (b): Traditionally, a tusk tenon joint was
used between the trimming joist and the trimmer –
and is given here for reference only. This joint was
proportioned as shown and was set out and cut on site
with the aid of hand tools. The wedge was cut to a
shallow angle of about 1 in 10 ratio to inhibit rejection, made as long as possible and, upon assembly, was
driven into a offset draw-bore mortice in the tenon.
The offset clearance that was needed to effect the
drawn-tight fit between the two structural members,
is indicated in the illustration. The slope on the bottom of the wedge was to facilitate entry and the top
slope lent itself to the angle of the hammer blow with
less risk of shearing the short grain. When jointing,
particular care was taken to ensure that the bearing
surfaces of the tusk and tenon were not slack against
the stopped housing and the mortice.
BR
CL
Trip-L-Grip BR and CL type
Figure 8.12 (c): Traditional joints used between
trimmed joists (D) and trimmer joist (B), varied
between a blind tenon and a plain stopped-housing.
Other joints, seen more in textbooks than in practice,
included a bevelled stopped-housing and a dovetailed
stopped-housing. The blind tenon joint was made to
the same proportions as the tusk tenon, but did not
have a wedge or projecting tenon. The plain stoppedhousing joint was set out and gauged to cut into the
trimmer 12.5 mm on the top edge and half the joistdepth on the side. It was quickly formed by making
three diagonal saw cuts across the grain (two on the
waste side of the lines, one in the mid-area), chopping
a relief slot at the bottom of the housing and chiselparing from above.
8.9.4 Modern Framing Anchors
Figure 8.13: Metal timber-connectors are now extensively used to replace the above-mentioned joints, in
the form of metal framing anchors and, more commonly, timber-to-timber joist hangers. The advantages
to be gained in using these connectors are a saving of
labour hours and, in the case of the hangers, more
CL
Trip-L-Grip CL and CR type
CR
Figure 8.13 Modern
framing anchors
90
Fixing Floor Joists and Flooring
effective support of the trimmer or trimmed joists, by
the bearing being at the bottom of the load. However,
it must be mentioned that traditional framing joints
have held up to the test of time in houses of several
hundred years of age. When using sherardized framing anchors, such as MAFCO Trip-L-Grip, for floor
joists, the loads to be carried are such that each
trimmed joint should comprise both a B type and a C
or two C type anchors. When using two C types (CL
and CR), one on each side of the joist, they should be
slightly staggered to avoid nail-lines clashing. The
anchors are recommended to be fixed with 3 mm
diameter by 30 mm sherardized wire nails.
8.9.5 Timber-to-timber Joist Hangers
Type TTS
for joists
up to
175 mm
deep
Type TTL
for joists
up to
225 mm
deep
8.9.6 Double Floors
Figure 8.15 (a): The sensible structural rule of timber
joisted floors, is that the joists should always bridge
across the shortest span of an area, unless a double
floor is required, whereby a steel beam (or beams)
bridges the shortest span and the timber joists run the
longest span, bearing on the intermediate beams(s), as
illustrated. The protruding beam at ceiling level is
encased in several ways to achieve fire-resistance and
a visual finish. One way of doing this is to make a
quantity of U-shaped frames – known as cradles or
cradling – using 50 ⫻ 50 mm or 38 ⫻ 38 mm timber,
with lapped or half-lapped, clench-nailed joints at each
corner, and fix them, one to each joist-side, as
indicated at Figure 15(b), close to the beam’s bottom
TTL
Figure 8.14 Timber-to-timber
joist hangers
Figure 8.14: Steel joist hangers, such as those manufactured by Catnic–Holstran, type TT (timber to timber), S and L (short and long), are made from 1 mm
galvanized steel with pre-punched nail holes. With
the aid of a hammer, the straps are easily bent over the
joists, as illustrated, and fixed with 32 mm galvanized
plaster-board nails. Another advantage of the thingauge metal is that hangers do not require housing
into the top or bottom edges of the joists. Although
perhaps not structurally necessary, it is advisable to
place nail-fixings in all the available fixing holes.
and flange-edges. These frames are then clad with
12.5 mm plasterboard or other such non-combustible
material.
8.9.7 Solid-wall Bearings
Figure 8.16: The old practice of building the ends of
joists into solid (non-cavity) walls is now frowned
upon, because of the increased risk of timber decay
10 mm shrinkage gap
L/H joist
R/H joist
(a)
Figure 8.15 (a) Double floor; (b) cradling
(b)
Strutting
Damp walls
affecting
timber
91
TW type joist hanger
Joist
Joist
Wall
plate
Old practice
Modern practice
Figure 8.16 Solid-wall
bearings
Temporary
positioningbatten
Joist
TWR type
hooked
joist hanger
through lateral damp-penetration. As illustrated, the
modern practice is to use steel joist hangers, such as
those manufactured by Catnic–Holstran, type TW
(timber to wall), made from 2.5 mm galvanized steel.
When fixing, 32 mm galvanized plasterboard nails are
recommended. Owing to a double metal-flange on the
bottom, equalling a thickness of 5 mm, the bottom
edge of the joists require notching out to achieve a flat
surface for the pasterboard ceiling.
8.9.8 Cavity-wall Bearings
Figure 8.17: TW (timber to wall), or, as illustrated,
TWR (timber to wall return) joist hangers with a
turndown top flange to ensure correct and safe
anchorage, especially when there is insufficient weight
above, may be used for cavity walls. Alternatively, the
ends of joists, which should be treated with timber
preservative, are positioned, levelled up and built into
the inner skin of the cavity wall. Care must be taken
to ensure that the joists do not protrude past the
inner face of the bearing-wall, into the cavity. The
temporary positioning-batten, illustrated, should be
attached to the scaffold or return wall at its end(s) to
create stability and to stop the joists toppling sideways
until they are built in.
Joist
Alternative
built-in
bearing
Figure 8.17 Cavity-wall
bearings
8.10 STRUTTING
8.10.1 Introduction
Strutting in suspended timber floors is used to give
additional strength by interconnection between joists.
This removes the unwanted individuality of each joist
and effects equal distribution of the weight and prevents
joists bending sideways. Struts should be used where
spans exceed 50 times the joist thickness. Therefore,
with 50 mm thick joists, a single row of central struts
should be used when the span exceeds 2.5 m and two
rows are required for spans over 5 m and up to 7.5 m.
8.10.2 Solid Strutting
Solid struts
Figure 8.18 Common practice of strutting
Joists
92
Fixing Floor Joists and Flooring
Figure 8.18: The common practice of strutting the
floor with solid noggings is frowned upon technically
as adding unnecessary weight and creating an inflexible floor. However, Section 5 of the New Build
Policy Technical Manuals recommends that solid
strutting should be used instead of herringbone
strutting where the distance between joists is greater
than three times the depth of the joists. (Note that the
manuals mentioned here are registered-builders’
guidance notes supplied by Zurich Municipal
Insurance, whose surveyors monitor the building work
during construction and issue a certificate on completion, guaranteeing the building’s fitness for a period of
ten years. This scheme is similar to the one run by the
NHBC.)
8.10.4 Catnic Steel Joist-struts
8.10.3 Herringbone Strutting
8.10.5 Batjam Steel Joist-struts
Strut
material
Fixing
lug
Figure 8.20 Catnic steel joist-struts
Figure 8.20: As illustrated, two types of galvanized
steel herringbone struts are produced to compete with
traditional wooden strutting. The first type, by
Catnic–Holstran, have up-turned and down-turned
lugs for fixings with minimum 38 mm round-head
wire nails. As before, fixing is done from above.
∗
Pencil
Vertical section
Fixed
row of
struts
∗
Marking
position
(a)
cL
Joist
depth
–20 mm
Figure 8.21 Batjam steel joist-struts
Plan view
Figure 8.19 Plan and sectional view of
herringbone strutting
Figure 8.19: This traditional method of strutting, using
38 ⫻ 38 mm or 50 ⫻ 38 mm sawn timber, although
still effective and occasionally used, nowadays has to
compete for speed with struts made of steel. The
method of fixing involves marking a chalk line across
the joists, usually in the centre of the floor as stipulated
in the introductory notes. From this, marks are squared
down the sides of the joists and – in the case of timber
strutting – another line is struck on top with the chalk
line, parallel to the first and set apart by the joist-depth
minus 20–25 mm. As illustrated, the strutting material
is laid diagonally within these lines and marked from
below to produce the required plumb-cuts (vertical
faces of an angle). Cutting and fixing the struts is done
in a kneeling position from above, using 50–63 mm
round-head wire nails. Prior to fixing the struts, the
joists running along each opposite wall should be
packed – technically wedged – and nailed immediately
behind the line of struts. As indicated at (a), a sawcut
can be made at the end of each strut to receive the nail
fixing and eliminate splitting.
Figure 8.21: The second type, with the well-known
‘BAT’ trademark, has forked ends which simply bed
themselves into the joists when forced in at the bottom
and pulled down firmly at the top. This time, fixing is
done from below. One minor disadvantage with steel
strutting, which is made to suit joist centres of 400, 450
and 600 mm, is that there are always one or two places
in most floors that do not conform to size and require
reduced-size struts. When this occurs, it is necessary to
use a few wooden struts in these areas.
8.10.6 Fixing-Band Strutting
Figure 8.22 Fixing-Band strutting
Figure 8.22: Another metal fixing-device sometimes
used for strutting, is Fixing Band. This is comprised of a
20 gauge ⫻ 20 mm wide galvanized-steel band, usually
in 10 m rolls. The band is perforated with continuous
fixing holes and is easily bent to any required shape and
Strutting
cut to length with a hacksaw. As indicated in the illustration, the band is fixed to form a continuous, taut
zigzag pattern over the tops and bottoms of the joists.
This is best done up against a line marked over and
squared down the face of each joist. Then another band
is fixed across the joists, against the other side of the
line. This second band is fixed on the alternate tops and
bottoms missed by the first band. The downside with
Fixing-band strutting, is that the joists near each opposite wall would need to be fixed firmly to the walls,
through the 50 mm packings, to offset the pulling effect
of the taut banding. Alternatively, the band could be
turned up (or down) against the wall at each end and
fixed firmly into the blockwork.
8.10.7 Horizontal Restraint Straps
Figure 8.23 30 ⫻ 5 mm restraint straps for joists parallel
or at right-angles to wall
Figure 8.23: Modern construction methods involving
lighter-weight materials in roofs and walls, has led to
the need for anchoring straps, referred to in The
412∗
8.10.8 Joists Parallel or at Right
Angles to Wall
As illustrated, the straps, which may be on top or on
the underside, require notching-in when the floor
joists run parallel to the supported wall, so as not to
clash with the seating of the flooring or ceiling
materials – but only require surface-fixing on the sides
when the joists are at right-angles to the supported
wall. The walls should be anchored to the floor joists
at centres of not more than 2 m on any wall exceeding
3 m in length, including internal load-bearing walls,
irrespective of length. When joists run parallel to the
wall to be supported, the straps should bridge across
at least three joists and have noggings and
end-packing tightly fitted and fixed between the
bridged spaces. The noggings should be at least
38 mm wide by half the depth of the joists. If the
straps are fixed on the underside, the noggings and
packing should be equal to the depth of the joists.
There should be at least four 38 mm ⫻ 8 gauge
screw-fixings in each strap.
400
400
50 mm gap to facilitate easier board fixings
1
4
3
2
Building Regulations’ Approved Document A, to restrict
the possible movement of roofs and walls likely to be
affected by wind pressure. Such straps are made from
galvanized mild-steel strip, 5 mm thick for horizontal
restraint and 2.5 mm thick for vertical restraint. The
straps are 30 mm wide and up to 1.6 m in length.
Holes are punched along the length at 15 mm staggered centres.
22 (strutting)
21
20
19
18
17
16
5
6
7
8
9
10
11
12
13
14
15
∗ This includes 12 mm expansion gap for
flooring panels
Section A–A
A
A
93
Figure 8.24 Sequence of
fixing joists
94
Fixing Floor Joists and Flooring
8.11 FITTING AND FIXING
TIMBER JOISTS
(b)
8.11.1 Procedure – Joists Built-in to
Cavity Walls
When the load-bearing walls have been built up to
storey height and allowed to set, the joists may be fitted.
After cutting to length and sealing or re-sealing the
ends with preservative, the joists – with any cambered
edges turned upwards – are then spaced out to form the
skeleton floor and temporary battens are fixed near each
end to hold the joists securely in position. The side-fixed
restraint straps are then fixed and the joists are built-in
by one course of blocks being laid all round. When set,
the notches may be cut for those restraint straps that run
across the joist tops, the 50 mm packing and the noggings cut and fixed, then the straps are screwed into
position – and the blockwork may proceed.
L type strap
(c)
Figure 8.25 (b) Restraint-type joist hanger (c) Restraintstrap position when joist has a wall-bearing
8.11.2 Sequence of Fixing Joists
Figure 8.24: Normally, the first consideration is to position the trimming joists and trimmer of any intended
opening, then, from this formation, the trimmed and
bridging joists are spaced out. Joists should be checked
for alignment with a straightedge or line and, if necessary, packed up with offcuts of thin material such as felt
DPC or oil-tempered hardboard – or lowered by minimal paring of the joist-bearing area. However, if regularized joists are used, the need for vertical adjustments
should be eliminated. Herringbone strutting is fixed
later, after the bricklayers have finished their work.
Figure 8.25: When joist hangers are to be used as an
alternative to the joists being built-into the inner skin
of blockwork, the blockwork is built to the top of the
floor-joist level and the joists are cut to length and
positioned at the same time as placing the joist
hangers. The joists must be cut carefully to the correct
length, to hold the hangers snugly against the walls,
yet not push the blockwork from its set position.
As illustrated at (a), the restraint straps are fixed to the
upper edge on the side, when the joists are at rightangles to the supported wall, or, alternatively, restrainttype joist hangers can be used (Figure 8.25(b)) where
required.
8.11.3 Procedure – Joists Bearing on
Joist Hangers
8.12 FIXING FLOORING
PANELS ON JOISTS
8.12.1 Introduction
Figure 8.25 (a) Restraint strap in relation to joist hanger
Tongue and groove (T&G) flooring panels of chipboard, plywood or Sterling OSB, machined on all four
edges with compatible tongue and groove profiles and
with laid-measure dimensions of 2400 or 2440 mm ⫻
600 mm, can be laid on suspended timber floors in the
following thicknesses related to joist-spacings: 18 mm
chipboard, 18 mm plywood and 15 mm Sterling OSB
for joists at 400 mm centres – and 22 mm chipboard,
18 mm plywood (as before) and 18 mm Sterling OSB
for joists at 600 mm centres.
Fitting and Fixing Engineered Joists
8.12.2 Fixing Procedure for
T&G Panels
Figure 8.26 Fixing T&G flooring panels
Figure 8.26: The T&G boards, as illustrated, are laid
with the long edges across the joists. The short edges
bear centrally on the joists and only the long edges
against the walls must be supported by noggings of at
least 38 mm width – but preferably of 50 mm width
and 75 mm depth. The boards should be nailed with
three or four nails to each joist, two at about 25 mm
from each edge and one or two nails equidistant
between. The nails should be 45 mm ⫻ 10 gauge
annular-ring shank type for floor thicknesses up to
18 mm and 56 mm ⫻ 10 gauge for floors of 22 mm
thickness. All joints should be glued with polyvinyl
acetate (PVA) adhesive, preferably the waterproof
type. Gluing of joints, which is often skimped, is
important to eliminate an aggravating squeaky floor.
95
Figure 8.27: These boards, as illustrated, are laid with
the long edges bearing centrally on the joists. All short
edges, including the edges against the walls, must be
supported with, preferably, 75 ⫻ 50 mm noggings
tightly fitted and fixed between the joists. As before,
the boards should be fixed with 45 mm or
56 mm ⫻ 10 gauge annular-ring shank nails at
300 mm centres around the edges and at 400–500 mm
centres on intermediate joists. Nail fixings should be
at least 9 mm in from the edge of the boards.
Cross joints on both types of board must be staggered and expansion gaps of 10–12 mm allowed around
the perimeter of walls and any abutment. Sterling OSB
square-edged panels are recommended to have a 3 mm
expansion gap between boards in addition to the
perimeter gap. Traps in the floor must be supported on
all four edges and fixed with 45 mm ⫻ 8 gauge countersunk screws. As stated on floating floors, all panels
should be conditioned by laying loosely in the area to be
floored for 24 hours before being fixed.
8.13 FITTING AND FIXING
ENGINEERED JOISTS
8.13.1 Introduction
As mentioned in the ground floor details, engineered
joists are not only used in buildings of timber frame
construction, but are now used in buildings and
dwelling houses of traditional masonry construction –
especially above ground-floor level. The details and
illustrations in this section, therefore, cover the fitting
and fixing of a Silent Floor® System of Trus Joist’s
TJI® joists at or above first-floor level.
8.12.3 Fixing Square-edged Panels
8.13.2 Main Structural Components
(a)
Figure 8.27 Fixing square-edged flooring panels
(b)
(c)
Figure 8.28 (a) TJI® joist. (b) TimberStrand™ LSL joist or
beam. (c) Parallam® PSL joist or beam
96
Fixing Floor Joists and Flooring
Figure 8.28(a)(b)(c): The three main components in
Trus Joist’s Silent Floor® System for residential buildings of masonry construction are: (a)TJI® joists – as previously described in the paragraph headed Figure
8.11(a)(b) – of varying depths and material sizes according to the floor span; (b) Timber Strand ™ LSL (laminated strand lumber), which is a manufactured
resin-bonded timber product of great strength. It is produced in wide slabs or billets and cut up into rectangular
standard sections to be used as trimming or trimmer
joists and beams or lintels for short and intermediate
spans; (c) Parallam® PSL (parallel strand lumber) is also
a manufactured resin-bonded timber product, but with
superior strength, stiffness and dimensional stability. It is
used for carrying greater loads and/or achieving greater
spans in the Silent Floor® System. Parallam® PSL is
also claimed to be aesthetically pleasing, if its natural,
laminated appearance is left exposed.
480 mm and 600 mm. The tables refer to clear spans
for uniformly loaded joists and they assume the provision of a 22 mm chipboard floor and a directly-applied
plasterboard-type ceiling for joists spaced at 600 mm –
and a 18 mm chipboard floor and a similar ceiling for
joists spaced at 300 mm, 400 mm and 480 mm. Apart
from the Guide information, the Trus Joist company
offer technical support to specifiers and builders
throughout the UK and Ireland. This includes training in the provision of specification and installation.
Also, leading-edge automation tools are available and
include: TJ-Beam® software, which produces singlemember sizing options in floors, and TJ-Xpert® software, which automatically tracks loads throughout the
structure and develops sizing solutions, material lists,
framing plans and installation details.
8.13.5 Typical Upper-floor Layout
8.13.3 TJI® Standard Sections
(F)
(a)
(G)
(d)
(b)
(e)
Depth
(c)
(E)
(a)
(b)
(c)
(d)
Figure 8.29 (a) Series 150 joist; (b) Series 250 joist;
(c) Series 350 joist; (d) Series 550 joist
Figure 8.30 Typical upper-floor layout, indicating the
various Trus Joist framing arrangements, (a) to (e), detailed
in Figure 8.31
Figure 8.29(a)(b)(c)(d): The standard TJI® joist sections available in the Silent Floor® System are: (a)
Series reference number 150, with a 9.5 mm web
thickness, 38 ⫻ 38 mm top and bottom flanges and a
depth (height) of 241 mm or 302 mm; (b) Series number 250, with a 9.5 mm web, 45 mm wide ⫻ 38 mm
deep flanges and a depth of 200 mm, 241 mm,
302 mm, 356 mm or 406 mm; (c) Series 350, again
with a 9.5 mm web, but top and bottom flanges of
58 mm width ⫻ 38 mm depth and with joist-depths
equal to Series 250; (d) Series 550, with a 11.1 mm
web, 89 mm wide ⫻ 38 mm deep flanges and joistdepths equal to Series 250 and 350.
Figure 8.30: The illustration shows a simple, yet typical upper-floor layout of TJI® joists bridging across
the shortest span, either bearing on the inner-skin
block wall or, alternatively, bearing on joist hangers
with their top flanges bearing on the block wall. A
stairwell opening is shown typically against a structural wall, but may of course be anywhere in the mid
area; the main point being that the opening creates a
transference of load to the joist marked (E), which in
turn will transfer the imposed load to the joists
marked (F) and (G). Traditionally, joist (E) would be
referred to as a trimmer joist and joists (F) and (G) as
trimming joists. The short bridging joists would be
referred to as trimmed joists. In Trus Joist’s Silent
Floor® System, the components shown here acting as
trimmer and trimming joists would be either
TimberStrand™ LSL or Parallam® PSL beams.
Alternatively, as illustrated at (e) in the framing details
in Figure 8.31, TJI® joists may be joined together to
carry an additional load. Finally, Trus Joist’s Guide
8.13.4 Joist-size, Span and Spacing
Trus Joist’s Technical Guide notes for the UK and
Ireland contain span tables giving joist-size and joistspacing related to spans for residential applications.
The spacing centres used are 300 mm, 400 mm,
Fitting and Fixing Engineered Joists
(a)
(b)
(d)
97
(c)
(e)
notes state that herringbone strutting (referred to by
them as bridging) or solid strutting (mid-span blocking) is not required, but may enhance the floor’s performance if properly installed.
8.13.6 Framing Details
Figure 8.31(a)(b)(c)(d)(e): Although Trus Joist’s Guide
notes show a wide range of framing details, the five
examples given here only represent those that could be
used in the typical upper-floor layout illustrated in
Figure 8.30. Detail (a) shows TJI® joists bearing on
the inner-skin blocks of an external cavity wall; (b)
shows a TJI® joist supported by a Simpson’s JHMI
single-sized joist-hanger. Note that timber webstiffeners will be needed with these joist hangers to
eliminate lateral movement at the top of the web,
within the hanger, and to enable the hangers to be
fixed through their side holes. Also, joists supported
by hangers built into walls, should have at least
675 mm of cured (set) masonry built above the hangers’
flanges before the floor has any construction materials
(loads) placed upon it; (c) shows a TimberStrand™
LSL trimmer beam to trimming beam arrangement,
supported by a Simpson’s WPI timber-to-timber topflange joist hanger; (d) shows a TJI® joist supported
by a TimberStrand™ LSL trimmer beam, via a
Simpson’s ITT timber-to-timber, single-sized joist
hanger; (e) shows a TJI® joist to a double TJI® joist
trimmer beam arrangement using – as in the framing
detail at (d) – an ITT timber-to-timber hanger. Note
that there are side lugs on the ITT hangers that must
Figure 8.31 (a–e) Trus Joist
framing details
be bent over and nailed to the top edges of the bottom
flanges with 3.75 ⫻ 38 mm nails.
8.13.7 Restraint Strap Details
Restraint strap
Noggings and wall-packing
Figure 8.32 Restraint strap slotted through TJI® webs
Figure 8.32: The need for restraint straps and their
legal requirement and application to floors above
ground-floor level, is covered in detail under section
8.10.7 (Horizontal Restraint Straps) of this chapter.
However, as illustrated, when TJI® joists are parallel to
the structural wall, the straps cannot be notched-in to
the flanges (as is the practice with solid timber joists)
and need to be inserted through slots cut in the webs,
38 mm wide ⫻ strap-thickness ⫹ tolerance deep. The
slots should be close to the underside of the top
flanges, with not less than 3 mm of web remaining.
The 38 mm ⫻ half joist-depth noggings and the timber wall-packing should be of C16 structurally graded
timber. The Trus Joist Guide notes do not show a
detail of wall restraint when the TJI® joists are at right
angles to the wall (this may be in their software), but it
seems feasible to either fix them to the vertical face of
the top or bottom flanges, or stiffen-up the web thickness with plywood or OSB and fix the straps to the top
98
Fixing Floor Joists and Flooring
or bottom area of the web. Finally, note that the Trus
Joist details indicate a minimum 25 mm gap between
the wall and the TJI® joist parallel to it.
Two 38 ⫻ 125 mm solid struts each end
8.13.8 Perimeter Noggings
Where the TJI® joists are at right angles to a structural wall, noggings are fitted between the joists and
against the wall and are skew-nailed with 65 mm or
75 mm round-head wire nails. Note that these
perimeter noggings provide lateral restraint when the
joists are on hangers, but otherwise are only needed
when using sheet decking material such as chipboard,
OSB or plywood, to provide edge-support; they can
be omitted when using ex 25 mm (20 to 21 mm finish)
T&G boarding for decking, providing the joists are
built-in to the wall. However, noggings can be used
solely to achieve lateral joist-support and positional
spacing. This could particularly improve the working
stability of a joisted-layout, seated on block walls,
waiting to be built-in. Because skew-nailing would be
impractical in this situation, Simpson’s Z35N clips
could be used. Noggings are usually of sawn finish and
may be cut from timber sizes of 38 ⫻ 50 mm,
50 ⫻ 50 mm, or 50 ⫻ 75 mm.
8.13.9 Permissible Holes in
Joists and Beams
Round holes and square or rectangular holes can be
drilled or cut into the webs of TJI® joists, but only in
specific places and of certain sizes as specified in Trus
Joist’s Hole Charts (too detailed to reproduce here).
The holes may be drilled or cut anywhere vertically in
the webs, but not less than 3 mm of web must be left
at the top and/or bottom – and joist-flanges must not
be cut at all. Note that TJI® joists are manufactured
with 38 mm Ø perforated knockout holes in the web,
at approximately 300 mm centres along the joist’s
length. These do not affect other holes that may be
required, providing they conform to the charts’ criteria. Rectangular or square holes are not allowed in
uniformly loaded beams comprised of
TimberStrand™ LSL or Parallam® PSL.
Furthermore, round holes above 50 mm Ø are not
allowed – and holes that may be drilled at or below
this diameter must conform to the chart’s criterion
regarding position. Finally, note that cuts or notches
are not allowed in the bottom or top edges (chords) of
beams, or in the bottom or top flanges of TJI® joists.
8.13.10 Safety Bracing
Figure 8.33: For safety’s sake, it must be realized that
newly-joisted floors are unstable until all the end
Diagonally braced anchorage area
Figure 8.33 Safety bracing to newly-joisted TJI® floor
bearings are complete and the ‘green’ masonry alongside built-in joists or above built-in joist-hangers has
cured (set). Workers must not be allowed to walk on
the joists, and construction loads must not be laid on
the joists, until longitudinal safety bracing (with a recommended minimum 19 ⫻ 89 mm section) is
attached to the tops of joists, as illustrated. Also, at
least two 38 ⫻ 125 mm timber blocks – like solid
strutting – must be fixed at each opposite end of the
layout (two blocks each end), between the webs of the
joists, to create an anchorage area of lateral restraint.
The top bracing battens, starting from above the completed anchorage-area, are recommended to be fixed at
every joist with two 3.35 ⫻ 65 mm nails (left with
their heads protruding). Longitudinal bracing should
be positioned near the bearings and in mid-positions
between 1.5 mm and 2.4 mm, according to the Series’
number of the TJI® joists used. Safety bracing should
only be removed at the decking stage, progressively as
the decking is laid – not all at once.
8.14 POSI-JOIST™ STEEL-WEB
SYSTEM
8.14.1 Introduction
This section covers the fitting and fixing of the PosiJoist™ system of engineered floor-joists at or above
first-floor level (although they can also be used at
ground-floor level, if in compliance with Part C of the
Building Regulations, as described in section 8.2.2
(Regulation Requirements) of this chapter). Although
Posi-Joists are also used as roof components and in
Post-JoistTM Steel-web System
buildings using a structural inner-skin of timber-frame
construction, the references here are only intended for
floors in dwelling houses of masonry construction.
Furthermore, general floor-joisting principles and other
details – including safety bracing – already covered in
this chapter, will not be repeated here.
99
8.14.3 Typical Floor Spans
Joist
reference
Spacings
400
PS8
600
8.14.2 Component Details and
Advantages
400
PS9
600
400
PS10
600
400
PS210
600
TR26
Flange size
Max span
72 ⫻ 47
5.100
97 ⫻ 47
5.560
72 ⫻ 47
4.310
97 ⫻ 47
4.720
72 ⫻ 47
5.220
97 ⫻ 47
5.710
72 ⫻ 47
4.330
97 ⫻ 47
4.730
72 ⫻ 47
5.980
97 ⫻ 47
6.550
72 ⫻ 47
4.760
97 ⫻ 47
5.520
72 ⫻ 47
6.920
97 ⫻ 47
7.800
72 ⫻ 47
5.550
97 ⫻ 47
6.640
Figure 8.35 Floor spans over bearings
Figure 8.34 Part view of a typical Posi-Joist
Figure 8.34: Posi-Joists are a combination of stressgraded structural timber flanges, joined by the MiTek
Posi-Strut™ galvanized-steel web system. The
timber flanges for the different-depths of standard
joists, vary only in width. The depth of the flanges is
consistent at 47 mm finish. The width is either 72 mm
or 97 mm finish, determined by joist-spacing related
to span. There are four standard Posi-Joist™ depths,
which are referenced by a PS (Posi-Strut) number.
PS8 ⫽ 202 mm deep, PS9 ⫽ 223 mm, PS10 ⫽
254 mm, and PS210 ⫽ 302 mm deep. An overview of
how these referenced joist-depths relate to span, is
shown in MiTek’s chart reproduced at Figure 8.35.
These relatively lightweight, easily manageable
joists’ main advantage is their unique open-web
design, which allows electrical cables, plumbing pipes
and venting ducts to be laid quickly underfloor in any
direction. Other benefits include achieving greater
spans without the need for intermediate load-bearing
walls (note that if the span exceeds 4 m, a strong-back
is installed at mid-span, as shown here in the separate,
illustrated details); even over long spans, no herringbone strutting is required; Posi-Joists can be ordered
with solid-block trimmable ends, for on-site reductions of up to 150 mm each end.
Figure 8.35: As mentioned above, MiTek’s chart of
Typical Floor Spans is a simple overview of spans
measured over bearings, which will give an indication
of the particular joists required. Full load and clearly
detailed information is available from local PosiJoist™ manufacturers or from MiTek Industries.
8.14.4 Posi-Joist™ Trim-It™ Floors
600 mm
Figure 8.36 Trim-It joist with 600 mm solid trimmable end
Figure 8.36: Another innovative engineered floor-system pioneered by MiTek®, is the Posi-Joist™ TrimIt™ floor, with all the advantages of its open-web
configuration and a unique solid-end insert allowing
up to 600 mm to be trimmed on site from one end of
each joist – if necessary. This system offers a range of
five spans at a joist-depth of 253 mm, for standard
floor loads. The available spans are 3.3 m, 3.9 mm,
4.5 m, 5.1 m and 5.7 m. Bearing in mind that each
joist-span has the capability of multiple reductions of
the 600 mm Trim-It end, the range of possible spans
100
Fixing Floor Joists and Flooring
available from the stocked range of five, runs into high
double figures.
8.14.5 Posi-Joist™ Standard Details
∗
∗
(a)
(a)
(b)
Figure 8.37 (a) Bottom-chord bearing; (b) top-chord
bearing
* Posi-web must be 15 mm minimum over the bearing
Figure 8.37(a)(b): One of the prime considerations of
any joist-arrangement is the wall-bearing detail. The
first option shown above is referred to in MiTek’s literature as a bottom-chord bearing into masonry (the
inner-skin (blockwork) of a cavity wall). As illustrated,
this is where the square end of the Posi-Joist™ is
seated on the wall, flush to the rear face of the blockwork, and built-in at the sides and above. The second
option above is referred to as a top-chord bearing. The
top chord (flange) only is seated on the wall and builtin and the bottom chord (flange) butts up against a
continuous 47 ⫻ 72 mm so-called ledger fixed to the
wall. The end of the chord should touch the ledger,
but is allowed a maximum gap of 6 mm. The metal
Posi-web, as illustrated, must overrun the wall-bearing
by at least 15 mm.
(b)
Figure 8.38 (a) Posi-Joists bearing on wall hangers with
47 ⫻ 72 mm noggings between top chords; (b) special
notched ends of Posi-Joists to allow a continuous
47 ⫻ 72 mm restraint ledger to be inserted
8.14.7 Staircase Openings
Figure 8.39(a): The stair-opening shown below uses
so-called 2-ply joists as trimming joists. These are
formed on site by fixing two Posi-Joists together with
the aid of Cullen UZ47 clips, or similar, as specified
by the design. The single Posi-Joist™ shown here,
attached to the trimming joists with Simpson LBV or
Cullen OWF/OWT hangers, is acting as a trimmer
joist, carrying the trimmed joists. If carrying above a
certain number of trimmed joists, it too might have to
be of 2-ply construction. The trimmed joists are
attached to the trimmer with similar hangers. Note
that the bottom flanges of all hangers need to be
notched into the Posi-Joists.
Cullen UZ47 clips
8.14.6 Joist Hanger to Inner
Cavity-wall
Figure 8.38(a)(b): The third and fourth wall-bearing
options are shown above. As illustrated, the ends of
the Posi-Joists bear into wall hangers, which are fixed
to the joists with 3.75 ⫻ 32 mm galvanized plasterboard nails. The choice of hanger and minimum bearing is determined by the floor-design, the load, the
joist-width (72 or 97 mm) and the blockwork level for
the hanger’s bearing flange. Option (a) above, has
47 ⫻ 72 mm restraint-noggings fixed between the
top chords, but option (b) shows the advantage
(by being more easily fixed) of a continuous restraint
ledger, facilitated by the manufacturer’s special
end-blocking.
Stairwell
area
(a)
Figure 8.39 (a) Posi-Joist arrangement around stairwell
Overlay Flooring
101
∗
(b)
(c)
Figure 8.39 (b) 2-ply trimming joist with solid trimmer on
joist hanger; (c) sectional view through solid trimmer
showing trimmed joist bearing upon it.
* Note that Posi-web must be 15 mm minimum over the
bearing
Figure 8.39(b)(c): An alternative stair-opening
detailed above uses similar 2-ply trimming joists, but
solid timber or LVL (laminated, engineered timber) as
a trimmer joist. The trimmer is fixed to similar
Simpson or Cullen joist hangers, but the lowered, top
surface of this trimmer acts as a bearing for the top
chords of the trimmed joists nailed to it. The bottom
chords should butt up against the trimmer. Note that
the metal Posi-web must overrun the trimmer-bearing
by at least 15 mm and, as before, the bottom flanges of
the hangers need to be notched into the trimmer joist.
8.14.8 Horizontal Wall-Restraint
As covered already in this chapter, where horizontal
wall-restraint is needed to meet the requirements of
The Building Regulations’ Approved Document A, horizontal restraint straps are fixed. When Posi-Joists are
parallel to the wall, the straps can be hooked through
the blockwork and fixed to the side of a timber plate
fixed across the topside of the bottom chords, at rightangles to the wall. The plate should be of at least
35 ⫻ 97 mm section and of Class C16 timber, twice
fixed to each of three joists with 3.1 ⫻ 75 mm galvanized wire nails. The strap should be fixed with a minimum of four No 8 gauge ⫻ 1--12 ⬙ (4.0 ⫻ 38 mm)
screws, one at each end and others equidistant
between. If restraint straps are required when PosiJoists are at right-angles to a wall, they can be screwed
to the side-edges of the joists’ flanges.
Figure 8.40 Sectional view of a 35 ⫻ 150 mm
‘strongback’ fixed to a vertical block
to the joists, twice nailed to 38 ⫻ 75 mm blocks. The
blocks are also twice nailed to the top and bottom
chords. The nails used are 3.1 ⫻ 75 mm galvanized
wires. As illustrated, the strongback must be kept tight
to the underside of the top chord. Note that some
strongbacks are fixed to built-in soldier pieces formed
within the webs, according to the span and design.
8.15 OVERLAY FLOORING
8.15.1 Introduction
Overlay floors of hardwood, or laminate flooring with
a hardwood effect, are very popular nowadays.
However, hardwood floors and overlay floors are not
new. Wide, square-edged oak boards were used centuries ago in certain properties and hardwood-strip
floors, in the form of narrow strips of T&G boarding,
about 60 mm wide, have been used for overlaying subfloors for many decades. Traditionally, they were
mostly ‘secretly nailed’ through the inner-edges of the
tongues, whereas nowadays they are more likely to be
glued together and laid as a ‘floating floor.’ Thin
plastic-laminate floors – with no alternative other
than being laid to float – use self-locking click joints
without glue. Today’s demand for hardwood floors is
no doubt because more people can afford them – and
the popularity of laminate flooring perhaps indicates
those who have to (or choose to) compromise.
8.15.2 Hardwood Strip Flooring
(a)
(b)
8.14.9 Strongbacks
Figure 8.40: If the joist-span exceeds 4.0 m, a strongback
strut is required in mid-span to stiffen the floor. If more
than one strongback is required, they should be fixed at
a maximum 4.0 m centres. The size, detail and position
of strongbacks, is usually specified by the manufacturer.
The illustration above shows the simplest of the strongbacks running through the open webs at right-angles
(c)
Figure 8.41 (a) T&G hardwood strip flooring for secretnailing technique; (b) T&G hardwood strip for floating floor;
(c) hardwood veneered, ply-laminate panel for floating floor
102
Fixing Floor Joists and Flooring
Figure 8.41 (a): If hardwood strip floors are to be
nailed, the tongue and groove detail should be as illustrated, with a sloping tongue and an offset shoulder to
facilitate and accommodate secret-nailing. By this
method, lost-head nails (of 65 mm length) are drivenin at 45⬚ angles, at maximum 600 mm centres. These
angles and the final punching in of the nails, effectively cramps up each strip as the floor proceeds.
Alternatively, the boards can be fixed more speedily
with an angled brad-nailer gun, such as the Paslode
Impulse IM65A (covered in chapter 2), or with a
semi-automatic flooring-nailer, such as the Primatech,
that drives in so-called ‘L Cleats’ at 45⬚ angles.
Figure 8.41(b): The standard T&G profile illustrated
here, lends itself to being glued and cramped together
when laid as a floating floor. It can be secretly nailed
without being glued, but splitting and bulging of the
tongue and lower edge is almost unavoidable in places.
If this occurs, the holding-power of the fixing is
impaired and the next row of boards might not cramp
up effectively, leaving unsightly gaps on view. The
header joint used for both types of tongue-and-groove
board, should be square and neatly butted. They must
be strategically placed to avoid closeness to each other
and no header joint in any following row should be
closer than 300 mm to any header joint in the preceding row. When being glued, it is only necessary to run a
small bead of PVA adhesive – from a squeezable plastic
container – along and within the groove. Although
cramping will slow down the job, it is necessary to
cramp each board for a short period of time, until the
glue reaches an initial-set stage – which might be only a
few minutes. Adjustable-strap type cramps are available
for this, or a traditional wedging technique can be used.
Figure 8.41(c): The third type of hardwood floor
consists of interlocking, laminated floor panels made
of real wood plies (plywood). The core plies are of
softwood and the surface ply – or veneer – is of hardwood, about 3 mm thick. Typical panel sizes are
145 mm wide ⫻ 1220 mm long ⫻ 13.5 mm thick. The
panels are laid as a floating floor and they have the
advantage of glueless, self-locking click joints on all
four edges. Also, by being an engineered-timber product, they retain the benefits of natural wood, without
the inherent weaknesses of twisting, cupping, shrinking or splitting. As before, the header joints must be
staggered. Ideally, half a panel’s length should start the
second row, but this rarely works out in practice.
Figure 8.42: Plastic-laminate flooring – usually just
referred to as laminate flooring – is comprised of a
hard-wearing, wood-grain-patterned plastic membrane
on the face-side, which has been fused (under great
heat and pressure) to a high-density fibreboard (HDF)
core of 7 to 8 mm thickness. The panels are about
150 mm longer and 50 mm wider than the engineeredtimber panels described above and each panel usually
displays a three-row, strip-floor effect. This type of
flooring is produced to varying grades to suit different
levels of use, and can only be laid as a floating floor. In
recent years, these panels had standard T&G joints
that were glued together, but they now have glueless,
self-locking click joints on all four edges.
8.15.4 General Considerations
The following points apply to either fixed or floating
overlay-floors:
●
●
●
●
●
8.15.3 Hardwood-effect Laminate
Flooring
●
Figure 8.42 Plastic-laminate floating-floor panel
Follow the manufacturer’s instructions regarding
floor preparation and the types of underlay
required. If not familiar with floor-laying techniques, study the excellent detailed illustrations
usually supplied by the manufacturers.
Consider in what direction the boards should run.
Running in the direction of the longest wall will
reduce end cuts, but often the visual effect is
improved if boards run in a forward direction from
an entrance doorway.
Once the direction is determined, it is wise to divide
the length of the room by the precise widthmeasurement of a board or panel, to find out how it
will meet the other side. Often it is discovered that a
very narrow, awkward rip will be required. If so, create a better balance by reducing the width of the first
row laid. In a more complex situation, forethought
should also apply to any projecting or receding
walls that might be met before the far side is
reached – as in, for example, an L-shaped room.
When calculating, take the required expansion gaps
into account.
By using temporary plastic or wooden folding
wedges, always establish an expansion gap of
approximately 12 mm between the edges of hardwood flooring and the perimeter of the room – and
10 mm in the case of plastic-laminate flooring.
Additionally, in large rooms, expansion joints will
be needed within the visual area of the floor when
the length or breadth of a room is in excess of 10
linear metres. If required, plan these joints strategically to be symmetrical or obscure within the room.
Cover the joint-gaps with co-ordinating T Bars.
Floating floors are held down by the perimeter skirting, which – if necessary – should be carefully
scribed to the floor. If skirting boards already exist in
Overlay Flooring
●
a room, remove them to achieve a professional finish
and re-fix or renew them afterwards. Alternative
skirting beads or quadrants always look amateurish.
Floors should always fit under door-linings, frames
and architraves, etc. To achieve this, lay an offcut
piece of flooring face down against the architrave,
etc, and run a fine handsaw against it to remove the
obstruction. Keep the saw pressed down flat whilst
sawing, by applying light finger pressure from your
idle hand onto the blade and flexing the saw slightly.
●
103
When a hole is drilled near the edge of a laminate
panel to accommodate a radiator pipe, to remove
the back-piece (and be able to reuse it), make two
V-shaped cuts towards the hole with a fine saw
(gent’s saw or tenon saw) at 45⬚ in plan – and at
about 60⬚ vertically, leaving only a semi-circle in
the board when the back-piece is removed. When
the panel is in position, the twice V-shaped backpiece can be glued in flush to the surface.
9
Fixing Interior and Exterior
Timber Grounds
9.1 INTRODUCTION
slightly less thick than the required plaster
thickness.
Timber grounds are either sawn or prepared battens,
fixed to walls or steel sections, to create a true and/or
receptive fixing surface. Depending on the material
the grounds are to be attached to, they may be fired
onto steel flanges or webs, brickwork and concrete
with a cartridge powered tool, fixed to lightweight
aerated blocks with screws and plugs, or fixed to
blockwork and brickwork with Fischer type
Hammer-fix screws.
9.2 SKIRTING GROUNDS
50 ⫻ 13 mm
sawn ground
Cut, clasp nail
fixings to par
grounds
Ex. 75 ⫻ 19 mm
skirting
Figure 9.1 (a) Skirting grounds
Figure 9.1(a): Although grounds were traditionally
only used on good class work to promote truer plastered surfaces and provide a means of fixing for the
skirting, they are included here because research has
shown that a small percentage of dwellings being
built still use wet-plastering techniques and therefore
may use grounds. The grounds are bevelled on their
top edge to retain the bottom edge of the plaster and
must, of course, be equal to the required plaster thickness. As packing pieces (off-cuts of damp-proof
course material and plastic shims are ideal) are often
required on uneven walls, the grounds should be
9.2.1 Fixing Technique
Wall
Ground
Line
Movable
gauge
block
Figure 9.1 (b) Checking straightness of ground with
stringline and gauge blocks
Figure 9.1(b): The top of the grounds should be
levelled (or parallel to the finished floor) and set up to
finish between 6 and 10 mm below the anticipated
skirting height. Long grounds should be fixed at each
end and have a string line pulled taut along the face.
Two pieces of offcut ground, one at each end, are
pushed in between the line and ground, while a third
piece of offcut ground is tried between the taut line
and the unfixed ground at 600–900 mm intervals,
packed if necessary and fixed. Shorter grounds may be
checked for straightness with a timber or aluminium
straightedge. Internal and external angles are butt
jointed – not mitred. On external angles, run the first
ground about 50 mm past the corner, butt the end of
the second ground up to this and when fixed, cut off
the first projection flush to the second ground’s face.
9.2.2 Deep and Built-up Skirtings
Figure 9.1(c): Grounds for deep or built-up skirtings
may be required on refurbishment, maintenance and
repair work. Such grounds, as illustrated, have a
longitudinal top ground and vertical, face-plumbed
soldier pieces of ground fixed at 600–900 mm centres.
Depending upon the particular skirting design and
height, additional stepped soldiers may be required to
be fixed onto the first row.
Wall-panelling Grounds
105
Trimmed
floor
Soldier pieces
for deep skirtings
Stepped soldiers for
built-up skirtings
Figure 9.1 (c) Soldier pieces for deep skirtings and
stepped soldiers for built-up skirtings
Grounds to
apron lining
Figure 9.3 Grounds to apron lining
9.3 ARCHITRAVE GROUNDS
plywood apron lining, or in the form of vertical
soldier pieces if a timber lining is being used. The
soldier pieces give better support by being across the
grain to offset any cupping of the lining.
9.5 WALL-PANELLING
GROUNDS
Architrave
grounds
Figure 9.2 Architrave grounds
Figure 9.2: Because the modern architrave section is
relatively narrow, the traditional use of grounds in
these situations is rarely required nowadays. Similar to
skirting grounds, the edge against the plaster was
bevelled and had to be concealed under the outerarchitrave edge by about 6–10 mm. These grounds
helped to keep the wet plaster away from the lining’s
edges and provided a true and receptive fixing surface
for the outer-architrave edges.
9.4 APRON-LINING GROUNDS
Figure 9.3: Grounds are often required behind the
apron lining around the edge of a trimmed stairwell.
This is to bring the face of the lining to a position
equal to the centre of the newel post and to further
support the projecting landing-nosing. The grounds
may be longitudinal if being faced with an MDF or
Figure 9.4 Horizontal cladding secret-nailed to vertical
grounds
Figure 9.4: Grounds – without bevelled edges and sized
about 50 ⫻ 25 mm – may be fixed horizontally across a
wall and spaced at 600 mm centres from floor to ceiling,
acting as a straight and plumb fixing medium for vertical boarding. Alternatively they may be fixed vertically
at similar centres across the wall, acting again as a true
surface and fixing medium for horizontal boarding. The
technique in these situations is, having fixed two
extreme grounds straight and true (one horizontally
near the floor, one near the ceiling – or one vertically on
the extreme left, one on the extreme right), they are
106
Fixing Interior and Exterior Timber Grounds
used as a fixed datum for all the in between grounds to
relate to, by means of a straightedge or string line.
9.6 FRAMED GROUNDS
Figure 9.5: Occasionally, on traditional forms of wall
panelling, framed grounds are still used. Basically,
these consist of either an arrangement of grooved
uprights and tongued cross-rails of about 50 ⫻ 25 mm
section, or morticed uprights and stub-tenoned
cross-rails of a similar section. The fixing technique
for framed grounds is as explained above for wallpanelling grounds.
9.7 EXTERNAL GROUNDS
Fixing timber grounds for external work such as for
timber or plastic cladding will again involve a fixing
technique similar to that described above for wallpanelling grounds. The main difference will be that
the grounds should be tanalized or protimized, or
protected with a similar acceptable preservative
treatment.
Figure 9.5 Framed grounds
10
Fixing Stairs and
Balustrades
10.1 INTRODUCTION
Figure 10.1: Traditionally, a series or flight of steps,
rising from one level to another, whether it be a floor
to a landing or vice versa, was known as a stair, but is
now more commonly referred to as stairs or a staircase.
Originally, stairs was the plural of stair, meaning more
than one flight of steps and the word staircase meant
the space within which a stair was built. This space is
now called a stair well. These more-recent, modern
terms are used here.
10.1.1 Manoeuvrability
For reasons of easier transportation, manoeuvrability
through doorways, and practical issues involved in the
fitting and fixing, staircases usually arrive on site separated from the newel posts and balustrade, the bottom
step (if such protrudes beyond the newel post, as with
a bullnose step), the top riser board, the landing nosings and the apron linings.
10.1.2 When to Fix
Fixing is best done before dry lining or traditional plastering takes place, soon after the shell of the building is
formed and the roof completed. This sequence allows
the staircase to be fixed to the bare wall, so ensuring a
better finish by the plasterer or dry lining being seated
on the edges of the wall-string board, sealing any gaps
that otherwise would appear if the stair-string were
fixed to the dry-lined or plastered surface.
Handrail
Landing nosing
Balustrade
Tread
Traditional
handrail
Traditional
balusters
(see (b))
Outer string
Turned
baluster
or spindle
Storey
newel post
Wall or
inner string
Riser
Bullnose
step
(a)
Figure 10.1 Stair terminology
Newel post
Spandrel enclosure
(b)
108
Fixing Stairs and Balustrades
10.1.3 Other Considerations
Fixing at this stage also effectively reduces the disproportionately thick-edge appearance of the wall string
and, if worked out, perhaps by packing the wall string
when fixing, it can be gauged so that the remaining
thickness of wall string equals the thickness of the
skirting board that will eventually abut its ends at the
top and bottom of the staircase. This is an important
point on good quality work, because abutting skirting
boards ought to be flush with the string-face.
Another reason for installation at this stage is to allow
building operatives quick and easy access to the upper
floor(s). The following steps outline the operations
involved in fitting and fixing a straight flight of stairs.
Check and establish
finished floor levels
10.2 INSTALLATION
PROCEDURE
10.2.1 Checking Floor Levels
(a)
Figure 10.2(a): Check whether the existing floors
(upper and lower) are finished levels. In the case of a
boarded or ply/chipboard/OSB sheeted floor, these are
usually the levels to work to – as any additional floor
covering can be assumed to cover the steps as well,
thereby retaining equal rises to all steps. If, however,
the ground floor is of concrete (slab form or beams and
blocks) and has yet to receive a finishing material such
as a 50 mm sand-and-cement screed, or a floating floor
of polystyrene sheets ( Jablite) and tongued and
grooved chipboard panels, or sand/cement screed and
wood parquet blocks, then the finished floor level (ffl)
must be known or found out and established – and
packing blocks prepared to fit under the bottom step.
Bench mark established
above site datum
1m
Bench mark
ffl
(b)
10.2.2 Establishing the Finished
Floor Level
Figure 10.2(b): At this stage of the job, the ffl has
usually been established and may be found, ready to
transfer from the bottom of door linings or the sills of
external door frames. Alternatively, a bench mark
above the site datum can be levelled across to the stair
area, marked on the wall and measured down the set
amount to the ffl (as outlined in the chapter on Site
Levelling and Setting Out).
10.2.3 Cutting for Floor and
Skirting Abutment
Figure 10.2(c): Next, cut the wall string at the bottom
to fit the ffl (even if the finished floor is yet to be laid).
Figure 10.2 (a) Establish finished floor levels
(b) Establish bench mark
If not already cut or marked during manufacture, then
simply measure down the depth-of-rise from the top
of the first tread-housing (if such exists, as in the case
of a bottom step left out for site-fixing), or measure
down from the tread and mark a line through this
point at right-angles to the face of the first riser-housing or riser board. Cut carefully on the waste side with
a sharp saw (to produce a clean cut). Then mark the
plumb cut to form the abutment joint between the
string and skirting board, as indicated. To do this, set
the skirting height, say 95 mm, on the blade of the
combination mitre-square and square-up from the ffl
Installation Procedure
109
95
ffl
Cut off to skirting height
Cut off to
floor
level
Figure 10.2 (c) Wall-string cuts at
bottom
(c)
cut, sliding along until the corner of the blade touches
the edge of the string. At this point, mark the plumb
line and cut with a panel or fine hardpoint saw.
10.2.5 Offering Up and Checking
Newel post in
temporary position
1
4
95
Skirting
height
2
Check shoulder-fit
3
Inner (wall)
string
4
1
Spirit
Skirting
plumb – cut = cL
4
of trimmer
below
3
level
10.2.4 Cutting to Fit Trimmer and
Skirting Abutment
2
Outer string
(d)
Figure 10.2 (d) Wall-string cuts at top
Figure 10.3 Checking for error in total rise
Figure 10.2(d): At the top end of the wall string, more
elaborate marking out and cutting is required to
enable the staircase to fit against the landing/floor
trimmer or trimming joist. This also includes preparation of the string to meet the skirting. As indicated,
the cuts are made in four places:
1. within the riser housing, on a line equal to the back
of the riser;
2. within the tread housing, on a line equal to the
underside of the flooring;
3. on a plumb line equal approximately to the centre
of the landing trimmer (this is for the skirting
abutment);
4. a horizontal cut at the very top of the string, equal
to the skirting height.
This last cut should be planed to a smooth finish, as it
becomes a visual edge of the string margin.
Figure 10.3: Now offer the staircase up into position,
resting against the landing and packed up at the bottom, if necessary. Check the treads across the width
and depth with a spirit level. Any inaccuracies registering in the depth of the tread will infer that either a
fundamental error has been made in the mathematical
division of the total rise of the staircase, or that the
floor-to-floor storey height is not what it should be.
A more positive way of confirming this will be to
position the bottom newel post temporarily onto the
outer-string tenons, making sure that the shoulder of
the bare-faced tenon fits snugly against the newel, and
checking for plumb with the spirit level, as illustrated.
10.2.6 Dealing with Inaccuracies
If inaccuracies are confirmed and they are only minor,
they may have to be suffered, as very little can be
110
Fixing Stairs and Balustrades
10.2.7 Fixing the Wall String
built of aerated lightweight material such as Celcon or
Thermalite blocks, then nailing with 100 mm cut
clasp nails will be satisfactory. These fixings are driven
through the string on the underside of the treads,
within the triangular area of every third or fourth step.
However, if the wall is built with bricks or concrete
blocks, and is not receptive to direct nailing, the wall
string/wall will have to be drilled through in one
operation to receive Fischer-type nylon-sleeved
Frame-fix or Hammer-fix screws of 100 mm length.
These may also be used, of course, if the firstmentioned aerated light-weight blocks do not prove
to be dense enough to grip the cut clasp nail.
Figure 10.4: After minor adjustments, if any, to the
normal correctly fitting staircase, the next operation to
consider is the fixing of the inner string to the wall. If
the wall, being the inner-skin of cavity construction, is
10.2.8 Preparing the Bottom
Newel Post
done – short of shoddy tactics such as adjusting the
shoulder of the string-tenons to improve the plumb
appearance of the newel posts. If inaccuracies in level
and plumb are more serious, then measure the rise of
one step carefully, multiply it by the total number of
steps in the staircase and compare this figure with the
actual measurement of the storey height from ffl
below to ffl above. Armed with this information, it
would be wise to confer with the site foreman or
builder’s agent before proceeding.
Cut
clasp
nails
Figure 10.4 Fixing the wall string
or
Frame-fix/
Hammer-fix
screws
Figure 10.5: Having decided on the method best
suited to fixing the wall string, the next job is to prepare the bottom newel post to meet the floor level.
The post is usually left longer at its lower end to allow
for site treatment in various ways, according to the
construction of the floor. Unless specified, the carpenter will decide exactly which way is suitable for a particular floor. The various methods of treatment at floor
level are now described.
Newel Rests on Concrete
Figure 10.5(a): On concrete floors (slab form or beams
and blocks), the newel post can be cut to rest on the
concrete – although the end should be sealed with
Newel post
Sand and cement
floor screed
ffl
Bullnose
step
Concrete
oversite
Figure 10.5 (a) Screed
bedded around newel
Installation Procedure
111
preservative and/or wrapped with a piece of polythene
sheet. When, after installation of the staircase, the
sand-and-cement floor screed is bedded and set around
the post, a further degree of rigidity is achieved.
Secure with Metal Dowel
ffl
ffl
Figure 10.5 (c) Newel post housed into floor
Figure 10.5 (b) Screed bedded around metal dowel
Figure 10.5(b): Alternatively, as illustrated, the newel
post can be cut off at floor level, be drilled up into the
end grain and have a metal dowel inserted. The dowel,
which can be cut from 18 mm diameter galvanized
pipe, should be inserted for at least half its length and
protrude to rest on the concrete. Separate, localized
bedding, with a strong mix of sand and cement
around the dowel, is recommended before the main
floor screed is laid.
ffl
Figure 10.5 (d) Newel post skew-nailed into floor
Housed into Floor
Figure 10.5(c): The position of the newel post is
marked on the wooden or chipboard floor and
chopped out to form a shallow housing, equal to about
one-third of the floor thickness. The post should fit
this snugly and be skew-nailed into position.
Skew-nailed
Figure 10.5(d): Alternatively, on wooden or chipboard
floors, bottom newel posts are quite commonly cut off
at floor level, seated without any jointing and skewnailed into the floor material with 50 or 75 mm oval
nails, punched under the surface. The degree of rigidity achieved by this is minimal – and the newel post’s
stability depends mainly on the jointed connection to
the string and lower step(s); therefore, the gluing, pinning and screwing of these parts (see Figure 10.6)
should not be skimped.
Bolted to Joist or Nogging
Figure 10.5(e): Finally, on suspended wooden-joisted
floors, although more time-consuming, tedious and
rarely done in practice, the newel post achieves a far
greater degree of rigidity if it is taken through the
floor in its full sectional size and coach-bolted to a
joist or – more likely in practice – to a solid nogging.
According to the precise position of the newel post,
the nogging would be trimmed between nearby joists.
If not accessible below, pieces of flooring would have
to be left out to facilitate the insertion of the bolt.
Note that the type of staircase indicated in Figures
10.5(b)–(e) is nowadays quite common and has the
face of its first riser board central to the newel, without any protruding step. Although aesthetically less
attractive, it involves less expense.
112
Fixing Stairs and Balustrades
ffl
taper of about 25 mm length. After trying the newel
post into position, coat the joint with PVA (polyvinyl
acetate) glue and reposition the newel. This is best
done using a claw hammer onto a spare block of wood
held against the lower face of the newel. When a reasonable fit has been achieved, a touch of glue is placed
into the draw-bore holes and the tapered pins are
driven in until no part of the taper remains within the
newel – bearing in mind, however, that the lower
dowel usually clashes with the step on the other side.
Clean off excess glue with a damp rag or paper and
then cut off the surplus dowel ends with a fine saw,
near the newel’s surface. Clean off the remainder with
a block plane or smoothing plane.
10.2.10 Fitting a Protruding Step
Figure 10.5 (e) Newel post bolted to joist or nogging
3
10.2.9 Fixing the Newel
The bottom newel post, which will have been morticed and fitted during manufacture, is now ready to
be permanently fixed to the outer string. This can be
done with the staircase lying on its side or resting up
against the landing above and propped up on saw
stools, or similar, at the bottom. The mortice and
tenon joint should already be drilled to receive 12 mm
diameter wooden dowels (pins). The holes should be
slightly offset to enable the tapered pins to effect a
wedging action when driven in, so drawing up the
shoulders of the oblique (uncrampable by normal
means) tenons to a good fit against the post.
Procedure
Figure 10.6: If pins are not supplied, cut off pieces of
12 mm diameter dowel rod, about 50 mm longer than
the newel thickness and chisel the ends to a shallow
2
Fit into
string first
Position
of entr y
Then fit into newel
1
∗
∗Points to be eased
Figure 10.7 Fitting protruding bottom step
Figure 10.7: If the staircase has a bullnose (as illustrated)
or splay-ended bottom step, which protrudes beyond the
newel post, this is the next to be fixed. It should be realized that such steps cannot be attached during manufacture without the newel being permanently in position.
The step may have to be fitted and, as shown, this usually involves slight easings to the front end of the tread
entering the string housing, and the rear end of the tread
and face-edge of the bullnosed riser entering the newel
post housings. After a successful dry fit, glue the step
into position and drive in the glued string wedges, screw
the lower face of the second riser to the back-edge of the
tread and, finally, screw the ends of the bottom two risers
into the housings of the newel post.
10.2.11 Positioning the Staircase
Figure 10.6 Gluing and pinning bottom newel
∗
Figure 10.8(a): Set the staircase back into its ultimate
position, ready for the next operation of fitting and
fixing the handrail and top newel post. As with the
Installation Procedure
113
Upper floor
100 ⫻ 50
strut (kicker)
Figure 10.8 (a) Positioning staircase to facilitate
fixing of top newel and handrail
fixing of the bottom newel and step, the ideal position
for the staircase is on its side, but available space rarely
permits this, so methods of working in situ have to be
devised. One method, as illustrated, is to push the staircase forward until enough height has been gained above
the landing or upper floor to allow access to complete
the work from that level. To make this arrangement safe,
a temporary kicker strut or struts of 100 ⫻ 50 mm section, should be lodged against the nearest cross-wall and
should extend to support the base of the staircase.
However, this is usually discovered in the early stages
of offering up the staircase and may be proved to be
unnecessary.
10.2.13 Fixing the Top Newel and
Handrail
10.2.12 Notching the Top Newel
∗ Should equal riser thickness (plus at least 12 mm
tolerance, if necessary)
Strut
∗
Figure 10.8 (c) Fixing top newel and handrail
Figure 10.8 (b) Newel notched to fit trimmer
Figure 10.8(b): Next, the newel may need to be
notched-out (housed) to fit over the face of the landing
trimmer. If so, this has a certain advantage of providing
a good anchorage of the newel – and thereby that side
of the staircase – to the top landing. However, whether
this needs to be done or not depends on the newel’s
thickness, the thickness of the riser and whether a tolerance gap is to be allowed between the trimmer and
the riser board (Figure 10.8(b)). The main reason for a
tolerance gap is to overcome possible problems of the
landing being out of square with the staircase.
Figure 10.8(c): After checking the dry assembly of the
newel post and handrail in relation to both newels –
bearing in mind that all three would have been fitted
together previously by the manufacturer and drawbored – glue may be applied to the joints, the handrail
located in the lower-newel mortice and held suspended
while the top newel is fitted to the string and handrail
tenons. Moving speedily, as with all gluing operations,
the joints are knocked up and the glue-coated drawbore pins are driven in to complete the assembly of the
skeleton balustrade. Finally, remove the surplus dowels
and clean up as described previously.
10.2.14 Preparing Top Riser and
Nosing
Figure 10.9: Before the staircase can be set back into
position, the top riser and the landing-nosing have to
114
Fixing Stairs and Balustrades
Rear elevation
Pocket screws
Set the step-shaped riser/nosing into the glued housings of the newel and string, up against the glued
back-edge of the adjacent tread and insert the two
screws at each end, followed by the three or four
screws along the bottom edge. Clean off any excess
glue on the face side.
10.2.15 Final Positioning and Fixing
Figure 10.9 Preparing top riser and landing-nosing
be fitted and fixed to each other, to the string housings, the newel-post housings and to the adjacent
tread. This operation is often skimped, resulting in a
loose top riser and a squeaky top step. To avoid this,
attend to all the following points.
Detailed Procedure
Check that the rebated side of the nosing is equal to
the flooring thickness and, if thicker, ease with a rebate
or shoulder plane. Then measure between the housings
and cut the nosing and riser to the correct length. Now,
because this particular step cannot have glue blocks set
into its inner angle like the other steps (as they would
clash with the trimmer), the best way to strengthen the
joint is by pocket screwing. This is achieved by gouging
or drilling shallow niches into the upper back-face of
the riser board and by drilling oblique shank holes
through these to create at least three fixings to the
nosing piece. The riser is also drilled to receive two
screws at each end and three or four along the bottom
edge for the adjacent tread fixing.
Gluing Up
Next, glue the tongue-and-groove joint between the
riser and nosing piece and insert the pocket screws.
(a)
Figure 10.10: The staircase is now ready for fixing.
Remove the struts and lower carefully into position.
Re-check the newel posts for plumb and check that
the staircase is seated properly at top and bottom
levels. Fix the bottom newel to the floor; fix the top
newel to the trimmer by skew-nailing through the
side with two 75 mm or 100 mm oval nails or – better
still – by pocket-screwing (Figure 10.10(b)); nail the
nosing to the landing trimmer with 50 mm or 56 mm
floor brads or lost-head nails; then, finally, as
described earlier, fix the inner string to the wall.
10.2.16 String-to-skirting Abutment
Figure 10.11: Where wet plastering techniques are
being used (as they still are to some extent) and as
opposed to dry-lining methods, timber skirting
grounds should be fixed at least to the wall-string wall
beyond the two extremes of the wall string. This
ensures a flush abutment of the skirting where it
meets the string. In practice, it is wise to set the
grounds back 2 mm more than the given skirting
thickness from the face of the string. This combats the
effect of the timber ground swelling after gaining an
excess of moisture from the rendering/floating coat of
plaster. Note that the ground remains swollen, but the
subsequent setting coat of finishing plaster, which is
usually applied whilst the timber is swollen, remains
(b)
Figure 10.10 (a) Staircase finally in position (b) Skew-nailed or pocket-screwed to trimmer
Skew-nailed or
pocket-screwed
to trimmer
Installation Procedure
115
about 2 mm proud when the ground eventually loses
moisture and shrinks back to near normal.
90°
90°
10.2.17 String Mouldings
Figure 10.12: Finally, on the subject of wall strings, it
must be mentioned that they might be moulded on
their top edge to match the moulded edge – if any – of
the skirting member. This entails extra work in the
manufacture and/or on site, according to whether the
shaped edge is a stuck moulding (machined out of the
solid timber of the string and skirting), or a planted
moulding (a separate moulding fixed by nails or pins to
the plain, square edges of the string and skirting). As
illustrated, only the moulding is bisected at the angle
when planted, whereas with the stuck-moulded string
and skirting, it will be easier and acceptable to let the
bisected angle form a complete cut across the timber.
Figure 10.13 String-easings
moulding being stuck or planted, is either formed
during manufacture, or fixed on site. It must be said
that such work is uncommon nowadays because of the
cost and the disinterest generally in moulded work,
but could be met on repair, maintenance or refurbishment work.
10.2.19 Protection of Handrails,
Newels and Steps
Plaster
End of string
Ground
60 ⫻ 45
Handrail
Skirting thickness
ffl
Building paper
78 ⫻ 40
Handrail
Polythene bubblewrap
Figure 10.11 String-to-skirting abutment
70 ⫻ 70
Newel
Planted mouldings on string and skirting
Stuck mouldings
Figure 10.12 Mouldings
10.2.18 String-Easings
Figure 10.13: As well as being moulded and forming
obtuse and reflex angles, these string/skirting junctions might be required to be swept into a concave
shape at the bottom and a convex shape at the top.
This shaping is known as easing and, according to the
Figure 10.14 Protection of handrails, newels and steps
Figure 10.14: The remaining work on the staircase is
best left until the second fixing stage, after the plasterer or dry-liner and other trades are finished. In the
meantime, it is good practice to protect the handrail,
newels and steps just after a staircase is installed, by
wrapping building paper, heavy-gauge polythene or
polythene bubblewrap around the handrails and newel
posts and securing it with lashings of strong adhesive
tape. Newels, which are usually more vulnerable, can
be protected with additional wooden corner strips and
tied or taped. If the handrail – or the staircase – is of
hardwood, it should be sealed with diluted varnish
and allowed to dry before being covered. The treads
and risers should also be protected for as long as possible, by being covered with building paper or heavygauge polythene sheet, held into the shape of the steps
by lightly nailed tread boards.
116
Fixing Stairs and Balustrades
10.3 FIXING TAPERED STEPS
Traditionally, tapered steps – as they are now called –
were referred to as winders or winding steps and they
were incorporated into a variety of stair designs, used
to change the direction of flight either at the bottom,
halfway up, or at the top of the staircase. If the change
in direction was 180⬚, there would be six winding
steps, known as a half-space (half-turn) of winders. If
turning through 90⬚ – which was more common –
there would be three winding steps (the square
winder, the kite winder and the skew winder), known
as a quarter-space (quarter-turn) of winders.
This terminology equates to landings, identified as
quarter and half-space landings. Tapered steps usually
replace landings to improve the headroom and when
the ‘going’ of the staircase is greatly restricted. In certain cramped positions, there is often no alternative to
them being used at both the top and bottom of the
flight. However, tapered steps at middle and high
levels of a flight, although not against the current regulations, are generally considered to be potentially dangerous and are usually avoided.
handrails, but with newel posts) are now mainly used
at the bottom of the flight, in the form of four steps,
as illustrated, to effect a quarter-turn. Although it is
possible for some tapered-step arrangements to be
completely formed and assembled in the shop, it is
more common that they be formed and only partly
assembled, then delivered to the site for fitting and
fixing. The reasons for this, as with straight flights, are
for easier transportation and manoeuvrability through
doorways, etc., and for practical issues involved in the
fitting and fixing operation. Such a flight would arrive
on site separated from the newel posts and balustrade,
the top riser board, the landing nosings and apron linings, the return string, the tapered treads and their
corresponding riser boards, etc. The operations
involved in fitting and fixing this type of staircase are
generally the same as already described for straight
flights, with certain obvious additions, as follows.
10.3.2 Fitting the Main Flight
10.3.1 Tapered Steps at Bottom of
Flight
Figure 10.15: Tapered steps in non-geometrical staircases (those without wreathed strings and wreathed
Wall string
Dotted lines
indicate joint-lines
of built-up
boards
∗
First
parallel
step
Easing
String
Skew winder
Second half
kite-winder
∗
∗ Temporary
timber props
Easing
Figure 10.16 Fitting and checking the staircase
Half kitewinder
Square
winder
Return
string
Figure 10.15 Tapered steps at bottom of flight
Figure 10.16: First, the main flight is offered up and
fitted to the landing above and checked for level and
plumb. To achieve this, built-up packing will be
required at the bottom to compensate for the four
missing tapered steps. Alternatively, two short timber
props can be used, one under the bottom edge of the
extended wall string, the other, as illustrated, up
against the outer string, propping up the first available
Fixing Tapered Steps
tread board. If supported like this, the staircase should
remain firm, because, although not shown in the illustration, the end of the extended wall string butts up to
the return wall.
10.3.3 Fitting the Return String
The return string, which connects to the main wall
string with a tongued housing joint, is fitted and tied
into position, the tops of the long tread-housings then
being checked for level. The two strings ought to be at
right-angles to each other, but this will depend largely
on whether the return wall is truly square or not
(which is another good reason for assembling and
fitting these steps in situ).
10.3.4 Fixing the Main Flight
After these initial operations, the staircase will require
repositioning to allow for the fitting and fixing of the
newels and handrail. As outlined previously, this can
be done by pushing the staircase up onto the landing
and supporting the bottom end with packing and
struts. The fitting of the skeletal balustrade then follows the sequence:
1. fix bottom newel post by gluing and pinning to
string tenons;
2. glue handrail tenon and insert into bottom newel;
3. glue and fit top newel to handrail and outer string;
4. quickly complete the pinning of the unpinned
joints;
5. fix top riser and landing nosing – after joining same
together.
117
∗
3
4
Second
half-kite
∗
Skew
2
First
half-kite
1
Square
Pinch rod
Reference point
∗
Figure 10.17 (a) Pinch rod and tapered treads.
Tolerances in length are indicated by *
string) should be out of square. A common method
for checking lengths in this situation, is to use a pinch
rod formed by two overlapping laths (timber of small
sectional size). The laths are held together tightly,
expanded out to touch the two extremes, then marked
across the two laths with a pencil line as a reference
point, so that they can be released and put back
together when marking the tread and/or riser.
10.3.7 Checking, Cutting, Forming
and Fixing
2
3
4
Back into position again, the main flight is re-checked
and fixed as previously described. The tongued housing joint of the return wall-string is glued and fitted
and the string fixed to the return wall.
1
10.3.5 Starting on the Tapered
Steps
Finally, starting from the bottom, the tapered steps
have to be fitted and fixed. This is the most difficult
part of the whole operation and requires great care in
checking and transferring details of the tread’s shape
and length from the housings of the strings and
newel, to the separate treads.
10.3.6 Using a Pinch Rod
Figure 10.17(a): The treads will be already marked and
cut to a tapered shape, usually with tolerances of about
25 mm left on in length to offset any problems that
may arise if the return wall (and thereby the return
Figure 10.17 (b) Riser-end shapes into string and newel.
The dotted lines indicate nosings
Figure 10.17(b): Using such a method, the bottom riser
is checked and cut to length. Then, with the aid of a
carpenter’s bevel and the pinch rod, the first tapered
tread is checked, marked and cut to shape. After being
tied into position (which often involves easing protruding corners of the tread and/or housings), the tread
is fixed to the riser by gluing the joint between the two
boards and gluing, rubbing and pinning (with panel
pins) glue blocks on the inside angle. The housings are
then glued, the step inserted and glued-wedges driven
118
Fixing Stairs and Balustrades
This technique of checking and cutting, forming and
fixing, is repeated on the other tapered steps and finalized by the fixing of the last riser to the main flight
(riser No. 5). After each step is wedged into position,
the bottom of the riser should be screwed to the tread.
Sometimes, especially on wider-than-normal flights,
100 ⫻ 50 mm horizontal cross-bearers, on edge, are
notched into (or cleated to) the string and newel post
at each end, and fixed tight up against and under the
back edge of each tapered step.
good class work, because it finishes the balustrade off
properly against the wall adjacent to the bulkhead
trimmer and supports the return handrail on a
through mortice and tenon joint. On cheap work,
the handrail is housed in the wall, minus the half
newel. The half newel runs down past and up against
the side of the trimmer and is fixed to the finished
wall surface with three counter-bored screws. The
full-section newel sits in the corner of the stairwell,
again running down past the ceiling and up against
the trimmer on one side and the trimming joist
on the other. Although its rigidity will be gained from
the mortice-and-tenon connections of the handrails
that will joint into it at 90⬚ to each other, it should
still be counterbored and screwed to the trimmer
and trimming joists. The preformed handrail mortices
in the newels should be used as a datum point to
ensure that handrails will be level and/or parallel
to the floor.
10.4 FIXING BALUSTRADES
10.4.2 Level Handrails
into the string housings and screws driven into the
newel (as illustrated). On the bottom riser, at least, the
wedges cannot normally be driven-in on the string side
and will have to be tapered in thickness and driven-in
sideways from the face.
10.3.8 Repetition and Completion
During the second-fixing stage, the uncompleted
work on the staircase can be finished. This mainly
involves the balusters to the side of the staircase and
the balustrade around the edge of the stairwell on the
upper landing. The following steps outline the
sequence of the operation.
10.4.1 Additional Newel Posts
Mitred stub tenon
Through tenon
Handrails
Trimmed joist
Bulkhead trimmer
Half-newel
Corner newel
Trimming joist
Figure 10.18 (a) Plan view of additional newels
Figure 10.18(a): The number of newel posts needed to
form the balustrade to the stairwell depends on individual design, but normally only one and a half are
required in addition to the one already at the head of
the stairs. The half-section newel is always used on
Figure 10.18 (b) Plan view of level handrails
Figure 10.18(b): In the example used here, two
handrails – additional to the first raking handrail
used – will be required, one long, one short. If supplied from a joinery works, they may be already
tenoned at one end, but not usually at both, as tolerance must be allowed for site variations. Tenons –
their size taken from the newel mortices – should be
cut and shouldered carefully with a fine saw. The
handrail can be laid against the newels, with the
shoulder butted against one, while the second shoulder is marked against the other newel. This mark can
be squared around the shaped handrail by wrapping a
piece of straight-edged cardboard or glasspaper tightly
round the handrail until its edge overlaps precisely,
then by sliding along to the mark and marking around
the edge. Now mark and rip the tenon’s length, then
shoulder it. Where the tenons intersect in the corner
newel, they will require mitring.
Fixing Balustrades
119
10.4.3 Take Care on the Return
10.4.5 Nosing Pieces
Take care when marking the short return-handrail
length that the measurement between newels may differ between the top and at floor level, depending on
the plumbness of the half newel against the wall surface. All of the tenons should be draw-bored, glued
and pinned with 9 mm diameter dowelling. The
handrails can now be installed and, to facilitate this,
the fixings of the newels will require to be slackened
or – more likely – removed.
Having cut the apron linings carefully in length to fit
neatly and tight between newels, they are fixed at top
and bottom edges with 56 mm oval or lost-head nails
(punched under the surface) at maximum 600 mm
centres. Next, the nosing pieces, which are to be
attached to the top edge of the apron lining and the
joist, being like stair nosings, are usually equal in
thickness to the stair treads. Therefore, they will probably be rebated to meet the lesser thickness of the
flooring and this should be checked accordingly before
fixing. This done, cut carefully to length and nail into
position to the joist and apron-lining edges. If the
apron lining is of MDF board, it will be better to glue
this connection, not nail it, as MDF does not take or
hold nails very well in its edges.
10.4.4 Apron Linings and Nosing
Newel post
Baluster
Landing capping
Nosing
Apron
lining
10.4.6 String-capping and Landingcapping
Infill strips (spacers)
Trimmer/
trimming
joist
String
Figure 10.18 (c) Vertical section through apron lining
and nosing
Figure 10.18(c): Next in sequence are the apron linings
which add a finish to the rough face of the
trimmer/trimming joists within the open stairwell.
Traditionally, they were made from solid timber of
about 21 mm thickness, but nowadays they are more
common in plywood or MDF board. Their lateral
position in relation to the newel’s thickness is critical,
because they support the landing nosing above, which
in turn supports the balusters that must be dead centre
of the newel in order to relate to the underside groove
of the handrail. Therefore, they need to be very near
the centre of the newel, as seen in the illustration,
which usually means packing them out from the joists.
This is done with prepared or sawn timber grounds of
whatever thickness, but say 18 mm (⫻ 50 mm), fixed
horizontally on the joists to take MDF or plywood,
but vertically as so-called soldier-pieces at 400–600 mm
centres if the apron lining is of solid timber. This is to
combat the undesirable effect of cupping which may
occur to tangentially sawn boards.
Figure 10.18 (d) Sections through string and landing
capping
Figure 10.18(d): Capping is the next item to be fixed
and it can be either plain-edged or moulded and
grooved on one or both faces. One groove fits the top
edge of the string, the other houses the balusters. If
there is only one groove, then this houses the balusters
and the plain (ungrooved) face is fixed to the string.
Similarly, it can also be used on the landing, as illustrated in Figure 10.18(c), fixed to the nosing with
50 mm oval nails. This has the advantage of providing
a raised edge for carpet to butt up against. On the
string, the capping needs to be cut to an angle to fit
against the newels. This can be found with a sliding
bevel, set to the angle formed by the junction of the
bottom (or top) newel and the string. Set the chop
saw (or a mitre box) up with this bevel, cut carefully to
length and fix with 38 mm oval nails at about 500 mm
centres.
120
Fixing Stairs and Balustrades
10.4.7 Balusters
A
B
a
c
d
d
b
d
c
_
2
Figure 10.18 (e) Baluster stick A and spindle B
Figure 10.18(e): Balusters are also referred to nowadays
as spindles. Both names refer to lathe-turned ornamental
posts that infill the balustrade at the side of the stairs
and stairwell. Baluster sticks only differ by being square
posts with no ornamental lathe work. Whichever is
used, The Building Regulations require that they be set
up with a controlled gap between them. This gap should
not allow a 100 mm diameter sphere to pass through. In
effect, this means that the spacing between the balusters
should not be more than 99 mm. The same bevel set up
to cut the capping can now be used to cut the balusters
to fit the raking balustrade. First, cut one only, bevelled
at each end to the precise height taken from the inner
face of the newel. Try it in position in a few places and
check for plumb. If acceptable, cut the estimated number to this pattern, ready for fixing.
10.4.8 Support from Above
If possible, support the centre of the handrail from
above with a timber strut at right-angles to the pitch,
to restrict the cumulative effect of the individually
fixed balusters pushing up the handrail. Alternatively,
fix a single baluster midway between newels and use a
sash cramp at this point, square across the balustrade,
tightened from the top of the handrail to the underside of the string.
10.4.9 Infill Strips
Figure 10.18(f ): The correct spacing – and easy fixing –
of the balusters is achieved by using short lengths of
timber infill-strip between them at top and bottom.
This thin strip, machined to fit the shallow groove (of
say 6 ⫻ 40 mm) in the handrail and the capping (as in
Figure 10.18 (f) Working out spindle spacings
Figure 10.18(d)) is cut up into equal angled-lengths,
worked out to achieve the required spacing gap. One
way of doing this, is to set up a pre-cut baluster in the
grooves of the capping and handrail near, say, the bottom newel post and slide/adjust its position until a
reading of 99 mm is obtained on a right-angled measurement a. The geometrically longer measurement of
the angled infill strip will now be obtainable as b,
between the newel and baluster faces.
10.4.10 Creating Equal Gaps
Throughout
Figure 10.18( f ): To test the overall spacing of the
balusters, the raking measurement b just obtained
should have the raking thickness of the baluster c added
to it, giving d. This value – equalling the baluster
centres – should then be divided into the total measurement of the capping between the newels plus the
raking thickness of half a baluster at each end, i.e.
c 2 ⫻ 2 ⫽ c ⫹ capping length. The odds are that it
will not divide equally and therefore adjustments will
need to be made by lessening the divisor d and dividing again – and again, if necessary – until it works out
without a remainder. The difference between the first
and final divisor must then be deducted from the firstobtained measurement of the angled infill-strip b.
10.4.11 Example
Assume that the total length of capping between
newels ⫽ 3.188 m, actual baluster thickness ⫽ 40 mm,
Fixing Balustrades
desired gap a ⫽ 99 mm, initially obtained rakingmeasurement of infill strip b ⫽ 129 mm, raking thickness of baluster c ⫽ 52 mm. Therefore,
121
10.4.13 Newel Caps
Figure 10.18(g): The tops of newels are usually
finished in three basic ways:
b ⫹ c ⫽ 129 ⫹ 52 ⫽ 181 mm baluster centres d
The divisible length of capping between newels plus
two times the half-baluster raking-thickness is
3.188 m ⫹ 2 ⫻ 26 mm ⫽ 3.240 m
Therefore
3240 181 17.90
1
2
3
4
6
7
8
9
5
17 spacings with 90 mm remainder
Trying again,
3240 180 18 spacings exactly
The difference between divisors equals 1 mm, therefore the final size for the angled infill-strips b is
129 1 128 mm
In this example, the resultant gap between balusters
will be slightly more than 98 mm. The working out
also tells us that, as there are 18 spacings, there must
be 17 balusters and 36 angled infill-strips.
10.4.12 Fixing
The infill strips should now be cut and the first two,
one in the handrail, one in the capping groove, fixed
up against the bottom newel post with a few 18 or
25 mm panel pins punched-in. Then the first baluster
is fixed, skew-nailed at top and bottom with two
38 mm lost-head oval nails (punched-in) at each end.
Then two more angled infill-strips are fixed, and
another baluster – and so the process is repeated until
the top newel is reached. On the landing, a similar
technique of working out and fixing can be used for
the stairwell balusters. The only variation is when a
grooved capping is not used. In these situations, as
was traditional, the balusters are housed into the
nosing to a depth of about 6 mm (Figure 10.18(e))
and skew-nailed once from each side.
Figure 10.18 (g) Newel caps
1. finished in themselves, shaped in a variety of simple
designs such as (1) chamferred-edge, (2) round(quadrant) edge, (3) cross-segmental top and
(4) cross semi-circular top.
2. separate recessed, square caps, with projecting
moulded edges (5). The caps are pinned or nailed
to the tops of the newels.
3. separate spherical ornate caps turned on the lathe
with projecting spigots, ready to be glued and
inserted into predrilled holes in the ends of the
newel posts. Three standard shapes predominate in
this range, known as (6) mushroom cap, (7) ball cap
and (8) acorn cap.
Usually, on newel posts above ground floor level, the
newel is allowed to project down below the ceiling (by
minimal amounts nowadays) and should receive an
identical cap (9) to that used at the top. Traditionally,
these below-ceiling projections were known as
newel-drops or pendants.
11
Stair Regulations Guide to
Design and Construction
11.1 THE BUILDING
REGULATIONS 2000
Handrail
both sides
The going is measured
between alternate nosings
11.1.1 Approved Document K, 1998
Edition, Amended 2000
This approved document, amended in 2000, came
into effect on 1 January. Three categories of stairs are
considered in the document:
1. private stair, intended to be used for only one
dwelling;
2. institutional and assembly stair, serving a place
where a substantial number of people will gather;
3. other stair, in all other buildings.
In producing a modified version of the approved document’s K1 section here (hereinafter referred to as AD
K1), covering most of the points concerning stairs and
balustrades only, an attempt has been made to present
a clearer picture of stair regulations as a guide, but not
as a substitute.
11.1.2 Definitions
The following meanings are given to terms used in the
document and a few other definitions have been
added for clarity.
Alternating tread stair
Figure 11.1: A stair constructed of paddle-shaped
treads with the wide portion alternating from one side
to the other on consecutive treads.
Going not less than
220 mm
Rise not more than
220 mm
Figure 11.1 Alternating tread stair
Deemed Length
Figure 11.3: If consecutive tapered treads are of different
lengths, as illustrated, each tread can be deemed to have a
length equal to the shortest length of such treads.
Although not now referred to in AD K1, the deemed
length (DL) needs to be established on certain stairs (see
Figure 11.20(a)) for the purpose of defining the extremities to which the pitch line(s) will apply.
Flight
The part of a stair or ramp between landings that has
a continuous series of steps or a continuous slope.
Balustrade
Going
Figure 11.2: A protective barrier comprising newel
posts, handrail and balusters (spindles), which may
also be a wall, parapet, screen or railing.
Figure 11.4: The horizontal dimension from the
nosing edge of one tread to the nosing edge of the
next consecutive tread above it, as illustrated.
The Building Regulations 2000
123
Going of a Landing
∗ Non-entry
area for notional
sphere of 100 mm
diameter
(c)
Going of
landing
(b)
∗
∗
∗
∗
∗ ∗ ∗
(a)
Figure 11.5 Landings = (a)(b)(c)
NLT stairway
Figure 11.2 Balustrade
∗
∗
Figure 11.6 Going of landings not less than stairway
DL
∗
DL
Figures 11.5 and 11.6: The horizontal dimension
determining the width of a landing, measured at
right-angles to the top or bottom step, from the nosing’s edge to the wall surface or balustrade.
∗
+ = Centre point for DL
and tapered treads ∗
DL
Helical Stair
A stair that describes a helix round a central void,
traditionally known as a geometrical stair.
Nosing
Figure 11.3 Deemed length (DL)
Figure 11.7: The projecting front edge of a tread board
past the face of the riser, not to be more than the
Nosings
Pitch line
Tread
Going
Width of
tread
Rise
Pitch
Figure 11.4 Going, rise and pitch
Figure 11.7 Nosings
124
Stair Regulations Guide to Design and Construction
tread’s thickness, as an established joinery rule, and
not less than 16 mm overlap with the back edge of the
tread below on open-riser steps, as shown in diagram 1
in AD K1.
Tapered Tread
Pitch
11.1.3 General Requirements for
Stairs
Figure 11.4: This refers to the degree of incline from
the horizontal to the inclined pitch angle of the stair.
Figure 11.3: A step in which the nosing is not parallel
to the nosing of the step or landing above it.
Steepness of Stairs
Pitch Line
Central
pitch line
In a flight, the steps should all have the same rise and
the same going to the dimensions given later for each
category of stair in relation to the 2R ⫹ G formula.
Alternative Approach
AD K1 states that the requirement for steepness of
stairs can also be met by following the relevant recommendations in BS 5395: Stairs, ladders and walkways
Part 1: 1977 Code of practice for the design of straight
stairs.
NMT 42°
pitch
2R + G
R
Construction of Steps
G
NLT 220 mm
going
R
Minimum goings
NLT 50 mm
NLT 16 mm
overlap on
open-riser steps
Non-entry area for notional
sphere of 100 mm diameter
Figure 11.8 Pitch line
Figure 11.9 Step construction
Figures 11.4 and 11.8: This is a notional line used for
reference to the various rules, which connects the nosings of all the treads in a flight and also serves as a line
of reference for measuring 2R ⫹ G on tapered-tread
steps.
Figure 11.9: Steps should have level treads and may
have open risers, but treads should then overlap each
other by at least 16 mm. For steps in buildings providing the means of access for disabled people, reference
should be made to Approved Document M: Access and
facilities for disabled people.
Rise
Open-riser Stair
Figure 11.4: The vertical dimension of one unit of the
total vertical division of a flight (total rise), as illustrated.
Spiral Stair
A stair that describes a helix round a central column.
Stair
A succession of steps and landings that makes it possible to pass on foot to other levels.
Figure 11.9: All stairs that have open risers and are
likely to be used by children under 5 years should be
constructed so that a 100 mm diameter sphere cannot
pass through the open risers.
Headroom
Figures 11.10 and 11.11: Clear headroom of not less
than 2 m, measured vertically from the pitch line or
landing, is adequate on the access between levels, as
illustrated. For loft conversions where there is not
The Building Regulations 2000
125
Width
of flight
Headroom
NLT 2 m
Headroom
NLT 2 m
Joinery width of staircase
Figure 11.12 Width
Figure 11.10 Headroom
Dividing Flights
Figure 11.13: A stair in a public building which is
wider than 1800 mm should be divided into flights
which are not wider than 1800 mm, as illustrated.
NMT 1.8 m
NMT 1.8 m
1.9 m
1.8 m
Width (w)
Figure 11.13 Division of flights if over 1.8 m wide
w
_
2
Length of Flights
Not less than
stair width
Figure 11.11 Reduced headroom for loft conversions
Flight
Flight
enough space to achieve this height, the headroom
will be satisfactory if the height measured at the
centre of the stair width is 1.9 m, reducing to 1.8 m at
the side of the stair.
Width of Flights
Figure 11.12: Contrary to previous regulations (which
gave 800 mm as the minimum unobstructed width for
the main stair in a private dwelling), no recommendations for minimum stair widths are now given. However, designers should bear in mind the requirements
for stairs which:
●
●
form part of means of escape (reference should be
made to Approved Document B: Fire safety);
provide access for disabled people (reference should
be made to Approved Document M: Access and facilities for disabled people).
Stair
width
Landing
Not less
than 30°
Figure 11.14 Change of direction
Figures 11.14 and 11.16: The number of risers in a
flight should be limited to 16 if a stair serves an area
used as a shop or for assembly purposes. Stairs having
more than 36 risers in consecutive flights, should have
at least one change of direction between flights of at
least 30⬚ in plan, as illustrated.
Landings
Figures 11.5, 11.6 and 11.15: A landing should be provided at the top and bottom of every flight. The width
126
Stair Regulations Guide to Design and Construction
Stair
width
Stair
width
NLT
220 mm
Flight
Up
Up
NLT
400 mm
NLT
400 mm
Landing
NMT
220 mm
NMT 16
rises
per
flight
NMT 42°
pitch
Door
Door
(a)
Figure 11.16 Category 1 stair
Cupboard
NLT
400 mm
Note that for means of access for disabled people, reference should be made to Approved Document M:
Access and facilities for disabled people.
Institutional and Assembly Stair (Category 2)
Up
NLT
280 mm
(b)
Figure 11.15 (a) Landings next to doors (b) Cupboard
on landing
and length of every landing should be at least as long
as the smallest width of the flight and may include
part of the floor of the building. To afford safe passage, landings should be clear of permanent obstruction. A door may swing across a landing at the bottom
of a flight, but only if it will leave a clear space of at
least 400 mm across the full width of the flight. Doors
to cupboards and ducts may open in a similar way over
a landing at the top of a flight (Figure 11.15(b)). For
means-of-escape requirements, reference should be
made to Approved Document B: Fire safety. Landings
should be level unless they are formed by the ground
at the top or bottom of a flight. The maximum slope
of this type of landing may be 1 in 20, provided that
the ground is paved or otherwise made firm.
11.1.4 Rise-and-going Limits for Each
Category of Stair
NMT
180 mm
NMT 16
rises
per
flight
No pitch
regulation
Figure 11.17 Category 2 stair
Figure 11.17: Any rise between 135 mm and 180 mm
can be used with any going between 280 mm and
340 mm. Note that for means of access for disabled
people, reference should be made to Approved
Document M: Access and facilities for disabled people.
Other Stair (Category 3)
Figure 11.18: Any rise between 150 mm and 190 mm
can be used with any going between 250 mm and
320 mm. Note that reference to Approved Document M:
Access and facilities for disabled people also applies here.
Private Stair (Category 1)
Pitch
Figure 11.16: Any rise between 155 mm and 220 mm
can be used with any going between 245 mm and
260 mm, or any rise between 165 mm and 200 mm can
be used with any going between 220 mm and 300 mm.
Figure 11.15: The maximum pitch for a private stair is
42⬚. Note that recommended pitch angles for the
other two categories of stair are not given. However,
using the criteria that are given, if the maximum rise
The Building Regulations 2000
NLT
250 mm
127
Rise
Going
NMT
190 mm
NMT 16
rises
per
flight
Rise
2R + G = NLT 550/NMT 700 mm
No pitch
regulation
Figure 11.19 Design formula
Figure 11.18 Category 3 stair
and the minimum going were used in these categories,
the maximum possible pitch for category 2 would be
33⬚ and for category 3 would be 38⬚.
Note that if the area of a floor of a building in category 2 (Institutional and assembly stair) is less than
100 m2, the going of 280 mm may be reduced to
250 mm. Therefore, with maximum rise and minimum
going, the maximum possible pitch would be
increased from 33⬚ to 36⬚.
The 2R⫹G Design Formula
Figure 11.19: In all three categories, the sum of
the going plus twice the rise of a step (traditionally
220
210
Viability Graph
Figure 11.20: This graph can be used to test the viability and legality of various permutations in rise and
going for the Category 1, Private Stair Regulations.
Any step-sizes that fall into Area A, meet the permitted rise and going, but violate the maximum pitch
regulation. Area C meets the various regulations, but
violates the traditionally established minimum pitch
of 25⬚. Area D violates the maximum of 2R⫹G
(700 mm), and Area E violates the minimum of
Going (in mm)
NLT
NMT 220
established as 2R ⫹ G) should be not less than 550 mm
nor more than 700 mm (subject to the criteria laid down
for tapered treads).
240
260
280
300
320
340
360
A
Area D
200
190
180
Area B
Rise (in mm)
170
160
150
Area C
140
130
120
110
Area E
100
90
NLT
80
75
Figure 11.20 Category 1 Private
Stair’s graph
128
Stair Regulations Guide to Design and Construction
2R⫹G (550 mm). However, the ratio of any rise and
going within Area B, meets the various regulations.
where the curved pitch line touches the nosings
(Figure 11.8).
2. If the width of the stair is 1 m or more, it should be
measured at 270 mm from each side, tangentially
where each curved pitch line touches the nosings
(Figure 11.21(c)). The minimum going of tapered
treads should not be less than 50 mm, measured at
right angles to a nosing in relation to the nosing
above. Where consecutive tapered treads are used, a
uniform going should be maintained. Where a stair
consists of straight and tapered treads, the going of
11.1.5 Special Stairs
Tapered Treads
Figures 11.8 and 11.21: For a stair with tapered treads,
the going and 2R⫹G should be measured as follows.
1. If the width of the stair is less than 1 m, it
should be measured in the middle, tangentially
6
5
4
270
Wall string
4
Pitch
line
Long pitch line
3
CL
2
Short pitch line
2
Newel
post
1
1
270
D
L
_
2
Stairway
Compulsory
inner handrail
270
3
Wall string
270
Stairway
Deemed width
line
Outer string
Centre line of
outer handrail
Radial point
Two pitch lines if stairway
is 1 m or more in width
Single pitch line if stairway
less than 1 m
(a)
(b)
Imaginary, vertical
planes formed
by pitch lines,
for checking
the various rules
Pitch
R
G
2R + G
R
R
G
R
270
Going
270
(c)
Figure 11.21 (a) Single pitch line; (b) two pitch lines if stairway is 1 m or more in width; (c) imaginary vertical planes
The Building Regulations 2000
the tapered treads should not be less than the
going of the straight flight.
Note that BS 585: Wood stairs Part 1: 1989
Specification for stairs with closed risers for domestic use,
including straight and winder flights and quarter or half
landings is given in AD K1 as a British Standard
which will offer reasonable safety in the design of
stairs.
One handrail
Two handrails
at least if
stairway is less
than 1 m
if stairway is wider
than 1 m
129
Spiral and Helical Stairs
It is further recommended in AD K1 that stairs
designed in accordance with BS 5395: Stairs, ladders
and walkways Part 2: 1984 Code of Practice for the
design of helical and spiral stairs, will be adequate.
Stairs with goings less than shown in this standard
may be considered in conversion work when space is
limited and the stair does not serve more than one
habitable room.
(a)
Alternating Tread Stairs
Figure 11.1: This type of stair is designed to save space
and has alternate handed steps with part of the tread
cut away; the user relies on familiarity from regular
use for reasonable safety. Alternating tread stairs
should only be installed in one or more straight flights
for a loft conversion and then only when there is not
enough space to accommodate a stair which satisfies
the criteria already covered for Private stairs. An alternating tread stair should only be used for access to one
habitable room, together with, if desired, a bathroom
and/or a WC. This WC must not be the only one in
the dwelling. Steps should be uniform with parallel
nosings. The stair should have handrails on both sides
and the treads should have slip-resistant surfaces. The
tread sizes over the wider part of the step should have
a maximum rise of 220 mm and a minimum going of
220 mm and should be constructed so that a 100 mm
diameter sphere cannot pass through the open risers.
Fixed Ladders
A fixed ladder should have fixed handrails on both
sides and should only be installed for access in a loft
conversion – and then only when there is not enough
space without alteration to the existing space to
accommodate a stair which satisfies the criteria
already covered for Private stairs. It should be used for
access to only one habitable room. Retractable ladders
are not acceptable for means of escape. For reference
to this, see Approved Document B: Fire safety.
Handrails for Stairs
Figure 11.22: Stairs should have a handrail on at least
one side if they are less than 1 m wide and should have
∗
∗
(b)
Figure 11.22 (a) Handrails for stairs; (b) Bottom steps *
a handrail on both sides if they are wider. Handrails
should be provided beside the two bottom steps in
public buildings and where stairs are intended to be
used by people with disabilities. In other places,
handrails need not be provided beside the two bottom
steps (Figure 11.22(b)).
Handrail Heights
Figure 11.23: In all buildings, handrail heights should
be between 900 mm and 1000 mm, measured vertically to the top of the handrail from the pitch line or
floor. Handrails can form the top of a guarding, if the
heights can be matched.
Guarding of Stairs
Figure 11.2: As illustrated, flights and landings should
be guarded at the sides:
●
●
in dwellings when there is a drop of more than
600 mm;
in other buildings when there are two or more
risers.
Figure 11.23 Handrail heights
NLT 900 mm NMT 1 m
Stair Regulations Guide to Design and Construction
NLT 900 mm NMT 1 m
130
The guarding to a flight should prevent children
being held fast by the guarding, except on stairs in a
building which is not likely to be used by children
under 5 years. In the first case, the construction should
be such that
●
●
a 100 mm diameter sphere cannot pass through any
openings in the guarding;
children will not readily be able to climb the guarding (this in effect means that horizontal ranch-style
balustrades used in recent years should not now
be used).
The height of the guarding is given in Figure 11.23
for single-family dwellings in category 1. External
balconies should have a guarding of 1100 mm.
12
Constructing Traditional
and Modern Roofs
12.1 INTRODUCTION
Roofing in its entirety is an enormous subject, but the
practical issues that involve the first-fixing carpenter
on the most common types of dwelling-house roof –
dealt with here – are less formidable.
with sheet-boarding and (for economy) bituminous felt
in built-up layers. Pitched and lean-to roofs are covered
with quarried slates (which are very expensive) or nonasbestos-cement slates, blue/black in colour, a cheaper
lookalike, clay tiles (also expensive) or, more commonly,
concrete tiles on battens and roofing (sarking) felt.
12.1.2 Knowledge Required
12.1.1 Types of Roof
Pitched roof (more than 10°)
Flat roof (10° or less)
Roofing carpenters nowadays, ideally, require a knowledge of both modern and traditional roof construction –
and a sound knowledge of at least one of the various
methods used for finding lengths and bevels of roofing
members. The various methods dealt with later include
geometry (to develop an understanding of finding bevels
and lengths, but not meant to be used in practice), steel
roofing square or metric rafter square, the Roofing
Ready Reckoner and last, but not least, the Roofmaster,
a revolutionary device invented by Kevin Hodger, formerly a carpentry lecturer at Hastings College.
12.1.3 Traditional Roofing
Lean-to roof
(more than 10°)
This consists basically of rafters pitched up from wall
plates to a ridge board, such rafters being supported
by purlins and struts which transfer the load to either
straining pieces or binders and ceiling joists to an
internal load-bearing wall.
12.1.4 Modern Roofing
Figure 12.1 Types of roof
Figure 12.1: The three types of roof to contend with are
flat, lean-to and pitched. Timber is used for the skeleton
structure to form a carcase and this is covered with various impervious materials. Flat roofs are usually covered
Modern roofing, using trussed-rafter assemblies, often
uses smaller sectional-sized timbers and normally only
requires to be supported at the ends. This frees the
designer from the need to provide intermediate loadbearing walls and dispenses with purlins and ridge
boards. Other differences are that traditional roofing
is usually an entire site operation, whereas trussedrafter roofing involves prefabrication under factory
conditions and delivery of assembled units to the site
for a much-reduced site-fixing operation.
132
Constructing Traditional and Modern Roofs
12.2 BASIC ROOF DESIGNS
12.2.1 Introduction
Gable roof
12.2.3 Hipped (or Hip-ended) Roof
This design is also used in modern roofing, but to a
lesser extent. The hipped ends are normally the same
pitch as the main roof and therefore each hip is 45⬚ in
plan. In traditional roofing, the purlins are continuous
around the roof and all the old roofing skills are needed.
In modern roofing, the hip-ends are either constructed
traditionally (by cut and pitch methods) or by using hip
trusses supplied with the main trusses; either way, a
method for finding lengths and bevels will be required
at this stage.
12.2.4 Hip and Valley Roof
As illustrated in Figure 12.2, valleys occur when roofs
change direction to cover offshoot buildings.
Hipped roof
Hip and valley roof
12.2.5 Gambrel Roof and
Jerkin-head Roof
Gablet
Gambrel or
hipped-gablet roof
Gable-ended
mansard roof
Jerkin-head or
hipped-gable roof
Hip-ended
mansard roof
Figure 12.2 Basic roof designs
Figure 12.2: Traditional pitched roofs, by virtue of
having been in existence for centuries, predominantly
outnumber modern roofs and therefore can be easily
spotted for reference and comparison. Their design
was often used to advantage in complementing and
enhancing the beauty of a dwelling and variations on
basic designs can be seen to be infinitely variable. Still
occasionally required on individual, one-off dwellings
being built, the main features of traditional roofs are
described below.
12.2.2 Gable Roof
This design is now widely used in modern roofing
because of its simplicity and therefore relatively lower
cost. As illustrated, triangular ends of the roof are
formed by the outer walls, known as gable ends.
Traditionally, purlins took their end-bearings from
these walls.
As illustrated, these roofs include small design innovations to the basic hipped and gable roofs. Gambrel
roofs can be built traditionally as normal hipped roofs
with the full-length hips running through, under the
gablets, and the ridge board protruding each end to
accommodate the short cripple rafters – and jerkinhead roofs simply have shorter hips. Both types can be
built with modern trussed-rafter assemblies.
12.2.6 Mansard Roofs
Apart from their individual appearance being a reason
for using such a roof, the lower, steeper roof-slopes,
which were vertically studded on the inside, acted as
walls and accommodated habitable rooms in the roof
space. The upper, shallower roof slopes had horizontal
ceiling joists acting as ties, giving triangular support to
the otherwise weak structure. Technically, these roofs
usually incorporated king-post trusses superimposed
on queen-post trusses. This design of roof has been
built using modern techniques, especially involving
steel beams, taking their bearings from gable ends.
12.3 ROOF COMPONENTS
AND TERMINOLOGY
12.3.1 Wall Plates
Figure 12.3(a): 100 ⫻ 75 mm or 100 ⫻ 50 mm sawn
timber bearing plates, are laid flat and bedded on mortar to a level position, flush to the inside of the inner
wall and running along the wall to carry the feet of all
Roof Components and Terminology
133
Ceiling
joist
Common rafter
Wall plate
Restraint strap
(a)
(b)
Sealed cavity-wall
18 mm plywood
saddle
board
25 mm Gauged
pencil line
Ridge
board
Second
common
rafter
First
common
rafter
Saddle
board
Crown
rafter
Hip
Ridge
Crown
(c)
Rafter-offcut
fixed to underside
of crown rafter
to increase plumb
bearing for hips
First common
rafters
(d)
the rafters and the ends of the ceiling joists. Nowadays,
the wall plates must be anchored down with restraint
straps.
12.3.2 Restraint Straps
Figure 12.3(b): Vertical, galvanized steel straps, 2.5 mm
thick, 30 mm wide, with 6 mm holes at 15 mm offset
centres and lengths up to 1.5 m, are fixed over the wall
plates and down the inside face of the inner skin of
blockwork at maximum 2 m intervals. Additional straps
should be used to reinforce any half-lap wall plate joint.
Horizontal straps of 5 mm thickness are used across the
ceiling joists and rafters, to anchor the gable-end walls.
Plan
view
Figure 12.3 (a)–(d) Principal
roof components
They should bridge across at least three of these structural timbers and have noggings and end packing fixed
between the bridged spaces. These noggings should be
at least 38 mm on the face-side by half the depth of
joist or rafter.
12.3.3 Ceiling Joists
Figure 12.3(a): Like floor joists, these should span the
shortest distance, rest on and be fixed to the wall plates,
as well as to the foot of the rafter on each side – thereby
acting as an important tie and also providing a skeleton
structure for the underside-boarding of the ceiling.
Usually, 100 ⫻ 50 mm sawn timbers are used.
134
Constructing Traditional and Modern Roofs
12.3.4 Common Rafters
Figures 12.3(a) and (c): Again, 100 ⫻ 50 mm sawn
timber is normally used for these load-bearing ribs
that pitch up from the wall plate on each side of the
roof span, to rest opposite each other and be fixed to
the wall plate at the bottom and against the ridge
board at the top.
Hip
rafters
Ridge
board
12.3.5 Ridge Board
Common
rafters
Saddle
board
Figure 12.3(c): This is the spine of the structure at the
apex, running horizontally on edge in the form of a
sawn board of about 175 ⫻ 32 mm section (deeper on
steep roofs, depending upon the depth of the commonrafter splay cut ⫹ 25 mm allowance) against which the
rafters are fixed.
Crown
rafter
12.3.6 Saddle Board
Figures 12.3(c) and (d): The saddle board is a purposemade triangular board (usually of 18 mm WBP exterior
plywood), like a gusset plate, fixed at the end of the ridge
board and to the face of the first pair of common rafters.
It supports the hips and crown rafter of a hipped end.
12.3.7 Crown or Pin Rafter
Figures 12.3(c) and (d): This is the central rafter of a
hipped end.
Saddle
board
Hips
Crown
Ridge board
First
common
rafter
Second
common
rafter
Figure 12.4 (a) Alternative hip-arrangement
12.3.8 Alternative Hip-arrangement
This is shown in plan and isometric views in Figure 12.4.
saddle board at the end of the ridge. They act as a spine
for the location and fixing of the jack rafter heads.
12.3.9 Terminology
Figure 12.4(b): This isometric view of a single-line
roof carcase shows the majority of components in
relation to each other and defines such terminology as
eaves, verge, gable end, etc.
12.3.10 Angle Tie
Figure 12.5(a): Sometimes a piece of 75 ⫻ 50 mm or
50 ⫻ 50 mm timber, acting as a corner tie across the
wall plates, replaces the traditional and elaborate
dragon-tie beam used to counteract the thrust of the
hip rafter. Alternatively, a simplified, modern, metal
dragon-tie (Figure 12.5(b)) may be used. Either one of
these restraints to the hip is recommended, especially
on larger-than-normal roofs.
12.3.11 Hip Rafters
Figure 12.5(a): Similar to ridge boards, hip rafters pitch
up from the wall-plate corners of a hipped end to the
12.3.12 Jack Rafters
Figure 12.5(a): These are rafters with a double (compound) splay-cut at the head, fixed in diminishing
pairs on each side of the hip rafters.
12.3.13 Valley Rafters
Figure 12.5(c): Valley rafters are like hip rafters, but
form an internal angle in the roof-formation and act
as a spine for the location and fixing of the cripple
rafters. Sectional sizes are similar to ridge board and
hip rafters.
12.3.14 Cripple Rafters
Figure 12.5(c): These are pairs of rafters, diminishing
like jack rafters, spanning from ridge boards to valley
rafter and gaining their name traditionally by being
cut off at the foot.
Roof Components and Terminology
135
Ridge board
Common rafter
Gable
end
Purlin
Valley rafter
Cripple rafter
Eaves
Verge
Eaves
Crown
rafter
Jack rafter
Purlin
Hip rafter
Eaves
Wall plate
Gable
end
Hipped
end
Corner
wallplates
Hip
rafter
Angle tie
(a)
Ridge board
Jack
rafter
Figure 12.4 (b) Isometric
view of single-line roof
carcase
Metal
Dragon-tie
(b)
Ridge board
Common rafters
Hanger
Binder
Ceiling joist
Valley
rafter
Figure 12.5 (a)–(d) Other roof components
Hanger
Struts
Straining
piece
Common
rafter
Cripple rafters
(c)
Purlins
Collar
(d)
Binder
Load-bearing
partition wall
136
Constructing Traditional and Modern Roofs
12.3.15 Purlins
Figure 12.5(d): Purlins are horizontal beams, about
100–150 ⫻ 75 mm sawn, that support the rafters midway between the ridge and the wall plate, when the
rafters exceed 2.5 m in length.
Trap door
Hanger
Cat-walk
boards
Binder
Trimmed ceiling joist
12.3.16 Struts
Figure 12.6 (a) Section through roof trap
Figure 12.5(d): These are 100 ⫻ 50 mm sawn timbers
that support the purlins at about every fourth or fifth
pair of rafters. This arrangement transfers the roof
load to the ceiling joists and, therefore, requires a
load-bearing wall or partition at right-angles to the
joists and somewhere near the mid-span below.
the edges of the trap, to provide an access path
through the roof (usually to the storage tank). A line
of chipboard floor-panels could be used as a modern
alternative.
12.3.17 Straining Pieces
12.3.23 Lay Boards
Figure 12.5(d): These are basically sole plates of
100 ⫻ 50 mm or 100 ⫻ 75 mm section, fixed to the
ceiling joists between the base of the struts. They support and balance the roof thrust and allow the struts
to be set at 90⬚ to the roof slope.
Cripple
rafter
Ridge
board
Ridge
board
12.3.18 Collars
Lay
board
le
ipp
Cr
r
fte
Lay
board
ra
Figure 12.5(d): Collars are 100 ⫻ 50 mm sawn ties,
fixed to each rafter, sometimes used at purlin level to
give extra resistance to the roof-spread.
Common
rafters
12.3.19 Binders
Figure 12.5(d): These are 100 ⫻ 50 mm timbers fixed
on edge to the ceiling joists with skew-nails or modern framing anchors. They are set at right-angles to
the ceiling joists, to give support and counteract
deflection of the joists if the span exceeds 2.5 m.
12.3.20 Hangers
Figures 12.5(d) and 12.6(a): These are 100 ⫻ 50 mm
ties that hang vertically from a rafter side-fixing position near the purlin, to a side-fixing position on the
ceiling joist and the binder, usually close to the struts.
Common
rafter
Figure 12.6 (b) Lay boards
Figure 12.6(b): These are location sole-plates of about
175 ⫻ 25 mm sawn section, laid flat and diagonally on
the ribbed roof structure, to receive the splay-cut feet
of cripple rafters forming a valley. This is a popular
alternative to using valley rafters, as it is stronger and
involves less work.
12.3.21 Roof Trap or Hatch
Figure 12.6(a): The roof trap is a trimmed and lined
opening in the ceiling joists, with a hinged or loose
trap door. It provides access to the roof void for maintenance of storage tank and pipes, etc.
12.3.22 Cat Walk
Figure 12.6(a): This consists of one or two 100–150 ⫻
25 mm sawn boards fixed across the ceiling joists from
12.3.24 Eaves
Figure 12.6(c): This is the lowest edge of the sloping
roof, which usually overhangs the structure from as little as the fascia-board thickness up to about 450 mm.
This is measured horizontally and is known as the
eaves’ projection, which may be open (showing the ends
of the rafters on the underside, as a feature) or closed
(by the addition of a soffit board).
Roof Components and Terminology
137
12.3.29 Tilting Fillets
Cradling
Eaves
Sprocket
piece
Fascia board
Soffit board
Eaves’
projection
Figure 12.6 (c) Fascia, soffit and eaves
Vent
12.3.25 Fascia Board
Figure 12.7 (a) Cradling
Figure 12.6(c): The fascia is a prepared board of about
ex. 175 ⫻ 25 mm, fixed with 75 or 100 mm cut, clasp
or oval nails to the plumb cuts of the rafters at the
eaves. It provides a visual finish, part of the closing-in
at the eaves, and a fixing board for the guttering.
Common rafter
Tilting
fillet
12.3.26 Soffit Board
Figure 12.6(c): This can be fixed to cradling brackets
on the underside of closed eaves, as illustrated separately in Figure 12.7(a), between a groove in the fascia
board and the wall. This board can be of 9–12 mm
WBP exterior plywood or non-asbestos fibreboard.
The soffit of the eaves must provide cross-ventilation,
equivalent in area to a continuous gap of 10 mm width
along each side of the roof.
12.3.27 Cradling
Figure 12.7(a): Cradling is a traditional way of providing wall-side fixing points for the soffit board. Purposemade, L-shaped brackets made up from 50 ⫻ 25 mm
sawn battens, with simple half-lap corner joints clenchnailed together, are fixed to the sides of the rafters with
63 mm round-head wire nails.
12.3.28 Sprocket Pieces
Figures 12.7(a) and (b): These are long wedge-shaped
pieces of ex. rafter material, fixed on top of each rafter
at the eaves to create a bell-shape appearance or upward
tilt to the roof slope. As shown in Figure 12.7(b), this is
also achieved by fixing offcuts of rafter to the rafter
sides. Apart from aesthetic reasons, this is done to
reduce a steep roof slope, in order to ease the flow of
rainwater into the guttering.
Sprocket
piece
Figure 12.7 (b) Sprocket piece and tilting fillet
Figures 12.7(b) and (c): Tilting fillets are timber battens of triangular-shaped cross-section fixed behind
the top of a raised fascia board to give it support. The
fascia board has been raised primarily to tilt and close
the double-layered edge of the tiles or slates, but the
increased depth of board also helps the plumber create
the necessary falls in the guttering. Tilting fillets are
also used in other places, such as on the top edges of
valley boards (Figure 12.7(c)) and back gutters, etc.
12.3.30 Valley Boards
Figure 12.7(c): Traditionally, 25 mm sawn boards were
used to form a gutter in the valley recess, each board
being about 225 mm wide. A tilting fillet was fixed at
the top edge of each board, ready to be included in the
lining of the valley with sheet lead.
138
Constructing Traditional and Modern Roofs
the wall, a soffit board will be required, involving a
boxed-shape at the eaves on each side.
Tile
Lead lined
valley gutter
12.3.34 Tile or Slate Battens
Cripple
rafter
Roofing
felt
Tilting fillet
Valley boards
Tile
Valley rafter
These are usually 38 ⫻ 18 mm, but can be 38 ⫻ 25 or
50 ⫻ 25 mm sawn, tanalized (pressurized preservative
treatment) battens fixed at gauged spacings on top of
the lapped roofing felt. The fixing of these battens is
normally done by the slater and tiler, not the carpenter.
12.3.35 Framing Anchors
Figure 12.7 (c) Valley gutter
12.3.31 Glass-reinforced Plastic
Valleys
Modern valley linings are now manufactured to a
preformed shape, using glass-reinforced plastic
(GRP). The moulded shape includes a double-roll on
each edge to simulate the weathering-upstand of a
traditional tilting fillet. These edges should rest on
continuous tiling battens, fixed to the cripple rafters;
valley boards are not needed.
Framing anchor truss clips
Figure 12.7 (e) Framing anchors
12.3.32 Verge
Verge
Verge
Barge boards
Figure 12.7(e): Galvanized steel framing anchors of
various designs for various situations may be used to
replace traditionally nailed fixings in certain places.
The one shown here replaces skew-nailing of the ceiling joist to the wall plate. The recommended fixings to
be used (in every hole of the framing anchor) are 3 mm
in diameter by 30 mm long sherardized clout nails.
12.4 BASIC SETTING-OUT
TERMS
12.4.1 Introduction
Figure 12.7 (d) Verge and barge boards
Figure 12.7(d): This is the edge of a roof on a gable
end. It may have a minimum tile-projection and no
barge boards, or a greater projection (about
150–200 mm) with barge boards and soffit boards to
the sloping underside.
12.3.33 Barge Boards
Figure 12.7(d): These are really fascia boards inclined
like a pair of rafters and fixed to a small projection of
roof at the gable-end verges. When projecting from
All the bevels and lengths in roofing can be worked out
by various methods – all of which are based on the
principles of geometry. Although the actual method of
using drawing-board geometry is not practical in a site
situation, it is given in Figure 12.9 as an introduction to
understanding how the various bevels and lengths are
found.
First, as illustrated in Figure 12.8, the following
basic setting-out terms must be appreciated in relation
to the sectional view through the pitched roof.
12.4.2 Span
This is an important distance measured in the direction
of the ceiling joists at wall-plate level, from the outside
Basic Setting-out Terms
BRL
139
Rise
BRL
Pitch
BRL minus
half ridgethickness
measured
horizontally
Run
Plumb
cut
Basic rafter
length
Notional
pitch line
Rise
Run = 1/2 Span
Pitch
Span = O/A wall plates
BRL
2/3
BRL plus total
Eaves’
projection, A + B
Minus
fascia
thickness
1/3
Backing line
Birdsmouth
Plumb
cut
B
Seat cut
A
of one wall plate to the outside of the other, i.e. overall
(O/A) wall plates.
12.4.3 Run
For the purpose of reducing the isosceles roof-shape
to a right-angled triangle with a measureable baseline, the span measurement is divided by two to produce what is known as the run.
Figure 12.8 Basic setting-out terms
(BRL ⫽ basic rafter length)
sides of the rafters, from the outside arris of the wall
plates.
12.4.5 Pitch
This is the degree angle of the roof slope. The known
rise and the run gives the pitch angle and the basic
rafter length – or the known pitch angle and the run
gives the rise and the basic rafter length.
12.4.6 Backing Line
12.4.4 Rise
This represents the perpendicular of the triangle,
measured from wall-plate level up to the apex of
the imaginary hypotenuse or notional pitch lines
running at two-thirds rafter-depth, through the
This is an important plumb line marked at the base of
the setting-out rafter (pattern rafter), marked down
two-thirds of its depth to the top of the birdsmouth
cut, acting as a datum or reference point for the rafter’s
length on one side and the total eaves’ projection on
the other.
140
Constructing Traditional and Modern Roofs
12.4.7 Birdsmouth
This is a notch cut out of the rafter to form a seating
on the outside edge of the wall plate.
12.5.3 Hip Edge Cut
12.5 GEOMETRICAL SETTINGOUT OF A HIPPED ROOF
12.5.1 Bevels and Length of Common
Rafter
BRL
K
C
U
Section
through
roof
T
BRL
Rise
Pitch
A
L
B
D
Run
Span
A⬘
R
Q
V
O
S
P
Rise
I
F
W⬘
J
G
Z
Y
A⬙
W⬙
12.5.4 Jack (and Cripple) Rafter
Bevels and Lengths
Figure 12.9: With radius CA, equal to basic rafter
length, describe an arc from A to K. Project K down
vertically to form line LM. Join L to E to give an elevated, true shape of roof side. Draw single lines to
represent rafters at 400 mm (scaled) centres: angle
LEN ⫽ jack/cripple edge cut. (The jack/cripple side
cut is the same as the common rafter plumb cut.) Line
OP ⫽ the basic length of the first jack rafter; line
QR ⫽ the second diminishing jack rafter.
Figure 12.9: The perpendicular line SP, of the rightangled triangle RSP, is equal to the constant diminish
of the jack (or cripple) rafters.
12.5.6 Purlin Bevels
Plan of
roof
X
Figure 12.9: Draw line HI, parallel to EG at any distance from E; then draw line IJ, equal to distance EH,
at right-angles to B⬘I. Draw line JG: angle JGI is the
edge cut.
12.5.5 Diminish of Jack (and Cripple)
Rafter Lengths
Hip plan =
hip run
H
E
Rise
M
B⬘
BHRL
N
length to the rise at CD. Join G to B⬘: angle EB⬘G ⫽
seat cut, angle B⬘GE ⫽ plumb cut, line B⬘G ⫽ basic
hip rafter length (BHRL).
B⬙
Figure 12.9 Geometry for hipped roof
Figure 12.9: Draw triangle ABC (section through roof )
where: AB ⫽ span, AD ⫽ run (half span), CD ⫽ rise,
angle DAC ⫽ seat cut, angle ACD ⫽ plumb cut, line
AC or CB ⫽ basic rafter length (BRL).
12.5.2 Bevels and Length of Hip
Rafter
Figure 12.9: Draw plan of roof, showing two hipped
ends (these being always drawn at angles of 45⬚ in
equal pitched roofs), denoted as A⬘E, B⬘E and A⬙F,
B⬙F. Now, at right angles to B⬘E, draw line EG, equal in
Figure 12.9: Angle QLR, on the elevated plan
view ⫽ purlin edge cut. The purlin side cut is developed within the sectional view through the roof. With
compass at D and CB as a tangent at T, describe an
arc to cut CD at U, and join U to B: angle
DUB ⫽ purlin side cut.
12.5.7 Dihedral Angle or Backing
Bevel
Figure 12.9: This is for the top edge of hip boards and
might only be used nowadays if the roof – on a less
cost-conscious, quality job – were to be boarded or
sheathed with 12 mm plywood, prior to felting, battening and slating or tiling. On the plan view, establish
triangle A⬙VF, as at B⬘GE. Draw a 45⬚ line at any
point, marked W⬘W⬙. With compass at X and A⬙V as
a tangent at Y, describe an arc to cut A⬙F at Z. Join Z
to W⬘ and W⬙: angle W⬘ZX or XZW⬙ is the required
backing bevel.
Roofing Ready Reckoner
12.6 ROOFING READY
RECKONER
out from the tables – which show a given measurement for the hypotenuse of the inclined rafter, in relation to base measurements of metres, decimetres and
millimetres (or, in separate tables given, feet, inches
and eighths of an inch) contained in the run of the
common rafter.
12.6.1 Introduction
The first practical method to be considered for finding
the bevels and lengths in roofing, is by reference to a
small limp-covered booklet entitled Roofing Ready
Reckoner by Ralph Goss, published by Blackwell Scientific Ltd, ISBN 0632021969. The tables are given separately in metric and Imperial dimensions and are quite
easy to follow, once a few basic principles have been
grasped.
12.6.3 Determining Run and Pitch
To use this method, first the span of the roof must be
measured from the bedded wall-plates and halved to
give the run. Also, the pitch must be known – and if
not specified, should be taken, with the aid of a protractor, from the elevational drawings.
12.6.4 Example Workings Out
12.6.2 Choice of Tables
As an example, take a hipped roof of 36⬚ pitch, with a
span of 7.460 m. Halve this to give a run of 3.730 m.
Then, referring to the tables taken from the booklet
and illustrated here in Figure 12.10, work out the
lengths of the common rafters and the hip rafters.
Figure 12.10: The tables cover a variety or roof pitches
up to 75⬚, giving the various bevels required and the
diminish for jack rafters. Basic rafter lengths (BRL)
and basic hip rafter lengths (BHRL) must be worked
Information
required:
Pitch
Span
Run
36°
Span = 7.460 m
Run = 3.730 m







Bevels = common rafter seat cut = 36°
Jack and common rafter plumb cut = 54°
Hip or valley rafter seat cut = 27°
Hip or valley rafter plumb cut = 63°
Jack rafter edge cut = 39°
Purlin edge cut = 51°
Purlin side cut = 59.5°
Set on
sliding
bevel with
protractor
supplied
in booklet
Table for 36° pitch
Run of rafter
Rafter length
Hip length
0.1
0.124
0.159
0.2
0.247
0.318
0.3
0.371
0.477
0.4
0.494
0.636
0.5
0.618
0.795
0.6
0.742
0.954
0.7
0.865
1.113
Common rafter length =
BRL – 1/2 ridge thickness
+ eaves’ projection
0.9
1.112
1.431
1.0
1.236
1.590
BHRL**
cL
Common rafter
run
0.8
0.989
1.272
Hip
rafter
Common
rafter
BRL*
141
cL
Common rafter run
used for hip rafter run
Hip rafter length = BHRL – 1/2 diagonal
ridge thickness + diagonal eaves’
projection
Figure 12.10 Roofing
Ready Reckoner
142
Constructing Traditional and Modern Roofs
Common Rafter
Length of common rafter for 1 m of run ⫽ 1.236 m
Length of common rafter for 3 m of run ⫽ 3.708 m
Length of common rafter for 0.7 m of run ⫽ 0.865 m
Length of common rafter for 0.03 m of run ⫽
0.0371 m
Length of common rafter for 3.730 m of run ⫽
4.6101 m
Therefore the basic rafter length (BRL*) ⫽ 4.610 m
Speedier Working Out
It must be mentioned that a speedier mathematical
method would be to multiply the total common rafter
run by the 1 m run-of-rafter figure given in the booklet’s tables, i.e.:
Length of hip rafter for 0.7 m of run ⫽ 1.113 m
Length of hip rafter for 0.03 m of run ⫽ 0.0477 m
Length of hip rafter for 3.730 m of run ⫽ 5.9307 m
Therefore, the basic hip rafter length (BHRL**) ⫽
5.931 m
Speedier Working Out
This involves multiplying the total common rafter run
by the 1 m run-of-rafter figure given directly under
that column for the length of hip, in the booklet’s
tables, i.e.
3.730 ⫻ 1.590 ⫽ 5.9307 m (call this 5.931 m BHRL)
12.6.5 Jack Rafter Diminish
3.730 ⫻ 1.236 ⫽ 4.610 m ⫽ BRL
Hip Rafter
Length of hip rafter for 1 m of run ⫽ 1.590 m
Length of hip rafter for 3 m of run ⫽ 4.770 m
Information
required: Rafter centres (spacings)
Jack rafters 400 mm centres decrease 494 mm
Jack rafters 500 mm centres decrease 618 mm
Jack rafters 600 mm centres decrease 742 mm
Figure 12.11: Jack and cripple rafters should diminish
in length by a constant amount in relation to the
length of the main rafter (crown or common). The
Roofing Ready Reckoner gives a set of figures for each
different pitch, shown on the same page as the bevels
and tables, to deal with the decrease according to the
spacing of the rafters. Assuming rafters to be spaced at
400 mm centres on the 36⬚ pitched roof described in
the text for Figure 12.10, then the diminish, as illustrated in Figure 12.11, would be 494 mm.
12.6.6 Imperial-dimensioned Tables
True view
of hipped
end
Diminish
Crown
rafter
Figure 12.11 Jack rafter diminish for 36⬚ pitch
Diminish
Figure 12.12: As a comparison – and perhaps as an
alternative for any diehards in the industry, still using
feet and inches – the following example is given, using
the imperial tables in the Ready Reckoner, expressed in
feet, inches and eighths of an inch. Again, take a
hipped roof of 36⬚ pitch, but with a span of 24 ft 5 in
(24 feet, 5 inches). Halve this to give a run of 12 ft
2 -21 in. Then, referring to the tables taken from the
Figure 12.12 Imperial tables
Metric Rafter Square
booklet and illustrated here, work out the lengths of
the common rafters and hip rafters as follows:
⫽ 12 ft 4 -83 in
Length of common rafter for 2 ft of run
⫽ 2 ft 5 -58 in
Length of common rafter for 2 in of run
⫽ 2 -12 in
1
2
Length of common rafter for - in of run
40
Tongue
450
Length of common rafter for 10 ft of run
143
⫽ -58 in
Scale of pitches
Length of common rafter for 12 ft 2 -12 in of run ⫽ 15 ft 1 -18 in
Length of hip rafter for 10 ft of run
⫽ 15 ft10 -43 in
Length of hip rafter for 2 ft of run
⫽ 3 ft 2 -18 in
Length of hip rafter for 2 in of run
⫽ 3 -18 in
Length of hip rafter for -12 in of run
⫽ -43 in
1
2
Length of hip rafter for 12 ft 2 - in run
⫽ 19 ft 4 - in
3
4
12.6.7 Conclusion
It must be realized that, because of the involvement
with fractions of an inch, the imperial method of
working out lengths of rafters and hips, unlike the
metric method, does not offer a speedier working out.
However, it can be done by using inches as the basic
units, providing the fractions of an inch are changed
to decimals, whereby -12 in ⫽ 0.5, -14 in ⫽ 0.25, -18 in ⫽
0.125, 1–16 in ⫽ 0.0625 and 3–12 in ⫽ 0.03125.
Therefore, on the last working out, the pitch was
36⬚, the common rafter run was 12 ft 2-12 in. Converted
to inches and decimals, this would become 146.5 in.
This figure is then multiplied by 1.236 (the 1 m runof-rafter figure for 36⬚), therefore:
50
Blade
620
Figure 12.13 Metric rafter square model No. 390
or 390B
12.7.2 Protractor Facility
The various settings for different roof bevels – which
are not easy to remember – are usefully given on the
faces of the tongue. These are related to traditional
settings, based on geometric principles. The main
innovation, though, is that the square has a protractor
facility in the form of a scale of pitches on the inner
edge of the blade, enabling any pitch angle up to 85⬚
to be set up quickly and easily.
12.7.3 Common Rafter Plumb and
Seat Cuts
146.5 ⫻ 1.236 ⫽ 181.074 in
⫽ 15 ft 1.074 in
Therefore the length of common rafter for a 12 ft 2-12 in
run is 15 ft 1–116 in. The –116 in less than the previous
working out is insignificant in roofing.
12.7 METRIC RAFTER SQUARE
35° A
68° B
(a)
12.7.1 Introduction
Figure 12.13: The next method to be considered
involves the use of a traditional instrument known
as a steel roofing square, now metricated and called
the metric rafter square. The one referred to here is
manufactured by I & D Smallwood Ltd, and comes
with an explanatory booklet on its use. Other, similar
rafter squares on the market, adequate for the job, do
not have the protractor facility incorporated in the
Smallwood square, which is personally preferred by the
author. The booklet, which is well illustrated, clearly
explains the elements of roofing and the application of
the square.
Hip plumb cut
Hip seat cut
35°
B
(b)
H.V. run
66° to 85°
A
H.V. run
0.5° to 66°
Figure 12.14 (a) Using protractor facility to find common
rafter plumb and seat cuts; (b) finding hip bevels
144
Constructing Traditional and Modern Roofs
Figure 12.14(a): By using the protractor facility to set
up the pitch, common-rafter plumb and seat cuts are
quickly found. This is achieved by using a commonrafter-run point A, set at 250 mm on the inner edge of
the tongue, as illustrated, and by rotating the square
until the degree figure for the roof pitch registers on
the inner edge of the blade. This works for pitch
angles up to 66⬚. Should greater angles than this be
required, then a common-rafter-run point B, set at
50 mm on the inner edge of the tongue, is used in
relation to the scale of pitches on the blade. This will
give angles from 66⬚ to 85⬚.
12.7.4 Hip (or Valley) Rafter Plumb
and Seat Cuts
Figure 12.15: To increase the square’s use from an
instrument to a working tool, stair gauge fittings, as
illustrated, are an available option for this – or any
roofing square. The fittings are attached to the square’s
edges to act as stops, for setting and marking repetitive bevels, thus avoiding the use of a separate carpenter’s bevel.
12.8 ALTERNATIVE METHOD
FOR THE USE OF THE METRIC
RAFTER SQUARE
12.8.1 The Scaled Method
Figure 12.14(b): These bevels are also found by using
the protractor facility related to the roof pitch. This is
achieved by using a hip or valley-rafter-run point,
marked ‘H.V. run’ on the square, set at 354 mm on the
inner edge of the tongue and, by rotating the square
until the degree figure for the roof pitch registers on
the inner edge of the blade. This will give hip or valley
plumb and seat cuts for roofs up to 66⬚. Should the
roof be steeper than this, then a hip or valley-rafterrun point, set at 71 mm on the inner edge of the
tongue for roofs from 66⬚ to 85⬚, is used in relation to
the scale of pitches on the blade.
A method used traditionally for its speed and simplicity
in finding the main rafter lengths and bevels was known
as the scaled method. This lends itself easily to metrication, from its original use in Imperial dimensions –
whereby inches represented feet and twelfths-of-aninch represented inches. Figure 12.16 should help in
grasping this method, by visualizing the roofing square
within the roof, either by imagining the square scaled up
to roof-size or the roof scaled down to square-size.
12.7.5 Common and Hip (or Valley)
Rafter Lengths
Figure 12.17: These American pattern stair gauge fittings (also illustrated on the sides of the square in
Figure 12.18(b)) are almost an essential requirement –
if you can obtain them – for this particular roofing
method. This is because they relate accurately to preset measurements on the edges of the blade or tongue
of the square; they also enable very accurate readings
of hypotenuse measurements to be made.
As the name of these fittings implies, they were
originally meant to be used on the square for setting
As is normal practice, these rafter lengths are worked
out in relation to the run. Some figures for this are
given on both sides of the blade, against the pitch
required, related to a 1 m run. A more definitive set of
figures are given in the booklet, varying from 1⬚ up to
89.5⬚ pitch, in increments of 0.5⬚. Hence, a small and
simple calculation will be necessary, whereby, as with
the Roofing Ready Reckoner, the total common rafter
run is multiplied by the 1 m run-of-rafter figure given
on the blade or in the booklet, there being, as before,
one figure for common-rafter lengths and another for
hip (or valley) rafter lengths.
12.8.2 Stair Gauge Fittings
(American Pattern)
Rise
12.7.6 Stair Gauge Fittings (British
Pattern)
C/R run
Figure 12.15 Stair gauge fittings model No. 385
Hip run
Figure 12.16 Visualizing the square within the roof
(C/R ⫽ common rafter)
Alternative Method for the Use of the Metric Rafter Square
145
32.5°
Figure 12.17 American-pattern stair-gauge fittings
out the steps of a staircase or the shuttering for concrete
stairs – a use for which, of course, they can still be put.
A
(a)
12.8.3 Finding the Rise
Figure 12.18(a): With the scaled method, it will be
necessary to determine the rise before proceeding further. The key to this is the protractor facility, which
will simplify the task. First, use the square as already
described in the text for Figure 12.14, by laying it on a
straight piece of rafter or straightedge material, relating to common-rafter-run point A on the inside edge
of the tongue and – in this example – 32.5⬚ pitch on
the inside edge of the blade. Mark the bottom, outer
edge of the tongue with a marking knife, chisel or a
sharp pencil. This will give the seat cut and, being
greater in length on this shallow pitch than the plumb
cut would be on a given width of straightedge material, the plumb-cut mark available against the blade
will not be needed.
12.8.4 Common Rafter Length, Plumb
and Seat Cuts
Figure 12.18(b): The next step is to attach a stair gauge
fitting to the outer edge of the blade, set carefully at,
say, 310 mm, representing a scaled run of roof of
3.100 m. Line up the blade to the previously found seat
cut bevel marked on the straightedge, as illustrated,
then carefully attach the other stair gauge fitting to the
outer edge of the tongue against the straightedge. This
will produce the scaled rise at 198 mm. These settings
determine the plumb and seat cuts and provide a scaled
measurement of the common rafter length. The scale
used is one-tenth full size (1:10) and is easily achieved
by moving the decimal point by one place:
3.100 m run divided by 10 ⫽ 0.310 mm on the blade
0.198 mm on the tongue times 10 ⫽ 1.980 m rise
Common rafter
length measures
368 mm (3.680 m)
Rise found
to be 198 mm
(1.980 m)
C/R run
3.100 m set at
310 mm
(b)
Figure 12.18 (a) First step to finding the rise by scaled
method; (b) second step to find the rise, bevels and
length
The scaled measurement of the rafter length on the
hypotenuse – measured between the sharp arrises of
the stair gauge fittings – is also brought up to size by
multiplying by 10, i.e. 0.368 mm ⫻ 10 ⫽ 3.680 m.
12.8.5 Finding the Hip-rafter Run
Figure 12.19: To find the hip rafter length, first find
the hip rafter run. As this represents – in an equal
pitched roof – a 45⬚ diagonal line in plan, contained
within the run of the common rafter and the run of
the crown rafter, forming a square, it follows that the
scaled common-rafter run, set on both the blade and
the tongue, as illustrated, gives the scaled measurement of the hip run at 45⬚ on the hypotenuse.
146
Constructing Traditional and Modern Roofs
Figure 12.21: This equals the scaled hip length on the
blade and the scaled hip run on the tongue. As illustrated, the bevel is found on the blade. This is applied
to the edges of the hip plumb cut and enables the hips
to fit into the heads of the crown rafter and the first
commons, against a saddle board – or, alternatively, to
fit against each other and the saddle board. A simpler
way of finding the edge bevel, is to measure and mark
half the hip’s thickness x in from the second plumb
cut each side. This gives the three points on the top
edge for marking the edge bevels. To understand this
more fully, see ‘setting out hip rafters’ after the
Roofmaster method (page 152).
Gives hip run of
438 mm (4.3800 m)
C/R run
310 mm
C/R run 310 mm
Figure 12.19 Settings to find the hip run
12.8.6 Hip Rafter Length, Plumb and
Seat Cuts
12.9.2 Hip Backing Bevel (Dihedral
Angle)
Gives hip length
of 481 mm (4.810 m)
Rise
198 mm
P/C
S/C
Rise
Hip length
Figure 12.22 Hip backing bevel
Hip run 438 mm
Figure 12.20 Hip rafter length, plumb and seat cuts
Figure 12.20: Now alter the position of the stair gauge
fittings and set the scaled hip run on the blade, and
the scaled rise on the tongue, as illustrated. This will
give the scaled hip rafter length, the plumb cut (P/C)
and the seat cut (S/C).
Figure 12.22: This equals the scaled hip length on the
blade and the scaled rise on the tongue. As illustrated,
the bevel is found on the tongue. This was used traditionally when the roof was to be boarded and was
applied by planing the top edge from both sides to a
top centre line.
12.9 BEVEL-FORMULAS FOR
ROOFING SQUARE
12.9.3 Jack or Cripple Side
(Plumb) Cut
12.9.1 Hip Edge Cut
This is the same formula as for the common rafter
plumb cut, with the scaled common rafter run set on
the blade, the scaled rise on the tongue and the
required bevel found on the tongue.
Hip length
Hip
run
x
1/2
x=
hip
thickness
Figure 12.21 Hip edge cut
x
12.9.4 Jack or Cripple Edge Cut
Figure 12.23: This combines with the above cut to
make a compound angle to fit against the hip or valley
rafters. The formula equals the scaled common-rafter
length on the blade and the common rafter run on the
tongue. The bevel, A, is found on the blade.
Roofmaster Square
147
12.9.7 Purlin Lip Cut
E/C
A
Purlin
side cut
C/R length
1/2 hip
thickness
90°
B
C/R run
Figure 12.25 Purlin lip cut (E/C ⫽ edge cut)
Figure 12.23 Jack edge cut (bevel A) and purlin edge
cut (bevel B)
12.9.5 Purlin Edge Cut
Figure 12.23: This bevel is applied to the surface that
the underside of the rafters rest on, at the junction of
the hips or valleys, to form a mitred edge against the
sides and under the centre of the hip or valley rafters.
The formula is the same as for the jack or cripple edge
cut, except that the required bevel B is found on the
tongue.
12.9.6 Purlin Side Cut
Figure 12.24: This combines with the above cut, to
complete the mitred faces against and under the hips
or valley rafters. The formula equals the scaled common rafter length on the blade and the rise on the
tongue. The bevel required is found on the tongue.
Figure 12.25: As illustrated, this is simply marked at
90⬚ to the purlin side cut in relation to the amount of
hip projection below the rafters.
12.9.8 Jack or Cripple Rafter
Diminish
Figure 12.26: As illustrated, this is found in two stages.
First, by setting the jack edge-cut formula on the square
and marking this – against the edge of the blade – on
a straightedge. Then by sliding the blade along the
mark until the projecting tongue registers the commonrafter centres at a half full-size scale (say 400 mm centres divided by 2 ⫽ 200 mm on the tongue). The
measurement now showing on the projecting blade
will be equal to a half full-size scale of the diminish.
12.9.9 Bevel Formulas
Table 12.1 on page 148 gives bevel formulas in quick
reference style.
12.10 ROOFMASTER SQUARE
12.10.1 Introduction
Rise
Figure 12.27: The final method to be considered as an
alternative to the roofing square and the Roofing Ready
Reckoner, is the innovative, recently re-marketed tool
(or instrument) known as the Roofmaster. It consists
of an anodized aluminium blade, resembling a 45⬚
set square, engraved with easy-to-read laser-etched
C/R length
Figure 12.24 Purlin side cut
Rl
un
Rr
C/
Set 1/2 scale
C/R centres
C/
Mark
blade
First stage
Gives 1/2 scale
diminish
en
gth
Slide along
mark
Second stage
Figure 12.26 Jack rafter diminish
148
Constructing Traditional and Modern Roofs
Table 12.1 Bevel formulas
Component
Required bevel
Blade setting
Tongue setting
Side for marking
Common rafter
Common rafter
Hip rafter
Hip rafter
Hip rafter
Hip rafter
Hip rafter
Jack rafter
Jack rafter
Purlin
Purlin
Lay board
Lay board
plumb cut
seat cut
run of hip
plumb cut
seat cut
edge cut
backing bevel
side cut
edge cut
edge cut
side cut
plumb cut
seat cut
C/R run
C/R run
C/R run
hip run
hip run
hip length
hip length
C/R run
C/R length
C/R length
C/R length
C/R length
C/R length
rise
rise
C/R run
rise
rise
hip run
rise
rise
C/R run
C/R run
rise
C/R run
C/R run
tongue
blade
hypotenuse measurement
tongue
blade
blade
tongue
tongue
blade
tongue
tongue
blade
tongue
necessary, to determine the different bevels, such as
common-rafter plumb and seat cuts, hip-rafter plumb
and seat cuts, purlin side and edge cuts, jack and cripple rafter plumb and edge cuts, etc.
12.10.3 Main Features
Three main features are engraved on each side of the
blade as follows.
●
●
●
Figure 12.27 Roofmaster square (Artistic representation only)
figures and markings on each face side. Attached to
the blade is a pivoting and lockable, double-sided
fence (or arm), through which the blade is slid when
locking the fence to a required setting. The instrument comes with a booklet which is well illustrated
and clearly explains the application and use.
12.10.2 Basic Concept
The basic concept of this revolutionary square, is that
the only knowledge needed to access all the different
bevels required in the cutting of a roof, is the pitch
angle. If, for example, the pitch to be used is 35⬚, that
would be the only reference required to set up the
Roofmaster as many times as necessary, and when
A set of separate, graduated segmental arcs, each
one is referenced to a specific roof member and calibrated to give the required bevel, which is obtained
simply by setting the adjustable fence to the
required pitch angle numbered on the selected arc.
Information panels on each face side of the blade
indicate which edge to mark for the selected angle
cut. This valuable facility eliminates yet another area
of confusion associated with other roofing squares.
Tables for length of common, hip and valley rafters
per metre of run, radiating around the remaining
segmental arcs, are calibrated to line up the multiplier figure for use in obtaining the true or basic
length, obtained simply – once again – by setting
the adjustable fence to the required pitch angle
numbered on the pitch-angle arc.
12.10.4 Handling the Roofmaster
Figure 12.28: As with other roofing squares, the angles
required will always be acute angles contained within
the right-angled triangle formed with this tool, by the
right-angle of the blade and the varying position of the
adjustable fence, acting as the triangle’s hypotenuse. As
illustrated, the setting edge of the fence, which is
clearly marked, always butts against the edge of the
roof member.
Roofmaster Square
149
12.10.6 Finding Cutting Angles
To apply the plumb and seat cuts to a common rafter for
a roof to be pitched, say, at 35⬚, first, select the arc designated for common-rafter cuts of 16–45⬚; second, lock the
adjustable arm on number 35; third, hold the tool with
the setting edge of the fence firmly against the rafter
material; and finally mark the edges indicated by the
information panels on the blade, for the required cuts.
Note that this sequence of operations is carried out
on each relevant arc to obtain the different cut-angles
for all of the roof members.
Figure 12.28 Acute angles required *
12.10.5 Reverse and Opposite
Marking-positions
Figure 12.29: An important operational fact to realize
is that once the fence has been locked into the
required position, the Roofmaster can be used on
opposite side-edges of the timber to mark the same
bevel (Figures 12.29(a) and (b)) or, if necessary, can be
reversed (turned over) to give either left- or righthand cuts (Figure 12.29(c)).
12.10.7 Rafter Lengths
Figure 12.30: The common rafter and hip or valley rafter
lengths per metre of run are engraved on each side of the
blade, for roof pitches of 16–45⬚ on one side and 45–75⬚
on the other. To obtain the true or basic length of one of
these rafters, the adjustable arm must be set to the correct pitch angle figure on the common-rafter arc. The
two sets of table numbers now displayed – and indicated
by reference headings – along the setting edge of the arm
will be the common rafter length per metre of run and
the hip or valley length per metre of run. When the figures shown are multiplied by the common rafter run, the
true or basic lengths of rafters will be obtained.
Figure 12.29 Reverse and
opposite marking-positions
Figure 12.30 Rafter lengths per
metre of run
150
Constructing Traditional and Modern Roofs
12.10.8 Example Working Out
Figure 12.30: Assume a roof pitch of 35⬚ with a span
of 6.486 m.
1. Set the arm to number 35 on the common rafter arc.
2. Record the table numbers displayed under reference
headings on the adjustable arm, thus:
common rafter ⫽ 1.221; hip or valley rafter ⫽ 1.578
3. Divide the span by 2 to find common rafter run:
6.486 ⫼ 2 ⫽ 3.243 m
4. True length of common rafter is
1.221 ⫻ 3.243 ⫽ 3.959 m
True length of hip or valley rafters is
1.578 ⫻ 3.243 ⫽ 5.117 m
12.11 SETTING OUT A
COMMON (PATTERN) RAFTER
12.11.1 Technique (for any Roofing
Tool or Bevel)
Figure 12.31(a): Select a piece of rafter material
which is straight and without twists and mark a
common-rafter plumb cut A at the top of the rafter’s
face side, representing the centre of the ridge board.
Next, mark another plumb cut B into the body of the
rafter, at half the ridge-board thickness measured at
right-angles to plumb line A, representing the actual
plumb cut against the ridge board. Transfer these
lines squarely across the top edge and make a shallow
saw cut on the waste side of the edge-line (Figure
12.31(b)) to provide an anchorage for the hook of a
tape rule.
12.11.2 Marking the True or Basic
Length
Figure 12.31(c): Place the hook of the tape rule into
the saw cut on the rafter’s top edge, run the rule
down to the eaves’ area and mark the common rafter
length – after having worked this out from one of
the methods previously covered. Square this mark
across the top edge and, from this point, mark
another plumb cut C. This important plumb cut is
known as the backing line, which is now measured
for depth, divided by three and marked down twothirds to indicate the corner of the birdsmouth D,
from which point the common rafter seat-cut is
marked.
BRL
90°
To be
cut here
C
BRL
D
A
B
(a)
(b)
(c)
BRL
+E
+F
(d)
Figure 12.31 (a) First step; (b) second step;
(c) third step; (d) fourth step
Setting Out a Crown (or Pin) Rafter
12.11.3 Working out the Eaves’
Projection
Figure 12.31(d): Finally, the rafter must carry on down,
from the backing line, across the outer skin of brickwork E, to a distance measured horizontally from the
face of the wall and known as the eaves’ projection F.
As referred to earlier (Figure 12.8, showing basic
setting-out terms), the total projection horizontally
equals E ⫹ F minus the thickness of the fascia board.
The concealed projection E is equal to the wall-thickness, minus wall plate. The visible eaves’ projection F
can be scaled from the elevational drawing showing the
roof. For example, assume a wall of 275 mm, a visible
eaves’ projection of 200 mm, a wall plate 100 mm wide
and a fascia board 20 mm thick. The sum would be
E ⫽ 275 ⫺ 100 ⫽ 175 mm
F ⫽ 200 ⫺ 20 ⫽ 180 mm.
151
Offcut
Pattern
rafter
First off
pattern
Lay rafters on ground
then check and adjust to
correct span – then check
ridge-board plumb cuts
(a)
First off
Pattern
Could be
wrong span,
rafters too long
or wrong plumb cut
Total eaves’ projection ⫽ 175 ⫹ 180 ⫽ 355 mm.
12.11.4 Adding the Eaves’ Projection
With the metric rafter square, this value (355 mm) can
be set on the tongue while the blade is lined up to the
backing-line plumb mark, the square being slid up or
down until the blade lines up precisely and the 355 mm
point on the tongue can be marked at the end of the
rafter to become the plumb cut for the fascia board.
With the Roofmaster or the Roofing Ready Reckoner,
the sum of 355 mm can be used as the figure for the run
of the total projection, multiplied by the common-rafter
table figure for, say 35⬚, i.e. 0.355 ⫻ 1.221 ⫽ 0.433 m
(433 mm), to be measured down the top edge of the
rafter, from the backing line to the top of the fasciaboard plumb cut. If a soffit board is to be used, this
plumb cut is usually marked down a half to two-thirds
its depth and a seat cut established at this point.
12.11.5 Cutting and Checking the
First Pair
Figure 12.32: The pattern rafter just marked should be
double-checked (a wise trade saying is ‘check twice, cut
once’), as this first rafter is used for marking out the
rest. Next, square the face marks across any edges not
yet done. Cut all the bevels carefully, including the
birdsmouth and write the word ‘PATTERN’ boldly on
the face of the rafter. Next, only one common rafter
should be marked and cut from the pattern, the pair
laid on the ground with an offcut of ridge board
between the plumb cuts and a tape rule stretched across
the birdsmouth-cuts to check the span. If only slightly
out, adjust the rafters to the correct span, then check
the plumb cuts for a good fit against the ridge-board
Pattern
First off
Could be
wrong span,
rafters too short
or wrong plumb cut
(b)
Figure 12.32 (a) Cutting and checking first pair;
(b) possible error
offcut. If satisfactory, the rest of the common rafters
may be cut, keeping any cambered or sprung edges on
top. If unsatisfactory, go through a checking procedure,
as suggested in Figure 12.32(b).
Note that some carpenters leave the marked fascia
plumb-cuts to be checked with a string line after all of
the rafters have been fixed and then they cut them off
in situ, for better alignment. However, if a soffit seatcut is required, this is very awkward to cut in situ and
should be done at the initial cutting stage.
12.12 SETTING OUT A
CROWN (OR PIN) RAFTER
12.12.1 Slight Difference
The procedure for setting out a crown rafter is identical
to that for setting out a common rafter, except that
152
Constructing Traditional and Modern Roofs
instead of deducting half the ridge-board thickness from
the first plumb cut – as described in the common-rafter
text to Figure 12.31(a) – half the common-rafter thickness is deducted. Therefore, the first plumb cut A
represents the geometrical centre of the hip end and the
second plumb cut B, again measured into the body of
the rafter, at right-angles to the plumb line, represents
the actual plumb cut against the saddle board.
of the rafter on each side, measured at right angles to
line B and equal to half the hip’s thickness. Where
these plumb lines meet the top edge opposite each
other, together with the centre-mark of edge-line B,
they present the three points for marking the hip edge
cut bevels, as illustrated.
12.13.2 Marking the True or
Basic Length
12.13 SETTING OUT A HIP
RAFTER
BHRL
E
12.13.1 Technique
E
Saw cut
1/2 hip
2/3 of common
rafter
thickness
D
F
Backing
bevels
A
B
C
Minus 1/2 diagonal thickness of common rafter ∗
Common rafter edge
∗
Figure 12.33 (a) Setting out a hip rafter
Figure 12.33(a): This technique is applicable for any
roofing tool or bevel. First, mark a hip-rafter plumb
cut A at the top of the rafter’s face side, representing
the geometrical centre-point intersection of the hip
end. Next, mark another plumb cut B into the body of
the rafter, measured at right-angles to plumb line A
and equal to half the common rafter thickness measured diagonally at 45⬚, as illustrated. This represents
the arris or sharp edge of the compound-angled
plumb cut. Transfer these lines squarely across the top
edge and make a shallow saw cut on the waste side of
edge-line A, to provide an anchorage for the hook of a
tape rule – and mark the centre of edge-line B to provide the central point for the opposing hip edge cuts.
The simple way of finding this bevel, as explained
previously in the text to Figure 12.21 (bevel formulas),
is to mark another plumb cut C, again into the body
Figure 12.33 (b) Hip with backing bevels
Figure 12.33(b): Place the hook of the tape rule into
the saw cut on the rafter’s top edge, run the rule down
to the eaves’ area and mark the hip rafter length – after
having worked this out from one of the methods previously covered. Square this mark across the top edge
and, from this point, mark a hip rafter plumb-cut D,
representing the external corner of the half-lapped wall
plate. If the hip rafters were receiving backing bevels
(dihedral bevels) on their top edges, plumb line D –
the important backing line reference for rafter-length –
would also be the line to measure down and mark the
same two-thirds measurement worked out for the
common rafter (as illustrated) to form the birdsmouth
after marking a hip rafter seat cut E at this depth.
12.13.3 Addition for Loss of Corner
Figure 12.33(c): Now, as the external corner of the
bedded wall-plate is usually removed, to allow a square
abutment of the hip plumb-cut against the wall plate,
it follows that the amount removed has to be added to
the hip plumb-cut in the birdsmouth. As illustrated,
the amount removed diagonally from the corner
geometrically equals half the thickness of the hip
Setting Out a Hip Rafter
153
BHRL
Hip
edge
∗
Wall
plate
D
Drop
∗ Corner-removal
∗
Slope
measurement
at eaves
2/3 C/R
F
E
equals half
thickness of hip
G
Figure 12.33 (c) Addition for loss of corner
rafter. Therefore, if the hip was 32 mm sawn thickness,
16 mm would be cut off the corner of the wall plate
and 16 mm would be added back into the birdsmouth,
as indicated by plumb line F in Figure 12.33(b).
12.13.4 Hip Rafters Without Backing
Bevels
Figure 12.33(d): This simplified hip rafter, left with a
square top-edge, is more in evidence nowadays, since
the economic omission of boarding (sarking) which
was fixed over the whole roof surface, under the sarking felt, some years ago. Therefore, having marked out
the top-end of the hip rafter, as described in the text
to Figure 12.33(a), hook in and run the tape rule
down to mark the length. As before, square this across
the top edge and from this point, mark a hip plumb
cut D, representing the external corner of the wall
plate. Next, the amount to be removed diagonally
from the wall-plate corner (half the thickness of the
hip rafter), say 16 mm, is measured into the body of
Hip
rafter
Figure 12.33 (d) Hip without backing bevels
the rafter, at right-angles to plumb line D, and
marked to become hip plumb cut E. This time, it is
this inner plumb line which, as illustrated, is marked
down with the same two-thirds measurement worked
out originally for the common rafter. At this depth, a
hip seat cut F is marked to form the birdsmouth.
12.13.5 Hip Rafter Eaves’ Projection
Figure 12.33(e): The total eaves’ projection for the common rafters, as described in the text to Figure 12.31(d),
was worked out to be – as an example – 355 mm from
the plumb cut backing-line to the plumb cut for the
fascia board, measured horizontally (or 433 mm measured down the slope of the rafter, as worked out by
the Roofing Ready Reckoner or the Roofmaster for a
35⬚ pitch). Using the common-rafter working out of
355 mm again for the hip-rafter eaves’ projection,
D
Angle-tie
position
Drop as
per C/R
H
Corner of wallplate removed
Hip
edge
cuts
G
Plan view
Fascia cuts can be marked
from jack rafter ends with
a straightedge
Figure 12.33 (e) Hip eaves’ detail
154
Constructing Traditional and Modern Roofs
bearing in mind that the hip is at 45⬚ in plan and is
therefore diagonally longer, you can find the horizontal
diagonal projection with the metric rafter square. Do
this by setting 355 mm on the blade and 355 mm
on the tongue and by measuring the diagonal, which, in
this example, produces a figure of 502 mm. A figure,
fractionally more accurate than this, can be found by
the other two methods; by using 45⬚ as the pitch and
the common-rafter-table figure per metre of run, i.e.
0.355 ⫻ 1.414 ⫽ 0.50197 m (say 502 mm)
12.13.6 Down the Hip-edge
Figures 12.33(d) and (e): Using the Ready Reckoner or
the Roofmaster to find an alternative measurement for
applying down the slope of the rafter, for the same 35⬚
pitch, the sum would be the run of the common-rafter
eaves’ projection, multiplied by the hip table-figure:
0.355 ⫻ 1.578 ⫽ 0.560 m (560 mm)
This would be applied from the top of the backing line
D to the top of another hip plumb cut to be marked at
G, from which hip edge cuts are marked, as illustrated,
against which the mitred fascia boards will be fixed.
12.13.7 Additional Notches
Figure 12.33(e): As illustrated, additional birdsmouth
notches might be necessary to clear wall projections
which clash with the hip’s extra depth. Alternatively, the
hip may be reduced in depth on the underside, from a
point starting from and equal to the bottom outer-edge
of the corner wall-plate, indicated by the dotted line H.
Also, if corner angle-ties are to be used, the notches for
them should now be marked ready for cutting on the
inner edges of the extended birdsmouth seat cuts.
∗
Hip
rafter
∗
∗ ⫽ Common rafter
12.13.9 Use for Marking or Checking
Where the hip rafter rests at the top, in a selfcentralizing position, the sides of the actual hip-edge
plumb cuts can be marked and where it rests at the
bottom, the actual plumb cut for the birdsmouth can
be marked. Then the seat cut for the birdsmouth can
be marked down (in the case of hips without backing
bevels) at two-thirds the common-rafter plumb-cut
depth. Alternatively, hip rafters that have already been
marked out by calculation can still be checked by this
technique, prior to being irreversibly cut.
12.13.10 Variation of Method
Figures 12.33(g) and (h): An interesting variation on the
above method is to omit the rafter offcut which equalled
two-thirds’ backing-line height, rest the length of hip
rafter on the actual diagonally offcut wall-plate edge
instead (Figure 12.33(h)), and again on the crown/
common rafter intersection at the top, mark these two
extreme resting points on the bottom-face of the rafter
Hip
rafter
Ridge
board
Saddle
board
backing-line height
Figure 12.33 (f)–(h)
Figures 12.33(f ) and (g): Finally, it must be mentioned
that the length of the hip and its eaves’ projection, rather
than relying completely on geometrical principles, is
often determined by practical methods, especially if the
walls at the hipped end are out of square or the wall
plates are out of level. One of many practical methods is
to reduce the width of a truly square-ended rafter offcut
to equal two-thirds the common-rafter backing-line
height (height above the birdsmouth), fix it temporarily
as illustrated in Figure 12.33(f ), to be flush to the diagonally offcut wall plate and rest a length of hip rafter on
it edgeways and on the crown/common rafter intersection at the top, as indicated in Figure 12.33(g).
Hip
rafter
∗
(f)
12.13.8 Practical Considerations
(g)
(h)
Setting Out Jack Rafters
and square them across the edge. This length of hip
material can now be used as a rod, to lay diagonally on
the face of a hip rafter previously set out by calculation,
to check that the rod-marks relate exactly to the marked
corner of the birdsmouth at one end while relating to
the top edge of the hip edge cuts at the other. Alternatively, hip rafters can be set out this way, without
length-calculation, by first marking out the eaves’ projection and birdsmouth and then by laying the rod to
run up diagonally from the birdsmouth corner, pivoting
as necessary at the top of the hip until the mark on the
rod relates to the top edge, where it is marked to become
the inner plumb cut of the hip edge cuts.
12.13.11 Eaves’ Drop
Figure 12.33(e): The practical way to deal with the hip
eaves’ projection, is to mark out and cut the soffit seat-cut
only, and leave the hip-edge plumb cuts for the fascia
board, to be marked and cut in situ by string-line or
straightedge, once the hips, commons and jack rafters are
fixed. The position of the hip rafter seat cut for the soffit
board is measured down vertically from the birdsmouth
seat cut, at a distance known as the drop. This drop measurement is taken from the pattern common rafter.
12.14 SETTING OUT JACK
RAFTERS
12.14.1 Calculated Diminish
As mentioned earlier in the text to Figure 12.11, jack
rafters, being equally spaced, should diminish in
length by a constant amount in relation to the length
of the common rafter. From information given in the
Roofing Ready Reckoner, the accompanying booklet to
the metric rafter square and the booklet that comes
with the Roofmaster, working out and applying the
diminish, to find the length of each pair of diminishing jack rafters, is not difficult to understand, but
again there is a practical method that can be used.
12.14.2 Practical Method
Figure 12.34(a): After the skeletal structure of a hipended roof has been pitched (the sequence yet to
come), the next operation is to fix the jack rafters in
pairs on each side of the hip rafters; start by working
away from one of the first pair of common rafters.
Ideally, you will need a steel roofing square, but an
improvised wooden square will do and can be quickly
and easily made out of, say 50 ⫻ 25 mm battens, to
resemble a miniature builder’s-square or, as illustrated,
155
to resemble a tee square, simply constructed with a
lapped, clench-nailed joint.
12.14.3 Technique
Figures 12.34(b) and (c): As illustrated, the tee square or
the roofing square is held firmly and squarely against the
common rafter, with the tongue resting on the hip-rafter
edge, while being slid up or down until the rafter-spacing
mark or measurement relates exactly to the inner edge of
the hip. At this point a mark is made and squared across
to the other edge on the crown-rafter side of the hip.
Edges A and B of this squaring, establish the highest
points of the positions of the first pair of jack rafters.
12.14.4 Centres of Rafters
Figure 12.34(d): Next, mark the spacing-distance of the
rafters (usually 400 mm centres on traditional roofs) on
top of the wall plate, away from the vertical face of the
common rafter. In practical terms, this will be 350 mm,
the distance between the common and the first jack
rafter. The spacing for the first jack rafters on either
side of the crown rafter, will be minus the thickness of
the saddle board, so the distance between these rafters
will be 350 ⫺ 18 ⫽ 332 mm. This dimension can also
be found by measuring squarely across from edge mark
B (Figure 12.34(c)) to the face-side of the crown, ready
to be reproduced on the wall plate. All following pairs
of jack rafters will conform to normal rafter spacing.
12.14.5 Marking the Length
Figure 12.34(e): Having gathered a selection of varied
offcuts and lengths of rafter material to be used up as
jacks, mark out and cut the birdsmouth on each (if not
the plumb cut for fascia) and lay aside. Next, take a
tape rule or, preferably, a measuring batten (rod), and
carefully check the distance by laying the rod in a
pitched position, from the edge of the wall plate E
(Figure 12.34(d)), up to the hip-edge mark A. Then,
mark these points onto the rod and transfer the rod to
the prepared jack rafter, to lay in a diagonal position,
relating to the corner of the birdsmouth E and being
marked at A, on the top edge of the jack rafter. From
this point, the jack edge cut and jack side cut are
marked, ready for cutting.
12.14.6 Fixing Pair After Pair
Figure 12.34(c): To avoid overloading one side of the
hip rafter, jacks should always be fixed in diminishing
pairs, exactly opposite each other. Once the first pair are
fixed, they can be used for relating to and continuing
the squaring technique for the next pair, as indicated at
C and D.
156
Constructing Traditional and Modern Roofs
Rafter
spacing
(a)
Ridge board
Common
rafter
Tee square
Saddle
board
Hip
First jack
rafter
A
B
C
Crown
rafter
D
(b)
(c)
Jack
edge
cut
B
Jack
side
cut
Length of
first jack
rafter
A
∗
∗ 350 mm
(d)
A
E
E
(e)
12.14.7 Setting Out Valley Rafters
Figure 12.35(a)–(c): Geometrically, a valley rafter is
identical to a hip rafter, but inverted. The plumb cut,
the seat cut and the calculated length are the same.
However, there are a few variations. First, because the
valley rafter usually stems from a ridge-board junction,
the reduction at the top from F to G, would be set in
squarely at half the diagonal thickness of the ridge board
(not the common rafter). Second, the plumb cut of the
birdsmouth can be shaped with hip-edge cuts to allow a
proper abutment against the internal angle of the wall
plate. This is shown here, marked out between plumb
lines H and I, equalling half the valley-rafter thickness,
measured out squarely. The third and final variation is
Figure 12.34 (a) Tee square;
(b) part-plan view. Marking position
of first pair of jack rafters; (c) part-plan
view. Marking position of second
pair of jack rafters; (d) centres of rafters
(e) marking the length
that when the feet of the cripple rafters are fixed, unlike
jack-edges on hips, their top edges should protrude
above the valley-rafter edge by the backing-bevel
depth, as indicated in Figure 12.35(c).
12.15 PITCHING DETAILS AND
SEQUENCE
12.15.1 Jointing the Wall Plates
Figure 12.36: Wall plates for gable-ended roofs are only
required on the two side walls from which the roof
Pitching Details and Sequence
157
H
Basic valley rafter
length (BVRL)
I
F
G
I H
2/3 C/R plumbcut height
(a)
(b)
CL
Figure 12.35 (a) Setting out of
valley rafters; (b) valley birdsmouth
wall plates would be required on all four sides. These
would be half-lap jointed on the four corners, as well as
where intermediate lengthening joints may be necessary. As illustrated, a sequence of lap-jointing should be
worked out to allow successive pieces of plate to be
dropped onto the open-joint and the mortar, rather
than be pushed under a wrong-sided lap joint – which
tends to trap the mortar in the under-joint.
12.15.2 Bedding the Wall Plates
Top edge of
cripple rafters
should line up
with centre of
valley rafter
Figure 12.35 (c) Protruding cripple edges
Bedding the wall plates is best done as a team effort
between carpenter and bricklayer. The bricklayer lays
and spreads the mortar, beds and levels the plates and,
in the case of a hip-ended roof, the carpenter checks
that they are square (by using the 3–4–5 method) and
parallel to each other across the span. To achieve this,
in the case of a gable-ended roof, slight lateral adjustments of the plates may be made – within reason. The
3–4–5 method referred to, is a practical application of
Pythagoras’ theorem of the square on the hypotenuse
of a right-angled triangle being equal to the sum of
the squares on the other two sides. When used for
squaring the wall plates, using metres as units, mark
3 m along the edge of one plate, 4 m along the edge of
the other and, to prove a true right-angle, the diagonal
measurement between these points should be 5 m.
12.15.3 Pitching a Gable Roof
Figure 12.36 Sequence of lap-jointing for wall plates
pitches. If the walls exceed standard timber lengths of
6.3 m, the wall plates would have to be joined in length
with half-lap joints, whereby the lap equals the width of
the timber. In the case of a double hip-ended roof, the
Figure 12.37 (a) Marking rafter positions on plate
and ridge
158
Constructing Traditional and Modern Roofs
Ridge
Scaffold
platform
Figure 12.37 (b) Inserting
ridge board
Figure 12.37(a): When the bedded plates are set, the
joints can then be fixed together with wire nails or
screws (screws being less likely to disturb the ‘green
mortar’). Then the ridge board may be laid out against
the wall plate, if possible, and the positions of the common rafters spaced out to the required centres (usually
400 mm) and marked across both members. Next, in
any of the clear areas indicated by the marking out, the
vertical restraint straps are fixed over the plates, close to
each end, one on each side of a lap-joint, and not more
than 2 m apart – and then the ceiling joists, with any
sprung edges kept uppermost, are fixed adjacent to the
rafter marks, either by skew-nailing with 75 or 100 mm
round-head wire nails or by being fixed into pre-fixed,
shoe-type metal framing anchors. The ceiling joists,
which are also fixed to the plates of any internal crosswalls, act as a working platform and should be close or
open-boarded with an area of scaffold boards.
12.15.4 Technique and Sequence
Figure 12.37(b): At each end of the roof, a pair of
rafters is pitched and fixed to the wall plates and the
ceiling joists, their plumb cuts supporting each other
at the apex. This is at least a two-man job, with one
man at the foot of each rafter. An interlocking scaffold can be erected through the ceiling-joist area and,
from this, the ridge board is pushed up between the
rafter plumb-cuts and fixed into position. Ideally, a
third man would do this. On each fixing, one 75 mm
round-head wire nail is driven through the top edge of
the rafter and two – one on each side – are skewnailed through the sides into the ridge board. The
nails first driven into the rafters’ top edges usually
pierce through the ridge board on each side, causing
problems unless both opposite rafter-heads are fixed
at the same time. To manage this single-handedly,
leave the first nail-head protruding until the nail on
the other side is partly or fully driven in.
12.15.5 Important Foot-fixings
The foot of each rafter must be fixed to the wall plate
and the ceiling joist (acting as a structural tie) with at
least three 100 mm round-head wire nails – one skewnailed above the birdsmouth into the plate, which, as
well as fixing, also tightens the rafter against the ceiling joist, and the other two driven in squarely through
the side of the ceiling joist, into the rafter, as previously indicated in Figure 12.7(a).
12.15.6 Adding Purlins and Struts
2⫻D
D
Scarf joint
Half-lap joint
Figure 12.37 (c) Purlin half-lap joint and scarf joint
2⫻D
Figure 12.37 (d) Ridgeboard scarf joint
Pitching a Hipped Roof (Double-Ended)
Figures 12.37(c) and (d): According to the length of
the roof (from gable to gable) and whether the purlins
or ridge board need to be extended in length by jointing – as illustrated – a few more pairs of rafters may
need to be fixed at strategic positions before the
purlins are offered up and fixed by skew-nailing from
above, through the available rafters, into the purlin
edges. The struts, set out by using a rod and/or riseand-run principle for lengths and bevels, are then
fixed into position. Next – to complete the main
structure of the roof – the remainder of the rafters are
filled in.
12.15.7 Restraint Straps
400
c/c
159
Saddle board
Clear
run
Run
Crown rafter
Clear run
Run
Figure 12.38 (a) Setting out a hipped end
Straps fixed to underside of rafters and noggings
Straps fixed to top of ceiling joists and noggings
Figure 12.37 (e) Restraint straps
Figure 12.37(e): Whether the gable walls are to be
built before or after the roof is pitched, it must be
remembered that horizontal restraint straps of 5 mm
thick galvanized steel must be fixed at maximum 2 m
centres across the ceiling joists and rafters, to be built
into (to help stabilize) the gable-end walls.
12.16 PITCHING A HIPPED
ROOF (DOUBLE-ENDED)
12.16.1 Setting out Wall Plates
Figure 12.38(a): After the wall plates have been halflapped (see Figure 12.36) and bedded into position,
they must be checked for being level, parallel and
square-ended. When the mortar has set and the joints
have been fixed, the rafter positions can be set out. This
will allow the vertical restraint straps to be fixed in any
of the clear areas – as described for the gable-roof wall
plates. To set out, check the actual span across the wall
plates and divide by two to find the run. Mark this as a
centre line on the wall plate at each hip-end and split
the thickness of the crown rafter on each side, to be
squared across the plates. The clear run is now measured and should equal the run minus half the crownrafter thickness. This measurement is now marked in
from each side of each hip-end and represents the face
of the saddle board. The thickness of the saddle board –
usually 18 mm WBP plywood or OSB – is now marked
across the plates and this line is equal to the face of the
first pair of common rafters at each end. The other
rafters are spaced out between these pairs, at specified
centres from one end, regardless of an odd spacing at
the other end.
12.16.2 Marking and Cutting
As mentioned earlier in this chapter, most – if not
all – of the marking and cutting of the various
components in the roof should be done on the
ground, laid out on pairs of saw stools, then hoisted or
man-handled up to the roof. Nowadays, the components may be cut with a compound-angled mitre saw.
12.16.3 Pitching Technique and
Sequence
First, the ceiling joists are fixed, but only those in the
middle area that attach to common rafters – not those
at each end that attach to jack rafters. As before, a
boarded area is laid with scaffold in position. The first
pair of rafters at each end are pitched and fixed. The
marked ridge board is inserted and fixed, the rafters
being braced diagonally down to the wall plates. Then,
the saddle boards are fixed at each end with 50–63 mm
round-head wire nails (at least six in each board),
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Constructing Traditional and Modern Roofs
followed by the crown rafters and then the hips – or
the hips and then the crown rafters, if using the alternative hip-arrangement illustrated in Figure 12.4(a).
12.17 FLAT ROOFS
12.17.1 Introduction
12.16.4 Adding Purlins and
Temporary Struts
After fixing a few more pairs of common rafters,
strategically placed to relate to any lengthening joints
in the purlins or ridge board, it will be found to be
advantageous to fix the purlins, after checking that the
hips are not bowed and, if necessary, bracing them
straight with diagonal battens down to the wall plates.
Fixing the purlins at this stage reduces the struggle
against a full complement of sagging rafters and provides an intermediate ledge upon which to manoeuvre
the rafters on their way up to the ridge. At this stage,
the purlins should be supported, if only with temporary struts until the joists at each end are complete and
the binders have been added.
The structure of flat roofs is very similar to that of
suspended timber floors, especially when kept level for
the provision of a ceiling on the underside. If the ceiling is unimportant, or not required, the joists may be
set up out of level to create the necessary fall (roof
slope). Like floors, the roof joists span across the
shortest distance between the load-bearing walls – or
the longest distance when intermediate cross-beams
are used – at similar centres to floor joists. They are
subject to the same rules as floors regarding strutting
being required when the span exceeds 2.5 m. Suitable
joist sizes can be obtained either by structural design
or by reference to Tables A17 to A22 for roof joists in
The Building Regulations’ Approved Document A, 1992
Edition.
12.16.5 Finishing Sequence
12.17.2 Anchoring
Roof
joist
Framing
anchor
Figure 12.38 (b) Return-joists on hipped end*
Restraint strap
over wall plate
(a)
Figure 12.38(b): Finally, cut and fix the jack rafters, the
remaining ceiling joists each end, the binders (skewnailed from alternate sides into the top of each ceiling
joist), the struts and straining pieces, the remaining
common rafters, the hangers and, if required, collars to
complete the main structure of the roof. On hipped
roofs, as illustrated, short return-joists are fixed to the
feet of the crown and jack rafters at the hipped ends.
These return-joists only provide fixing points for the
plasterboard ceiling at the wall-plate edge and, unlike
ceiling joists, do not act as structural ties. For this reason, the New Build Policy Guidance Notes BGN 9B, recommend that horizontal restraint straps or timber ties
(like binders) should be fixed across the tops of a minimum of three ceiling joists and be attached to the side
of the crown and every second jack rafter.
Side-fixing
restraint
strap
(b)
Figure 12.39 Flat roof details; (a) anchoring; (b) sidefixing restraint strap
Flat Roofs
Figure 12.39(a) and (b): As illustrated, the roof joists
are either fixed to the wall plates by skew-nailing with
round-head wire nails or by framing anchors.
Galvanized restraint straps are fixed over the plates
and to the inside face of the wall, as described for
pitched roofs, at maximum 2.0 m centres – or, without
wall plates, the joists may be anchored to the top of
the walls with twisted side-fixing restraint straps.
12.17.3 Creating a Fall
Roof joist
Wedge-shaped firring piece on joist running with the fall
Diminishing firring-pieces on joists running accross the fall
(c)
Figure 12.39 (c) Firrings
Figure 12.39(c): Wedge-shaped timber fillets, or diminishing parallel-fillets, known as firring pieces, are fixed
to the upper joist edges to create the necessary fall or
roof slope. The recommendations for these falls vary
between as low as 1 in 80 (25 mm in 2.0 m) and 1 in 40
(25 mm in 1.0 m). The New Build Policy Guidance Notes
BGN 9A recommend the latter as a minimum fall for
flat roofs. An alternative method of creating a fall,
available nowadays, is to keep the structural roof truly
flat and create the fall above the roof deck by using a
system of pre-designed tapered roof insulation boards.
12.17.4 Flat Roofs Against Buildings
Cavity tray
Flashing
50 ⫻ 50 mm
angle fillet
Built-up roofing felt (stone
chippings not indicated)
75 mm mineral-faced apron
on 50 ⫻ 25 mm drip fillet
Wall plate
Vapour barrier
Sheet decking
Rigid insulation
Firring piece
Preservative-treated joists
75 ⫻ 50 mm continuous edge-nogging
Figure 12.40 (a) Flat roof butted to adjacent walls
Figure 12.40(a): Flat roofs may be independent (as on a
detached garage, Figure 12.40(c)), or have one or more
161
edges butted up to the face of an adjacent building.
Sometimes, on single-storey buildings such as bungalows, the abutment is weathered-in with the pitch of
the main roof at eaves’ level. In the case of abutments to
walls, the roofing material is turned up the wall and is
covered by a lead flashing chased into the wall at a minimum height of 150 mm above the roof.
12.17.5 Cavity Trays
If the wall is of cavity construction, a cavity tray must
be built in or be inserted to lap onto the top edge of
the flashing, as illustrated in Figure 12.40(a).
However, this creates a problem in conversion work,
where a lean-to or flat roof is butted-up to a wall as an
afterthought, and involves the bricklayer in cutting
away a brick-course of the existing wall in a piecemeal
operation to allow for building in a cavity-tray system.
12.17.6 Joists Into or Against a Wall
Figure 12.40(a) shows the joists at right angles to the
adjacent wall, built into the outer skin of brickwork.
They may also be carried on galvanized, type TW
(timber to wall) joist hangers – a popular method in
conversion work, as the top flange of the hanger is
easily cut into a mortar-bed joint in the brickwork.
This can be done with a disc angle-grinder and/or a
traditional plugging chisel. When the hangers are
inserted, any gaps above the flange should be caulked
with bits of slate or strips of sheet lead.
12.17.7 Roof Fabric
The most common covering to flat roofs for some
years now, has been bituminous roofing felt, although
it has a limited life-span up against more traditional
coverings such as mastic asphalt, sheet lead or copper.
However, high-performance roofing felts are now
available, built-up as before in three layers and highperformance GRP (glass-reinforced plastic) flat roofs
are also being marketed with a 25-year guarantee.
12.17.8 Decking Material
Sheet decking is laid and fitted on the roof joists, firrings or counter-battens, with cross-joints staggered
in a similar way to flooring panels, fixed down with
50–56 mm by 10 gauge annular-ring shank nails at recommended 100 mm centres. Types of decking material
include WBP exterior grade plywood, Sterling OSB
board, moisture-resistant or bitumen-coated chipboard
and pre-felted chipboard with roofing felt bonded onto
the top surface.
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Constructing Traditional and Modern Roofs
12.17.9 Board Thicknesses
Thickness of decking is related to the joist-spacing –
plywood can be 12 or 15 mm for joists at 400 mm
centres, Sterling board 15 mm and chipboard 18 mm.
When joists are at 600 mm centres, the thickness
should increase to 18 mm for plywood, 18 mm for
Sterling board and 22 mm for chipboard. Nails should
be at least 21-2 times the thickness of the board, so only
the 22 mm chipboard qualifies for the 56 mm nails
mentioned above. Decking should be laid with a 3 mm
expansion joint between boards and board-joints
should be covered with 100 mm wide bitumen felt
strip to protect the edges of the boards while awaiting
the arrival of the roofing specialist.
50 ⫻ 50 mm counter-battens for ventilation
Short return-joists, firred on top edges, with edgenoggings between 50 ⫻ 50 mm angle fillet
Vapour barrier in the form
of foil-backed plasterboard
Ventilation each side
equivalent to a continuous
25 mm gap
Mineral-faced apron formed
over 18 mm resin-bonded
plywood fascia
Figure 12.40 (b) Verge details
12.17.10 Projecting Eaves and
Verges
fascia-fixings and for better continuity of the whole
roof structure.
Figures 12.40(b) and (c): When projecting eaves
and/or verges are required for design purposes or to
allow for ventilated soffits (as is necessary for cold
roofs), the joists can be extended in length across the
wall and made to extend on the sides. As illustrated
three-dimensionally in Figure 12.40(c), this is
achieved by the formation of short, projecting returnjoists fixed at right-angles to the sides of the outer
joists by using type TT (timber to timber) joist hangers,
framing anchors or simply by skew-nailing. Even
if the fascia boards are to be kept close to the face
brickwork, these short return-joists will be needed for
12.17.11 Insulation to Flat Roofs
The Building Regulations’ Approved Document F2 states
that excessive condensation in roof voids over insulated
ceilings must be prevented, otherwise the thermal insulation will be affected and there will be an increased risk
of fungal attack to the roof structure. This applies only
to roofs where the insulation material is at ceiling level
(cold roofs). Where the insulation is kept out of the
roof void, placed on the deck (warm roofs), the risks of
excessive condensation developing are not present and
these roofs, therefore, are not covered.
Note
Fascia boards on side-verges
may be tapered or parallel,
depending on joists being
levelled and firred or
sloping in themselves
Fall
Figure 12.40 (c) Partlyexposed view of
independent flat roof
(Note: Counter-battens for
ventilation – as shown in
Figure 12.40 (b) – omitted
here.)
Flat Roofs
12.17.12 Categories of Flat-roof
Construction
There are three to be mentioned. The first, which is
preferred nowadays because a better balance between
heat-loss and condensation-control can be achieved, is
known as a warm deck flat roof, which does not require
ventilation of the roof void. The second, which does
require ventilation and is more susceptible to condensation, is known as a cold deck flat roof. This type of
roof, although covered by The Building Regulations of
England and Wales, is not recommended in The
Building Standards Regulations of Scotland (in which
warm roof constructions are recommended). The third
category of roof is known as a hybrid flat roof, covering
certain roofs which do not fall within the warm or cold
category. This is because some structural decks are
themselves composed of insulating materials, such as
woodwool or, in other cases, insulation is added above
the deck in addition to insulation at ceiling level.
12.17.13 Warm Deck Flat Roof
Figure 12.40(d): The main feature of this roof is that
the insulation is placed above the structural deck in
the form of rigid boards, such as Thermazone polyurethane foam roofboards. These particular boards are
600 ⫻ 1200 ⫻ 50 or 80 mm thick; their edges are
rebated for interlocking to avoid cold bridging and
they have bitumen glass fibre facings on each side.
Three-layer felt roof with
stone chippings
Do not ventilate
roof void
Preservative-treated
joists
Firring pieces
Decking
Vapour barrier
Rigid insulation
Wall
insulation
carried on
up to roof
insulation
Figure 12.40 (d) Warm deck flat roof (eaves’ detail)
12.17.14 Construction
Figure 12.40(d): The rigid insulation is bonded or fixed
with mechanical fastenings to a layer of felt vapour
barrier, which has been fully bonded to a sheet decking. The decking is fixed to tapered firring pieces
which are fixed to the joists. To avoid cold bridging
around the perimeter of the roof, any cavity insulation,
163
as illustrated, should be carried on up to meet the deck
insulation. In this type of construction, the roof-void is
not to be ventilated. All roof timbers should be preservative-treated. The waterproof covering to the roof is
recommended to be of three-layer high performance
built-up felt or GRP.
12.17.15 Cold Deck Flat Roof
50 mm minimum airspace
for ventilation
Fascia
board
Vapour barrier
Insulation
Preservative-treated
joists
Firring pieces
50 ⫻ 50 mm counter-battens
Decking
Soffit vent
to be
equivalent
to a 25 mm
continuous
gap
Figure 12.40 (e) Cold deck flat roof (verge detail)
Figure 12.40(e): The main feature of this roof is that
the insulation is placed below the structural deck,
between the joists at ceiling level. To avoid cold bridging, the ceiling insulation should join up to the cavity
insulation, as illustrated, with care being taken not to
block the perimeter air vents. These vents, positioned
in the soffit area, can be continuous or intermittent
and must be on opposite sides of the roof for crossventilation. Where this is not possible, then this type
of roof should not be used. The opening of the vents,
incorporating an insect screen mesh, should be equivalent to a continuous 25 mm gap. Additional, intermediate roof vents are recommended for spans over
5 m and for roofs with an irregular plan-shape.
12.17.15 Construction
Figure 12.40(e): Approved Document F2 also recommends that there should be a free airspace of at least
50 mm between the insulation and the underside of the
roof deck. This will not normally cause a problem if
the continuous air vents can be placed at right-angles to
the joists on opposite sides of the roof, but in situations
where the air vents are parallel to the joists, as illustrated, airflow across the joists can be achieved by positioning 50 ⫻ 50 mm counter-battens at joist-spacings
across the roof joists, fixed on top of the firring pieces
164
Constructing Traditional and Modern Roofs
externally with ex. 25 mm diagonal boarding (parallel
to the roof slope) or 15 mm WBP plywood or Sterling
OSB board. If the cheeks are to receive tile or slate
cladding, a breather membrane, such as Tyvec Supro
(not a roof underlay), should be fixed to the sheathing
behind the preservative-treated tile battens. The windows can be uPVC from the outset, but are usually
specified initially (for economy) to be the wooden
stormproof casement type, with wide rebates for
14 mm double-glazed sealed units.
and to the short, projecting return-joists. Under the
insulation (which can be of a rigid or flexible, but not
loose type), a vapour barrier should be placed at ceiling
level, using minimum 500 g polythene or metallized
polyester-backed plasterboard. All roof timbers, as
before, should be preservative-treated and the waterproof roof-covering should be as recommended for the
warm deck flat roof.
12.18 DORMER WINDOWS
AND SKYLIGHTS
12.18.2 Dormer Roof
Figure 12.41: The roof may be flat and the
100 ⫻ 50 mm minimum joists firred to slope backwards to the main roof or to fall to a front gutter and
corner down-pipe which discharges onto the main
roof. Dormer roofs may also be segmental, semi-circular, etc., or pitched with a gable end or hipped end and
tiled or slated in keeping with the main roof. Typical
construction details of the skeletal dormer are shown
in the illustration. All timbers not rated according to
BS 5268: Part 5, should be preservative-treated and
the waterproof roof-covering should be as recommended for the warm-deck and cold-deck flat roofs.
12.18.1 Introduction
Roof lights in the form of dormer windows and skylights are usually found in roof spaces used for storage
or habitation. Both of these windows involve a trimmed
opening in the roof slope and the use of thicker trimming and trimmer rafters, according to the size of
opening and the amount of trimmed rafters to be carried. The trimming rafters that carry the trimmers and
their load of trimmed rafters, can also be – and usually
are nowadays – formed by fixing two common rafters
together, as indicated in the illustration.
12.18.3 Ventilation and
Condensation Control
12.18.2 Dormer Windows
Figure 12.41: These traditional constructions protrude
vertically from the eaves or middle area of the roof
and have triangular sides known as cheeks, framed up
from minimum 100 ⫻ 50 mm sawn studs, sheathed
Vertical
trimmer
Figure 12.42(a): Where there is a well-ventilated space
within a pitched roof, above the insulation at ceiling
level, a vapour control layer is not normally required;
100 ⫻ 50 mm joists
Short returnjoists each side
Double
trimming
rafters
Double
head-plate
beam over
window
100 ⫻ 50 mm
head plate and
studs
Built-up
corner post
50 ⫻ 50 mm
edge-fillets
Double trimming
rafters
Trimmed rafters
Vertical trimmer
Figure 12.41 Skeleton dormer with
window omitted
Dormer Windows and Skylights
Figure 12.42 (a) Ventilation and continuous insulation
165
Figure 12.42 (b) Maintaining minimum 50 mm airspace
by using push-fit baffle boards
but where there is limited space above the insulation,
making it difficult to ventilate effectively, as in the
case of a loft room (attic), a vapour control layer would
be necessary, as and where indicated in the illustration. The whole loft area, including the dormer,
should be insulated up against the dwelling-side of the
construction, against the vapour barrier, between the
timbers of the dormer cheeks, the joisted roof, the
rafters where affected, the ceiling joists, the limited
areas of floor joists behind the ashlaring and between
the ashlar studs as well.
12.18.3 Detailed Recommendations
Figure 12.42(a): In recommending the above, BS 5250
also recommends that the insulation on inclined and
vertical faces must be held firmly in place to prevent
slipping and that where there is limited space for the
insulation, such as above the ceiling to the sloping
rafters, a minimum 50 mm clear airspace between the
insulation and the sarking should be provided. To
achieve this, it may be necessary to increase the size of
the roof and dormer timbers to accommodate the correct thickness of insulation.
12.18.4 Ventilation Requirement
Figures 12.42(a)–(c): To ensure the 50 mm clear airspace
is maintained, BS 5250 suggests that consideration be
given to installing some form of inert baffle boarding
between the roof timbers to restrict the insulation. This
recommendation could be met by using strips of 12 mm
thick soft-fibre insulation board, easily cut on site, or
pre-cut by the supplier’s mill from the imperial-sized,
metricated boards of 2.440 ⫻ 1.220 m. The strips could
be cut slightly oversize and pushed into a friction fit
and/or positioned against small protruding pre-set
nails, as indicated in Figure 12.42(b). A separate baffle
board, about 200/250 mm wide, is recommended
between each rafter at the eaves, above the structural
Figure 12.42 (c) Maintaining minimum 25 mm airspace
by using baffle boards*
wall, again to restrict the insulation and so ensure that a
minimum 25 mm clear airspace is maintained at this
point, as indicated in Figure 12.42(c).
12.18.5 Low-Level and High-Level
Ventilation
Figures 12.42(a) and (c): With roofs pitched above 15⬚,
low-level eaves’ ventilation should normally be equivalent to a continuous 10 mm gap, but where there are
areas of limited space above the insulation, as with
an attic or loft room, the opening area of the vents –
incorporating an insect screen mesh – should be
increased to be equivalent to a continuous 25 mm gap,
as indicated in Figure 12.42(c), and high-level
166
Constructing Traditional and Modern Roofs
ventilation openings at the ridge should be provided,
equivalent to a continuous 5 mm gap.
12.18.6 Mid-roof Ventilation
Figure 12.42(a): Additional ventilation openings
should be provided when there are obstructions in the
ventilation path, such as a roof light or dormer window. These vents should be placed immediately below
the obstruction, equivalent to 5 mm ⫻ obstructionlength and immediately above the obstruction, equivalent to 10 mm ⫻ obstruction-length. Finally, to
achieve cross-ventilation within the dormer’s colddeck flat roof, counter-battens, as described earlier,
will have to be used.
12.18.7 New Regulation
Requirements
Regarding the details shown in the roof section at
Figure 12.42(c), the insulation would now need to be
upgraded to comply with the new regulations. By
using the Elemental Method of achieving tabled
U-values in the thermal elements – only allowed in
ADL1B and ADL2B – the insulation would need to
be increased, as shown in Figure 12.42(d). This could
be in the form of mineral wool quilt, such as Crown
Wool, of 100 mm thickness laid between the ceiling
joists, with an additional 150 mm thickness laid over
the ceiling joists. To avoid cold-bridging, partial-fill or
full-fill insulation in the cavity walls should continue
up to connect with the roof insulation.
Polyethylene
breather-type membrane
Black PVC eaves carrier
Naturally-vented
batten space
Traditional felt underlay
Vapour
control
membrane
Vapour
control
membrane
Non-vented
soffit
Figure 12.42 (e) Non-ventilated ‘cold roof’ with breather
membrane, 250 mm ceiling-insulation and full cavity-fill
Eaves ventilation
Figure 12.42 (d) Ventilated ‘cold roof’ with roofing felt
underlay, 250 mm ceiling-insulation and wider baffle-board
Figure 12.42(d): As outlined in chapter 8, under section 8.2.2, regarding floors, radical changes have been
made to the regulations concerning the Conservation
of fuel and power. These initially came into force in
April 2002 as Approved Documents (AD) L1 and L2
and have now been amended and expanded into four
separate documents known as ADL1A, ADL1B,
ADL2A and ADL2B. These came into force in April
2006 and are accessible on line via www.odpm.gov.uk.
Figure 12.42(e): Research in recent years has established that condensation in roof voids (lofts), that
came about with the introduction of loft-insulation
three or four decades ago, is caused through there
being an impermeable membrane over the rafters in
the form of traditional roofing felt under the tilebattens. Although proper ventilation eliminates this
problem, it also adds to heat-loss. It was only when a
breather-type membrane – such as Tyvec Supro – was
introduced to replace roofing-felt, that roof ventilation
became unnecessary. Any moisture vapour trapped in
the roof void escapes through the breathable membrane into the tile-batten space.
As illustrated in Figure 12.42(e), Tyvec® rigid PVC
Eaves Carriers are laid over the edge of the fascia
Dormer Windows and Skylights
board and are fixed to the splayed tilting fillet with
large-headed galvanized clout nails, of 20 or 30 mm
length. The carriers, which are 1.3 m long, must overlap each other by 100 mm when joined end-to-end.
Tyvec® double-sided butyl tape is then applied to the
Eaves Carrier rebate. The breather membrane is
draped horizontally over the rafters, so as to form a
minimal 10 mm drainage-sag (maximum 15 mm)
under the tile battens, and fixed with non-ferrous
staples or nails at maximum 300 mm centres. The
membrane is lapped onto the carrier by 150 mm and is
finally bonded to this by peeling off the backing paper
from the previously bonded Tyvec® Butyl Tape.
Subsequent layers of breather membrane are fixed
progressively up the roof, each with a 150 mm overlap.
Note that because the breather membrane ‘drapes’
slightly in this example of a non-ventilated ‘cold roof ’,
it is referred to by Dupont™ Tyvec® as being of
‘unsupported application’ and the membrane that they
recommend for this is Tyvec® Supro.
To upgrade this roof further, a Tyvec® Supro Plus
membrane could be used. This has the advantage of
having an integral adhesive lap tape on its top edge,
allowing all horizontal edges to be bonded to produce
a more thermally efficient sealed roof system.
However, to achieve this, the breather membrane is
not draped and needs to be fixed to the rafters in a
taut condition with 25 ⫻ 50 mm counter-battens
fixed over. These should be fixed with 65 ⫻ 3.35 mm
Breather membrane
38 ⫻ 50 mm counter-battens
fixed with Inskew 600 fixings
Insect guard
fixed over
double-crossed
tile battens
Tyvec® SD2 or
polythene vapour
control membrane
taken up into
loft room
Non-vented
soffit
Tyvec® PVC eaves carrier fixed to tilting fillet
Figure 12.42 (f) Non-ventilated ‘warm roof’ with counterbattens, breather membrane and rigid insulation between
and over rafters
167
galvanized or sherardized round headed wire nails,
ready for tile-battening and tiling to complete.
Figure 12.42( f ): This detail of a loft room (to be
compared with Figure 12.42(a), which shows a loft
room in a ventilated ‘cold roof ’), is an example of a
non-ventilated ‘warm roof ’ construction, achieving
higher thermal efficiency. Because the breather
membrane is close to the rigid insulation fixed over the
rafters, it is referred to as being of ‘supported application’. For this, Dupont™ Tyvec® recommend the use
of either of their above named membranes or a third
membrane known as Tyvec® Solid, which is of lighter
weight. The sealing of horizontal lapped edges on this
membrane is optional, but, if required to achieve a
sealed roof system, it is easily done from above with
Tyvec® single-sided tape.
The two layers of rigid insulation shown here could
be 48 mm Celotex GA2000. One layer is laid over the
rafters, ready for fixing – which is done through the
counter-battens – and the other is fitted friction-tight
between the rafters (usually fitted later from inside the
loft space). As illustrated, a timber stop-batten, equal to
the insulation thickness, is fixed behind the fascia board.
This has two purposes; 1) It stops any downwards slide
of the roof-loaded insulation, 2) It gives upper support
and a fixing for the fascia board and tilting fillet.
The fixing of the counter-battens is a critical operation, because special stainless steel nails – known as
Inskew 600 (600 meaning 6.00 mm Ø) fixings – are
used, and they have the important task of holding the
counter-battens and the rigid insulation to the rafters.
These fixings, from Helifix Ltd, are also known as helical warm roof batten fixings. They are headless and, as
the name suggests, have a spiral shape. Sizes range
from 75 mm to 150 mm in 5 mm increments and from
150 mm to 250 mm in 10 mm increments. Fixings up
to 125 mm can be driven in by hammer-only, but
longer fixings need the assistance of a PDA (power
driver attachment) or a so-called Hand Supportal tool.
The length of a fixing is determined by the thickness
of counter-batten, plus the insulation, plus a minimum
35 mm into the rafter. As minimal 38 ⫻ 50 mm
counter-battens are recommended in the example roof
shown in Figure 12.42(f ), Inskew 600 fixings would
need to be not less than 38 ⫹ 48 ⫹ 35 ⫽ 121 mm
long. The nearest available size, therefore, would be
125 mm. Helifix Ltd recommend that the spacing of
fixings has to be calculated according to varying criteria, but should not be less than 150 mm, nor more
than 400 mm centres. Finally, because it would not be
practical – or safe – to fit and lay the rigid insulation
over the whole of the roof in an unfixed state,
awaiting fixings through the counter-battens, the
insulation is laid in manageable amounts and short
lengths of counter-batten are fixed progressively to
hold it.
168
Constructing Traditional and Modern Roofs
12.19 SKYLIGHTS (ROOF
WINDOWS)
12.19.1 Introduction
These lay in the same plane as the roof slope and traditionally consisted of a glazed skylight window, hinged
on the underside at the top and fixed to a raised curb
or lining. Although metal aprons of lead, zinc, etc.
were fixed to the back and side edges of the skylight,
these windows were not always weathertight.
12.19.2 Roof Windows
fixed across the ceiling joists and similar-sized struts
are fitted between the high and low plates. If possible,
the struts should be at right-angles to the roof slope.
The affected rafters can now be cut and removed
safely to enable a top and bottom trimmer to be fixed
in position. The faces of trimmers should also be at
right-angles to the roof slope. When the trimmers are
fixed to the trimming rafters and to the ends of the
newly trimmed rafters, the shoring can be released.
12.20 EYEBROW WINDOWS
12.20.1 Introduction
Figure 12.44 (a) Eyebrow window
Figure 12.43 Roof window (skylight)
Figure 12.43: Modern skylights, referred to as roof windows by the manufacturers, are a different proposition.
These skylights are very sophisticated and reliable.
They are made from preservative-impregnated
Swedish pine, clad on the exterior with aluminium.
The casements are of the horizontal pivot type with
patent espagnolette locks, seals and draught excluders,
and are double glazed with sealed units. The windows,
suitable for roof pitches between 20⬚ and 85⬚, are easily fixed to the rafters with metal L-shaped ties provided. Metal flashings and full fitting and fixing
instructions are also supplied with each unit.
12.19.3 Loft Conversions
If these windows are to be installed in a roof already
tiled or slated, as in a loft conversion, depending on
the size of the window, it may be necessary to shore
up the roof temporarily within the loft, to enable the
opening to be made. This can be as simple as fixing
two 100 ⫻ 50 mm timber plates, flat-faced across the
rafters, one slightly higher than the proposed opening,
the other slightly lower; 100 ⫻ 50 mm sole plates are
Figure 12.44(a): The eyebrow window is another form
of roof light, serving roof spaces used for storage or
habitation. This type of window is similar in most
respects to a dormer window, whereby a trimmed opening in the roof slope will be required with triangular
studded cheeks to the sides of the opening. These
cheeks, which emanate from the trimming rafters, are
not seen externally – unlike the cheeks of a dormer,
which are seen. Vertical timbers known as ashlar studs
are fixed to the underside of the window trimmer, the
top edge of which should protrude about 100 mm above
the roof slope to form the apron below the window sill.
As with the dormer, the window, in a present-day construction, would initially be of the wooden stormproof
casement type. To keep the window independent, to
allow for future replacement, the old practice of resting
the ceiling joists on the head of the window frame
should be avoided. Instead, they should span from the
upper trimmer in the roof to the double-plated beam at
the head of the structural window opening.
12.20.2 Eyebrows and Steep Pitches
Figure 12.44(b): Roofs with tiled eyebrow windows
need to be of a steep pitch of about 50–60⬚ to accommodate the shallower pitch of the curved roof to the
raised eyebrow, which should not be less than 35⬚.
This is because the only tiles that can be used on roofs
with eyebrows are non-interlocking 165 mm ⫻
265 mm (6 -12 in ⫻ 10-12 in) plain tiles, which are not
Eyebrow Windows
C
D
Q
B
B
2
K
I
F
J
J
I
H
CL
M
K
M
B
E
169
X
Normal to curves
E
F
A
Figure 12.44 (b) Setting out the eyebrow shape
recommended for roofs below 35⬚ pitch. As illustrated, the geometry for the serpentine shape of the
eyebrow is best established to suit the predetermined
window height and width.
12.20.3 Setting out the Eyebrow
Shape
Figure 12.44(b): First, in scaled form (usually done by
the architect), draw the outline of the window frame
with a centre line A–B drawn vertically through it. By
trial and error, try the compass or trammel point at different positions on the centre line until a suitable segment appears to fit above the frame. Now determine
the outer limits of the segment by judging a suitable
point E, near the base of the window frame and draw
a line through it, radiating from the centre A. Measure
the straight distance between E and B and set the same
distance from B to mark point F. Establish another line
radiating from centre A through F. These lines are geometrical normals to the curves required in reverse positions (cyma reversa) and at judged points along these
normals, as at C and D, the centres can be established
to complete the eyebrow (serpentine) shape.
12.20.4 Method of Construction
Figure 12.44(c): The construction details of traditional
eyebrow windows can be found to vary to some extent,
thereby creating variations in the methods of construction that are used. However, the following method is
recommended. Assuming that the skeletal structure of
the main roof is nearing completion and a free space
between the double trimming rafters is already established to accommodate the eyebrow window, the first
step is to position and fix the 100 ⫻ 50 mm floor plate
A to the floor joists, ready to carry the ashlaring. Then,
against the inside face of the double trimming rafters, fix
a vertical stud B on each side of the opening, extended
in height to run up about 50 mm above the estimated
roof curve. Now fix the trimmer C between the vertical
studs B, by forming housing joints, nailing or with modern fasteners such as Mafco CL-type framing anchors.
X
E
F
C
1
Q
G
Vertical
section
D
A
C
G
Double
trimming
rafters
Part elevation
O
1
H
50 ⫻ 50 mm
corner post
B
E
Section X–X
Figure 12.44 (c) Method of construction
12.20.5 Sub-sill/Apron to Window
Next, cut and fix the ashlaring D to the floor plate and
trimmer, at centres equal to rafter-spacings. Then cut
and fix the sub-sill E between the vertical studs B,
with the top edge protruding at least 100 mm above
the roof to act as an apron below the window; the subsill is also fixed to 100 ⫻ 50 mm offcuts F, pre-fixed to
the trimmer. Now complete the bottom section by
cutting and fixing the trimmed rafters G to the wall
plate at the bottom and the trimmer C at the top.
Above the sub-sill now cut and fix the vertical subframe stud H to the face of stud B on each side of the
opening, equal in height to the window frame plus a
minimum tolerance of 7 mm for fitting and for the
lead apron to be dressed under the sill. Studs H act as
bearings for the double head-plate beam I over the
window, which should now be cut to length, fixed
together by stagger-nailing through the face side at
about 400 mm centres, then fixed in position at each
end with 100 mm round-head wire nails.
12.20.6 Upper Trimmer and Trimmed
Rafters
Now start the ceiling structure by levelling across from
the top of the head-plate beam I and marking the side
of the trimming rafters on each side of the opening.
170
Constructing Traditional and Modern Roofs
This establishes the underside of the upper trimmer J,
which should now be cut and fixed in a similar way to
that described for the lower trimmer. Next, with
birdsmouth cuts at the foot and plumb cuts at the
head, cut and fix the trimmed rafters K from trimmer
J to the ridge board.
12.20.7 Ceiling above the Window
The 100 ⫻ 50 mm ceiling joists M can now be fitted
and fixed. They rest on the window-head beam I and
are skew-nailed flush to its front edge, while at the
other end they are fixed to the face of the trimmer J in
various ways similar to fixing the ends of the trimmers
C and J. As illustrated in the elevational view in
Figure 12.44(c), the ceiling joists M should be positioned and fixed immediately to the side of an alignment with the trimmed rafters K.
with 100 mm wire nails. Next, notch the head-plate N,
in a similar way to O1, to fit against the trimming rafter
near trimmer J and cut to length to fit squarely on top
of stud O1 and fix in position. Now, at 400 mm centres,
fit and fix the remaining vertical studs O2, O3 etc., similar to O1, fixed at the head and through the half-lap
notch. Finally, cut and fix the 50 ⫻ 50 mm edge fillets
P as shown.
12.20.10 Making the Full-size
Template/Sheathing
Rafter-cutouts
Board-joint
Figure 12.44 (e) Making the template/sheathing
12.20.8 Studded Side Cheeks
M
N
3
N
O
2
O
1
O
R
P
Outline of
extended
side
cheeks
P
O
R
Pictorial view
Figure 12.44 (d) Studded side-cheeks
Figure 12.44(d): Sometimes the side cheeks of dormer
and eyebrow windows – or a part of them, as illustrated by the broken lines – are carried on down to the
floor and the line of ashlaring each side of the window
takes up more of the available floor space, giving an
increased vertical face to the dwarf walls of the room.
However, the following notes assume that the cheeks
are to be triangular.
12.20.9 Triangular Cheeks
First, notch the bottom of stud O1, as seen at R in the
pictorial illustration, to lap onto the trimming rafter,
then cut squarely to length to finish 50 mm below the
top of the window-head beam. Fix to the side of stud B
and through the half-lap notch to the trimming rafter
Figure 12.44(e): The next important step is to lay out one
or two sheets of 12–18 mm WBP plywood or Sterling
board and by scaling measurements from the working
drawing, set out the eyebrow shape full size by using the
geometrical method already described. The idea is that
these boards should be set out to include the whole vertical face of the eyebrow window. This will give the dual
advantage of the board(s) being fixed against the front
of the studded structure already erected, to act as a template for the formation of the eyebrow shape, while also
becoming a permanent sheathing.
12.20.11 Marking the Rafter Cutouts
Once the eyebrow shape is marked, it should be cut
out with a jigsaw. Next, the eyebrow-rafter positions –
equal to the main roof common-rafter centres – must
be marked around the curved edge of the template and
set down for depth, as indicated in Figure 12.44(e), giving the appearance of a castellated edge. To simplify
this, the one- or two-piece template can be laid out flat
on the roof slope, either immediately below the window
opening, with the template’s base resting against temporary nails driven in near the fascia plumb-cut, as
indicated at Q1 (Figure 12.44(c)), or on the roof slope
above the window, with the base resting against the
ceiling joists M, as indicated at Q2. Either way, the
template must be in an exact position laterally, i.e. the
centre of the template must be equal to the centre of
the window-width. Resting against the rafters like this,
their positions can be easily marked onto the curvedtemplate edge and lines drawn down at right-angles to
the base, equal in depth to the eyebrow-rafter plumb
cut, as illustrated in Figure 12.44(f ).
Eyebrow Windows 171
35⬚, around the serpentine profile, the surface shape
and its effect on the eaves is geometrically similar to a
cylinder resting at 35⬚ to the horizontal plane, whereby
its base, representing the eaves, would be at 55⬚ to the
horizontal plane. From a side elevation, this would be at
right angles (35⬚ ⫹ 55⬚ ⫽ 90⬚) to the cylinder/roof
slope, as indicated between points A, B and C in the
illustration. This can be proved in a practical way by
bending a strip of 6 mm plywood, say 265 mm wide,
equal to the tile depth, over the eyebrow shape near the
edge and noting that it would follow the same path
indicated at A–B. If you can imagine this plywood strip
being equal to a line of tiles laid side by side, you should
then appreciate that the unequal projection of the eaves’
edge must be like this for the tiles.
35°
∗
∗
Part side-elevation
of eyebrow rafter
Part frontelevation
of template
Figure 12.44 (f) Cutouts equal plumb-cut depth*
12.20.12 Cutting the Window
Opening
12.20.14 Fixing the Template
Before removing the template/sheathing from the roof to
make the cutouts, it should be offered up and adjusted
for its true position against the face of the studded structure, then marked around the inside edge to outline the
window opening. This, then, can be cut when making
the cutouts for the eyebrow rafters – which should now
be done, again with the aid of a jigsaw.
The template/sheathing board(s) should now be fixed
lightly in position, to be stable enough to work against,
but able to be removed easily if necessary. This is
because the studwork yet to be built-up behind the
template might be awkward to fix properly in certain
places with the template in position.
12.20.13 Pitching the Eyebrow Roof
12.20.15 Eyebrow Rafters
Figure 12.44(g): It must be appreciated that, because
the eyebrow rafters are pitched at the same angle, say
The eyebrow rafters, seen in their diminishing lengths
in Figure 12.44(g), have an acute-angled cut at one end
C
C
B
B
A
1
A
Side elevation
A
3
Front elevation
Figure 12.44 (g) Formation of eyebrow rafters: left, side elevation; right, front elevation
A
2
172
Constructing Traditional and Modern Roofs
for fixing to the top edges of the main roof ’s rafters, like
sprocket pieces, and are either finished with a plumb cut
at the other, front end, or with a shallow plumb cut and
a seat or soffit cut. Mostly, eyebrow eaves’ rafters are left
visible, but can be found covered up with a soffit lining.
Whether visible or not, a strip of 6 mm WBP plywood
will be required, either for fixing on top of the rafters in
the area of the projecting eaves, if the rafter-ends are left
visible, or for shaping to a diminish and fixing on the
underside of the rafters, if it is to be lined with a soffit.
12.20.16 Finding the Angles
Figure 12.44(h): The illustrations used here assume
a main roof pitch of 50⬚ and a pitch of 35⬚ for the
eyebrow rafters. The main angle required is for the
sprocket cut. Thinking of this, as illustrated, in the form
of right-angled triangles, the cut for this very acute
angle would be
a ⫺ b ⫽ 50⬚ ⫺ 35⬚ ⫽ 15⬚
Also illustrated is the setting out from a roofing instrument, to provide an alternative way of visualizing the
angle required. If a soffit seat-cut is needed, we already
know this to be 35⬚ and, therefore, a plumb cut, if
required, would be 90⬚ ⫺ 35⬚ ⫽ 55⬚.
12.20.17 Finding the Lengths
On this type of roof, a practical approach to finding
the diminishing rafter-lengths will be more expedient.
One way of doing this, is to establish the longest rafter
in the crown position and then use it as a guide to
finding the length of its neighbour on each side. First,
cut the 15⬚ sprocket angle on one end and lay the
rafter in position, resting in the profile cutout and on
the main rafter. Because the sprocket cut is shallow
and therefore long, small adjustments up or down until
the cut is properly seated will ensure that the rafter is
at its required angle of 35⬚. Now fix this position with
a temporary nail. At the eaves’ end, judge the approximate amount of projection required, with a margin for
error of, say 100 mm, and mark for the initial cut. If
considered necessary, check this by squaring down to a
point near the apron upstand, as indicated at A–B–C
in Figure 12.44(g).
12.20.18 Cutting and Fixing the
Eyebrow Rafters
The first rafter is now removed and tried in the cutouts
on either side and, again, a judgement is made regarding the approximate amount of projection required.
The side of the rafter is marked accordingly and the
marked length is transferred to other timbers to make
two more rafters. Rafter number one can now be fixed
back in place with the temporary nail through the
sprocket-cut again. Newly cut rafters two and three
can now be used to determine the diminished length
of the next pair, rafters four and five. Then rafters two
and three can be fixed like rafter number one with a
temporary nail through the sprocket-cut into the main
rafters. This sequence is carried on down the eyebrow
shape in pairs of rafters, one on each side of the crown
position, until the ends are reached at main-roof level.
Only the sprocket-cut ends are nailed, the other ends
should be unfixed for now, resting in the cutouts.
12.20.19 Marking the Eaves’ Edge
The precise eaves’ edge can now be determined, as mentioned earlier, by pinning down a strip of 6 mm plywood
over the rafter-ends of the eyebrow and marking the
Angle
required
40°
55°
a
b
50°
90°
Main roof pitch 50°
35°
Eyebrow roof pitch 35°
90°
50°
Angle required = a – b = 50° – 35° = 15°
35°
50°
50° – 35° = 15°
Setting out from roofing instrument
Figure 12.44 (h) Finding
the angles
Eyebrow Windows
line on each rafter-top. This task can be made easier
by using the three points A1, A2 and B, referred to in
Figure 12.44(g). First, on each extreme of the eyebrow,
at the lowest and smallest sprocket, mark points A1 and
A2 and projecting, say, 75 mm from the vertical face of
the sheathed window. Strike a line across the tops of the
trimmed rafters from point A1 on one side to point A2
on the other and mark the line midway at A3. Now
square up from this middle point A3 to mark point B on
the eyebrow rafter in the crown position. This can be
done with a straightedge, with one end resting on midpoint A3 and the other being adjusted at point B up
against a roofing or try-square. These three points,
marked on the rafter-tops, greatly assist in positioning
the ply and establishing the eaves’ edge.
allow the outer edge to be trimmed against the rafterends, if necessary. When the eaves’ cuts are known or
have been decided, marked out, cut and completed, refix
the eyebrow rafters in their previous positions, adding a
few more 100 mm wire nails as final fixings.
12.20.22 Fixing Side-support Studs
Figures 12.44(j) and (k): The final studwork directly
behind the sheathing consists of two vertical studs per
B
12.20.20 Eaves’ Finish
T
M
Alternative
finish
Open eaves
Open eaves
Shaped
fascia board
I
Closed eaves
Figure 12.44 (i) Eaves’ finish
Figure 12.44(i): Next, remove the temporarily nailed
rafters and mark and cut the required eaves’ finish,
related to the eaves’-edge line just established. Three
optional finishes are shown in Figure 12.44(i). The
two open-eaves details are most common and seem to
be more in keeping with the aesthetics of eyebrow
windows. The 6 mm WBP plywood is shown fixed on
top of the rafters, to give a better visual finish on the
exposed underside. This has to be wide enough to
mask the greatest projection at the crown. A tilting fillet is also fixed at the eaves’ edge, to give the required
uplift to the eaves’ tiles. This may need a few strategic
half-depth saw cuts to ease it around the serpentine
shape, on top for hollows and on the underside when
going over the crown.
12.20.21 Closed Eaves
The closed-eaves detail in Figure 12.44(i) requires a
narrow fascia board, backed up by a tilting fillet, as
shown. The fascia board, of about 75 mm width and
normal thickness, must be shaped to follow the eyebrow
curvature. The soffit lining, of 6 mm WBP plywood,
needs to be fixed to a level seat cut – to be less problematic geometrically – and is best fixed before the fascia to
173
Figure 12.44 (j) Studding on window beam
Eyebrow
rafter
B
T
Main rafter
B
A
Figure 12.44 (k) Studding on rafter and floor plate
174
Constructing Traditional and Modern Roofs
eyebrow rafter and a row of staggered noggings. The
first, vertical stud B, is a side-support stud which, as
shown, either rests squarely on the ceiling joist, when
the studding is on the window beam, or rests squarely
on the floor plate which continues through on each side
of the window opening. With the sheathing/template
still in position, studs B should now be cut and fixed.
They are cut with a square-ended allowance, to project
at the top, skew-nailed at the base and side-fixed to
the eyebrow rafters. Side-fixings should also be made
where studs B rest against main-roof rafters (Figure
12.44(k)).
with 50 mm round-head wire nails at approximately
200 mm centres and cut off the square-ended projections of studs B, flush to the top of the eyebrow rafters,
following the top edge of the sheathing/template.
12.21 LEAN-TO ROOFS
175 ⫻ 25 mm ridge board spiked to wall
100 ⫻ 50 mm rafters at 400 mm c/c
12.20.23 Fixing Load-bearing Studs
Now that the eyebrow rafters are supported by the
side-support studs B, the sheathing/template can be
removed, if considered necessary, to facilitate the fixing
of studs T, which tend to get more awkward to fix as
they diminish in height. These studs are load-bearing
studs which, as shown, are cut with an acute angle at
the top to fit under the eyebrow rafter and either rest
squarely at the bottom, on the window beam, or are cut
with another acute angle to rest on the main-roof
rafter. With an eyebrow pitch of 35⬚, the top angle
would be 90⬚ ⫺ 35⬚ ⫽ 55⬚; and with a main roof pitch
of 50⬚, the bottom angle would be 90⬚ ⫺ 50⬚ ⫽ 40⬚.
Whether removing the sheathing/template or not,
studs T, when cut and fitted, should be side-fixed to
studs B, skew-nailed to the window beam, where
applicable, and an edge-fixing nail should be driven
through the sharp point of the acute angles. 100 mm
round-head wire nails should be used throughout.
12.20.24 Fixing Final Noggings and
Sheathing
Struts and
hangers
every 4th
or 5th rafter
150 ⫻ 75 mm purlin, built
into gable wall at each end
Binder
Figure 12.45 Traditional lean-to (double) roof
Figure 12.45: This type of roof, usually found on parts
of the building that extend beyond the main structure,
comprises mono-pitched rafters leaning on the structural wall in various ways. This connection to the wall
was usually in the form of a wall plate resting on
wrought-iron corbels built into the wall at about 1 m
centres, or a wall plate bedded on continuous brick
corbelling, projecting from the face of the wall. If the
potential thrust of a particular lean-to roof can be discounted, the connection may be simply a ridge board
fixed to the wall to take the plumb cuts of the rafters.
12.21.1 Ceiling-joists Connection
Figure 12.44 (l) Staggered noggings
Figure 22.44(l): To give the studded eyebrow structure
more rigidity, 100 ⫻ 50 mm noggings should be cut in
and fixed as near to the top as possible, as indicated in
the exposed elevational view. Because the noggings
should be kept in a horizontal position, they will take
on a staggered appearance. Finally, fix the
sheathing/template to the whole studded structure
Traditionally, ceiling joists were built in or cut into the
main wall. Nowadays, TW type joist hangers could be
used. Technically, without purlins, this roof would be
termed a single roof and would be restricted to a span
of about 2.4 m.
12.22 CHIMNEY-TRIMMING
AND BACK GUTTERS
Figure 12.46: When a chimney stack passes through a
roof, the rafters are trimmed around it in a similar way
Trussed Rafters
Tilting fillet and
boarding to form
back gutter
∗
Triangular
firring blocks
fixed to foot of
trimmed rafters
A
A
B
∗ Trimming and
trimmer rafters
must be at least
40 mm from
chimney stack
as per Part L
of the Building
Regulations
175
B
C
D
Plate
connector
D
(a)
A
A
B
C
D
B
C
D
C
Figure 12.46 Chimney trimming and back gutter
(b)
to trimmed openings for dormer or eyebrow windows
and skylights. The trimmer rafters can be stop-housed,
fixed with TT type joist hangers, CL type framing
anchors, or simply butt-jointed against the trimming
rafters – and may be vertical or leaning to the roof
pitch. The former position is preferred, as this allows
the trimmed rafters a birdsmouth bearing on the trimmers. Triangular blocks, boarding or sheeting material,
as illustrated, form the usual back gutter to the stack.
12.23 TRUSSED RAFTERS
Figure 12.47 (a) The Fink or W truss; (b) the fan truss
current information given in the technical manuals
obtained from Gang-Nail Systems Ltd, a member
company of International Truss Plate Association.
●
●
12.23.1 Introduction
As mentioned briefly in the beginning of this chapter,
roofing on domestic dwellings now predominantly
comprises factory-made units in the form of triangulated frames referred to as trussed rafters. These assemblies are made from stress-graded, prepared timber, to a
wide variety of configurations according to requirements. Most shapes have a named reference and the
two most common designs used in domestic roofing are
the Fink or W truss, and the Fan truss. All joints are
butt-jointed and sandwiched within face-fixing plates
on each side. These plates are usually of galvanized steel
with integral, punched-out spikes for machine-pressing
onto the joints. After initial positioning of the trusses,
they must be permanently braced.
12.23.2 Bracing
Figures 12.47(a) and (b): The bracing-arrangement
details given here and in the illustrations – as well as
the other references to truss rafters – are based on
●
●
Braces A: 75 ⫻ 25 mm or 100 ⫻ 25 mm temporary
longitudinal bracing, used to stabilize the position
of the trusses during erection.
Braces B: 97 ⫻ 22 mm (minimum size) permanent
diagonal bracing, forming 45⬚ angles to the rafters,
should run from the highest point on the underside
of a truss to overlap and fix to the wall plate, starting at a gable end and running zigzag throughout
the length of the roof, fixed to every truss with two
3.35 mm ⫻ 65 mm long galvanized wire nails.
There should be not less than four braces (two on
each slope) of any short-length duopitched roof.
All joins of incomplete bracing-lengths should be
overlapped by at least two trussed rafters. The angle
of bracing given above as ideally 45⬚, should not be
less than 35⬚ or more than 50⬚.
Braces C: 97 ⫻ 22 mm (minimum size) permanent
longitudinal bracing, with fixings and overlap
allowances as for diagonal bracing, positioned at all
node points (points on a truss where members intersect), with a 25 mm offset from the underside of
the rafters (top chords) to clear the diagonal bracing, extended through the whole length of the
roof and butting tight against party or gable walls.
Braces D: 97 ⫻ 22 mm (minimum size) permanent
diagonal web chevron bracing, each diagonal
extended over at least three trusses, required for
duo-pitched spans over 8 m and monopitched
spans over 5 m.
176
Constructing Traditional and Modern Roofs
12.23.3 Advantages
One of the advantages of trussed-rafter roofs is the
clear span achieved, without the traditional need for
load-bearing partitions or walls in the mid-span area.
Another advantage, to the building designer, is that
the specialist truss-fabricator will only need basic
architectural information to plan the truss layout in
detail for the building designer’s approval.
12.23.4 Site Storage and Handling
It is important to realize that although the trusses are
strong enough to resist the eventual load of the roofing materials, etc., they are not strong enough to resist
certain pressures applied by severe lateral bending.
These pressures can have a delaminating effect on the
metal-plated joints and are most likely to occur during
truss delivery, movement across the site, site storage
and lifting up into position – especially the motion of
see-sawing over the top edges of walls when the truss
is laying on its side face.
Recommendations
Storage on site should be planned to be as short a time
as possible, preferably not more than 2 weeks. In bad
weather, stored trusses should be protected by a waterproof cover, arranged to allow open sides for air ventilation. The trusses should be stored on raised, level
bearers to avoid distortion and contact with the ground.
Vertical Storage
This is the preferred method. The trussed rafters are
stored in an upright position, stacked close together
against a firm, lean-to support at each end, resting on
bearers at the position where the wall plates would
normally occur, built up to ensure that any eaves’ projection clears the ground and any vegetation present.
Horizontal Storage
This alternative method, where trussed rafters are laid
flat, stacked up upon each other, requires a greater
number of bearers which should be carefully arranged
to give level support at close centres and be directly
under every truss joint. This is to reduce the risk of
joint-damage and long-term deformation of the
trusses. If subsequent sets of bearers are used higher up
in the stack to take another load of trusses, the bearers
must be placed vertically in line with those below.
frames, resembling braced stud-partitions, are secured
with raking struts and are set up parallel to each other
and at the same span as the roof ’s wall plates (the
length of the bottom chord or ceiling tie). The height
of the two side frames must be more than the rise of
the roof, to ensure that the apex of the upside-down
trusses clears the ground.
Manhandling
On wide-span trusses – which are more liable to jointdamage from sideways-bending – it may be necessary
to use additional labour to provide support at intermediate positions. When carrying trusses across the site,
it may be safer and more manageable for a truss to be
reversed so that the apex hangs down. On the other
hand, when being offered up into its roof position, the
truss should be upright and the eaves’ joints should be
the main lifting points. Laying trusses on their sides
and pushing/pulling/see-sawing them across walls and
scaffolding, etc., may make manhandling them easier,
but is a completely unacceptable practice.
Mechanical Handling
When mechanical means are used, the trusses should
be lifted in banded sets and lowered onto suitable supports. The recommended lifting points are at the
rafter (top chord) or ceiling tie (bottom chord) node
points (where the joints occur). Lifting single trusses
should be avoided, but if unavoidable, a suitable
spreader bar should be used to offset the sling-forces.
12.23.5 Providing Profiles for
Gable Ends
Figure 12.48: Gable-end walls are usually completed,
or partially completed, before the trussed-rafter roof is
∗
∗
Brace
each side
∗ Ridgeboard offcut
can project to hold
the bricklayer’s line
Inverted Storage
A third method of storage, preferred by some manufacturers and builders, is to invert the trussed rafters
and support them on built-up side frames. These
Figure 12.48 Profile erected for gable end
Hipped Roofs Under 6 m Span
erected. When this happens, a single trussed rafter
frame or – if the trussed rafters are not yet on site – a
pattern pair of common rafters, as illustrated, is fixed
and braced up at each gable end to act as a profile for
the bricklayer to use as a guide in shaping the top of
the raking walls. If gable ladders (described later) are
to project over the face of the wall, then the brickwork
should be built up only to the approximate underside
of the truss and completed after the ladders have been
fixed in position.
12.24 ERECTION DETAILS AND
SEQUENCE FOR GABLE ROOFS
12.24.1 Wall Plates and Restraint
Straps
Wall plates for trussed rafters are jointed and bedded
as already described for traditional pitched roofs. The
next step is to mark the positions of the trusses at
maximum 600 mm centres along each wall plate. This
will indicate the clear areas for the positioning of the
vertical restraint straps, which are now fixed.
177
fixing, the first truss is fixed to the wall plates, in a
position approximately equal to the first pair of common rafters in a hipped end. This determines the apex
for the diagonal braces, marked B. Stabilize and
plumb the truss by fixing temporary raking braces E
on each side, down to the wall plates.
Fix temporary battens A, on each side of the ridge
and resting on the gable wall. Position the second
truss and fix to the marked wall plate and to the temporary battens A, after measuring or gauging to the
correct spacing. Proceed until the last truss is fixed
near the gable wall. Now fix the diagonal braces B
with two 3.35 mm ⫻ 65 mm galvanized round wire
nails per fixing and then continue placing and fixing
trusses in the opposite direction, braced back to the
first established end. Finally, fix the braces marked C
throughout the roof ’s length and fix horizontal
restraint straps at maximum 2 m centres across the
trusses onto the inner leaf of the gable walls, as illustrated previously in Figure 12.37(e).
12.25 HIPPED ROOFS UNDER
6 m SPAN
12.24.2 Procedure
A
Gable
wall
B
Each
side
A
C
C
C
Second truss
First truss
E
E
Figure 12.49 Erection of Fink trussed rafters
Figure 12.49: The erection procedure is open to a certain amount of variation, providing care is taken in
handling and pre-positioning the trusses on the roof.
Bearing that in mind, the following procedure is based
on the notes given in the technical manual on trussed
rafters, mentioned on page 175.
By using framing anchor truss clips (the recommended fixing, which does not rely on the high degree
of skill required for successful skew-nailing) or by
skew-nailing from each side of the truss with two
4.5 mm ⫻ 100 mm galvanized round wire nails per
Girder of
standard trussed
rafters
Figure 12.50 Hip-end construction for roof under
6.0 m span
Figure 12.50: As illustrated, the recommended hipend for a roof of this relatively small span is of traditional construction. The main difference being that
instead of the saddle board and hips being fixed to a
ridge board and the first pair of common rafters, they
are fixed onto a girder truss made up of manufactured
truss rafters. This consists of two or three standard
trussed rafters securely nailed together by the supplier
(preferably), or fixed on site to a nailing pattern stipulated by the supplier.
178
Constructing Traditional and Modern Roofs
12.25.1 Procedure
After the wall plates are jointed, bedded and set, the
hipped ends are set out as already described for traditional roofing, the positions of the standard trusses
marked and the vertical restraint straps positioned and
fixed. The erection sequence starts with the fixing and
temporary bracing of the girder truss, followed by the
infill of the standard trusses and bracing. The hip ends
are then constructed, using hip rafters and jack rafters
of at least 25 mm deeper section than the truss rafters
to allow for birdsmouthing to the wall plates. Ceiling
joists – unlike those illustrated – may also run at
right-angles to the multiple girder truss, supported on
the girder truss by minihangers.
12.26 HIPPED ROOFS OVER
6 m SPAN
∗ Hip monotrusses
Hip
girder
trusses
Purlin
and
struts
infill ceiling joists are laid and fixed. In three positions, as illustrated, other special trusses rest across the
ceiling joists and are fixed to them and to the vertical
members of the girder truss. These secondary trusses
are known as hip mono trusses and six are required at
each hip end. Two in the centre are nailed together with
rafter-thickness packings in between and fixed in position to straddle the central vertical girder member –
and house a half-length flying crown rafter. The other
hip mono trusses, nailed directly together in pairs,
without packings, are fixed at the quarter-span position on each side of the girder truss and are splay-cut
like jack rafters to fit the hip rafters. A short purlin
and vertical struts, as illustrated, are fixed to the mono
trusses. Hips and jack rafters, as before, must be at
least 25 mm deeper to allow for birdsmouthing to the
purlin and wall plates.
12.27 ALTERNATIVE HIPPED
ROOF UP TO 11 m SPAN
Figures 12.52(a)–(c): The most common construction
for a hipped roof up to this span is referred to as a
standard centres hip system. It is made up of a number
X
3
2
∗
∗
Hip girder
truss
1
3
A
2
A
1
∗
∗
∗
∗
A
Figure 12.51 Hip-ended construction for roof over
6.0 m span
B
Figure 12.51: There are various alternative methods of
forming hip ends in trussed rafter roofs. The example
given here, therefore, is just one of the methods that
deal with large spans. Assuming that the wall plates
have been jointed and bedded and are now set, the
erection procedure is as follows.
B
B
1
B
B
B
B
X
Figure 12.52 (a) Standard centres hip system
12.26.1 Procedure
Three special trusses, known as hip girder trusses, are –
as mentioned for the previous hip end – securely
nailed together by the supplier (preferably), or fixed
on site to a nailing pattern stipulated by the supplier.
The girder is fixed at the half-span (run) position and
Figure 12.52 (b) Flat-top hip truss (in position A)
Gable Ladders
12.28 VALLEY JUNCTIONS
Flying crown rafter
Top chord bracing
Diminishing valley
frames
Central
mono1
truss B
A
1
179
2
A
A
3
1
2
Valley lay boards
3
Multiple truss
Figure 12.52 (c) Section X–X
of identical flat-top hip trusses A (Figure 12.52(b))
spaced at the same centres as the standard trusses, and
a multiple girder truss of the same profile which supports a set of monopitch trusses B, set at right-angles
to the girder. The corner areas of each hip are made
up of site-cut jack rafters and infill ceiling joists
attached to the hip girder. The flat tops (chords) of
the hip trusses require lateral bracing back to the multiple hip girder.
12.27.1 Procedure
Assuming that the wall plates have been marked out
for the hip end(s) and the truss positions, and that the
vertical restraint straps have been fixed, a standard
truss is first fixed at the half-span (run) position,
labelled 1 in the illustration. The remaining standard
trusses (2, 3 etc.) are then erected and braced. A
ledger rail of 35 ⫻ 120 mm section – instead of a saddle board – is fixed at the apex of truss 1, at a height
to suit the hip rafter’s depth.
Next, the multiple girder truss A1 is fixed, set in
from the hip end by the span (length of bottom
chord) of the mono truss B; then the two intermediate
flat-top hip trusses, A2 and A3, are fixed and braced.
Now a string line is set up, representing the in situ
position of the hip rafters, and the flying rafters of the
flat-top hip trusses are marked and cut back, allowing
for the hip rafter’s thickness. Next, the central mono
truss B1 is fixed, after its flying rafter has been
trimmed and notched onto the ledger rail and its bottom end has been fitted into a prefixed truss shoe
attached to the bottom chord of the girder. Now the
hip rafters can be cut to length, birdsmouthed,
notched and fixed in position. The remaining mono
trusses B are then fitted and fixed into pre-fixed bottomchord truss shoes, after trimming the flying rafter of
each, ready for fixing to the hip rafter. Finally, the corner areas of each hip are completed with loose ceiling
joists attached to the girder truss with mini hangers and
loose infill jack rafters.
Multiple
girder truss
Standard
trusses
A
Girder
truss
shoe
Figure 12.53 Valley junctions
Figure 12.53: Where a roof is so designed as to form
the letter T in plan, a valley set, known as diminishing
valley frames (as illustrated), can be fixed and braced
directly onto the main trussed rafters in relation to lay
boards or inset noggings. The noggings are required
when the ends of the valley frames do not coincide
with an underlying truss position. Lay boards or battens, running along the edges of the valley, are normally required by the roofer as a means of attaching
the splay-cut ends of the tiling battens that are fixed at
right-angles to the trusses.
12.28.1 Intersecting Girder Truss
At the intersecting point marked A, where the offshoot roof meets the trimmed eaves of the main roof –
if no load-bearing wall or beam exists at this position –
it will be necessary to have a multiple girder truss.
This is to carry the ends of the trimmed standard
trusses via hangers known as girder truss shoes (Figure
12.53). The girder is formed, either in the factory or
on site, by nailing three intersection girder trusses
together to a stipulated nailing pattern. Because of
the heavy loads being carried, it may be necessary for
the girder truss to have larger bearings in the form of
concrete padstones.
12.29 GABLE LADDERS
Traditionally, when a verge projection was required on
a gable end, this was achieved by letting the ridge
board, purlins and wall plates project through the wall
180
Constructing Traditional and Modern Roofs
by the required amount – usually about 200 mm – to
act as fixings for an outer pair of common rafters and
the barge boards.
B
Framing anchors
on underside
B
12.29.1 Modern Method
D
A
E
D
C
Figure 12.55 Forming roof trap
Figure 12.54 Gable ladders
Figure 12.54: As trussed-rafter roofs do not have
purlins or ridge boards, the verge-projection is
achieved by fixing framed-up assemblies, known as
gable ladders, directly onto the first truss on the inside
of the gable wall, as illustrated. The ladders, supplied
by the truss manufacturer, are fixed on site by nailing
at 400 mm centres and are subsequently lined with a
soffit board on the underside and barge boards on the
face side, after being built-in by the bricklayer. The
usual practice is for the gable wall to be built-up to the
approximate underside of the end truss, then completed after the ladders have been fixed.
12.30 ROOF HATCH (TRAP)
When trusses are spaced at 600 mm centres, it should
be possible to simply fix trimmer noggings between
the bottom chords of the trusses to form the required
roof-trap hatch. In other cases, when the trusses are
closer together or a bigger hatch is required, it will be
necessary – but not desirable – to cut the bottom
chord of one of the trusses, as illustrated.
trimming joists. Next, two 150 ⫻ 38 mm boards B,
spanning three trusses, must be fixed in position on
each side of the proposed trap hatch before the central
ceiling-joist chord is cut. The boards are fixed on the
underside to the side of the ceiling-joist ties with
bracket-type framing anchors and 31 mm ⫻ 9 gauge
square-twisted sherardized nails, as per the manufacturer’s instructions. The central chord C is then cut,
and the opening trimmed with two trimmers D and,
if required, an infill joist E.
12.31 CHIMNEY TRIMMING
Figure 12.56: Where the width of a chimney is greater
than the normal spacing between trussed rafters, the
trusses may have a greater spacing between them in the
area of the chimney stack, providing the increased spacing is not more than twice the normal truss spacing.
Short purlins
each side
Short binder
∗∗
∗ Short trimmer
∗
∗∗ Infill rafter
each side
∗∗
12.30.1 Procedure
Figure 12.55: Typical details are shown for forming a
trap hatch in the central bay of the trussed rafters.
First, 35 mm thick framing timbers A are fixed to the
inside faces of the ceiling joists that will be acting as
Infill
ceiling joist
each side
∗
Figure 12.56 Chimney trimming
∗
Purlin support
Water-tank Supports
As illustrated, the non-truss open areas remaining on
each side of the chimney stack are filled in with loose
infill rafters, ceiling joists, trimmers, binders and short
purlins strutted against the webs of the nearest standard
trusses on each side.
As per the Building Regulations, the timbers
should be at least 40 mm clear of the chimney stack.
The infill rafters, which are nailed to the side of the
infill joists and to the wall plate, should be at least
25 mm deeper than the trussed rafters to allow for a
birdsmouth to be formed at the wall plate.
12.32 WATER-TANK SUPPORTS
Figure 12.57: For domestic storage of 230 or 300 litre
capacity, the load is usually spread over three or four
trusses. The details illustrated here are those recommended for a 300 litre tank within a Fink or W truss
roof of up to 12 m span.
12.32.1 Spreader Beams
Two spreader beams of 47 ⫻ 72 mm section extend in
length over the bottom chords of four trusses, as illustrated, up against the web on each side (close to the
node points), sitting vertically on edge, not flat. The
permanent longitudinal bracing, which is normally in
this position, is offset in this area and fixed at the
sides, up against the spreader beams.
181
12.32.2 Cross-bearers
Two cross-bearers of 35 ⫻ 145 mm section are now
skew-nailed to the spreader beams, positioned at onesixth the distance of the beam’s bearing-length from
each end – which is midway between the spacings of
the first and second truss and the third and fourth
truss in contact with the spreader beam.
12.32.3 Tank Bearers and Base
Board
Next, two tank bearers of 47 ⫻ 72 mm section are
skew-nailed across the first bearers, relative to the tank
width, and a WBP plywood base board – not chipboard – is fixed to these. Like the spreader beams, the
cross-bearers and tank bearers must sit vertically on
edge, not flat.
12.32.4 Alternative Tank Support
If more headroom is needed above the tank platform,
an alternative tank-bearer frame, the same or similar
to that illustrated, may be used. This is made up of
joist hangers and/or truss shoes, so the deeper crossbearers, being parallel and between the trusses, can be
dropped lower if required, on pre-positioned joist
hangers. To allow for long-term deflection, there
should be at least 25 mm between cross-bearers and
the ceiling and the same between tank bearers and the
ceiling ties of the trusses.
Tank
Tank
Plywood
base board
Tank bearers
Cross-bearers
Spreader beams
Alternative tank-bearer frame
Cross
bearer
Tank
bearer
Figure 12.57 Water-tank
supports
182
Constructing Traditional and Modern Roofs
12.33 WORK AT HEIGHT
REGULATIONS 2005
These regulations from HSE (Health and Safety
Executive) are only briefly outlined here, but are essential reading in their entirety for anyone working (or
responsible for others working) at heights. In the construction industry, this covers any operation – not just
roofing – where there is a risk of falling, whether it be
from a low height or from a great height. The majority
of fatal and serious injuries in industry are from falls –
and over 53% of the serious injuries are from low
heights.
The onus of responsibility is on the employer and/or
his representative (the duty holder), to carry out risk
assessments and issue safety-method statements to all
concerned with the work at height. By issuing methodstatements, a share of the responsibility is passed on to
employees (or sub-contractors), who must be responsible for their actions. The main key to ensuring safe
working is identified as evaluating risks in a hierarchy of
risk assessment. The order of the hierarchy is:
●
●
AVOID working at height, if possible. For example,
consideration might be given to prefabricating a
truss rafter roof – or a section of it – at ground level
on site and lifting and placing it onto the structure
by crane. If, after assessment, work at height cannot
be avoided, then:
PREVENT a possible fall by erecting adequate
scaffolding and work platforms with guard rails and
●
toe boards, etc., to provide edge protection. Bear in
mind that when erecting a roof, a scaffold around
the outside does not prevent falls into the open well
of the building. Alternatively, on small, isolated
jobs, consider using a MEWP (mobile elevated
working platform) – or a tower scaffold, instead of
working from a ladder. Ladders might be the easy
way, but they are not usually the safest way to do a
job. If none of these are practicable, then:
MITIGATE the effects of a fall by minimizing the
fall-distance and thereby the consequences by providing safety nets just below the work area, or air
bags on the floor level below. The safety nets must
be installed by competent riggers.
In certain situations, additional measures may be
necessary, such as providing fall-arrest equipment in
the form of a safety harness – which must be securely
attached to a strong anchorage point. To minimize
trauma of suspension in a fall situation, a rescue plan
should be part of the safety-method statement.
Although there is mention of a 2 metre rule applying before guard rails are legally required on a scaffold,
risk assessment of falls is still required below this
height and sensible, pragmatic precautions are
expected to be taken. Mention is made of a knee-high
kick stool, such as a traditional hop-up, not having to
conform to the regulations, providing it is stable and
in a good condition.
13
Erecting Timber Stud
Partitions
13.1 INTRODUCTION
Partitions are secondary walls used to divide the internal
areas of buildings. Although often built of aerated
building blocks, other materials, including timber and
metal, are frequently used – especially above groundfloor level, on suspended timber floors, where block
partitions would add too much weight unless supported from below by a beam or a wall.
13.2.1 Jointing Arrangement
The main frame of this type of partition was throughmorticed, tenoned and pinned (wooden pins or nails);
the intermediate uprights (studs) were stub-tenoned
to the head and sill; the door head was splay-housed
and stub-tenoned to the door studs; the door studs
were dovetailed and pinned to the sill; and the staggered noggings were butt-jointed.
13.2 TRADITIONAL
BRACED PARTITION
13.3 TRADITIONAL TRUSSED
PARTITION
Figure 13.1: This is only shown for reference and comparison with the modern stud partition illustrated in
Figure 13.3 and the trussed partition seen in Figure
13.2. The partition was made up of 100 ⫻ 75 mm head,
sill(s), door studs and braces – and 100 ⫻ 50 mm intermediate studs and noggings. The diagonal braces, which
were bridle jointed to the door studs and sill, were
included partly to give the partition greater rigidity
against sideways movement; and partly to carry some of
the weight from the centre of the partition down to the
sill-plate ends, which were housed into the walls.
Figure 13.2: As with the above braced partition, the
trussed partition, with the advent of modern materials
and methods, has been obsolete for many years. It was
used for carrying its weight and the weight of the
floor above. This should be taken into account before
commencing any drastic alterations or removal on
conversion works – as these partitions can still be
found in older-type buildings.
Note that timber partitions are now referred to as
stud partitions, or studding (derived from old English
studu, meaning post).
200 ⫻ 100 head
200 ⫻ 100 Intertie
25 mm
diameter
bolts
150 ⫻ 100 sill
Figure 13.1 Traditional braced partition
Figure 13.2 Traditional trussed partition (100 ⫻ 100 mm
door posts, braces and straining heads; 100 ⫻ 50 studs
and noggings)
184
Erecting Timber Stud Partitions
13.4 MODERN STUD
PARTITION
13.4.2 Head Plate
Figure 13.3: The position for the head plate B can be
fixed by plumbing up to the ceiling from the side of the
sill at each end, either with a pre-cut wall stud and
spirit level, a straightedge and spirit level, or a plumb
bob and line, then by snapping a chalk line across the
ceiling. The head plate is then cut to length, set out
with intermediate stud-positions and propped up with
two or three temporary uprights – purposely oversize in
length – as illustrated in Figure 13.4. The plate is fixed
to the ceiling joists with 100 mm round-head wire nails.
Figure 13.3: Although these partitions can be made in
a joinery shop and re-assembled on site, with certain
tolerances made for the practicalities involved, the
common practice nowadays is to cut and build them
up on site (in situ), piecemeal fashion. The detailed
sequence of doing this is given below.
13.4.1 Sill (or Floor) Plate
Set out from
doorway
Fixed sill
Figure 13.3: The sill, labelled A on the illustration is
cut to length and, if straight, can be used for setting
out the floor position. Alternatively, its position
can be snapped on the floor with a chalk line
related to tape-rule measurements. The position
of any door opening must be deducted from the
sill plate setting-out. This deduction is an
accumulation of
Lay head plate against fixed sill and set out stud positions
Mark and fix head plate
2
door width (say 762 mm)
thickness of door linings (say 28 mm ⫻ 2)
a fitting tolerance (say 6 mm)
door studs (50 mm ⫻ 2)
to give a total of 924 mm.
The plate is fixed to joists with 100 mm roundhead wire nails, or to floor boards or panels with
75 mm nails or screws, or to concrete or screeded
floors with nylon-sleeved Frame-fix or Hammer-fix
screws, or cartridge-fired masonry nails or bolts, at
approximately 900 mm centres.
1
3
Figure 13.4 Marking and fixing the head plate
13.4.3 Wall Studs
Figure 13.3: The wall studs C should be marked to
length either by a pinch-stick method (Figure 13.5(a))
F
B
E
C
F
F
F
F
F
F
F
G
G
G
G
G
G
G
G
F
2.4 m
F
C
D
D
G
G
1.2 m
G
A
A
etc.
A to G is the recommended sequence of erection
Figure 13.3 Modern stud partition
400
400
400
Modern Stud Partition
Mark
Pinch
stick
Head
Wall stud
skew-nailed
Stud
Hand
pressure
(a)
185
Sill
(b)
(c)
or by offering up a slightly oversize stud, resting on
the floor plate and marked at the top, as indicated in
Figure 13.5(b). Add l–2 mm for a tight fit, then cut to
length and fix to the block-wall with 100 mm Framefix or Hammer-fix screws. There should be at least
three wall fixings and the ends of the stud should
be skew-nailed to the plates, as shown in
Figure 13.5(c).
Figure 13.5 (a) Pinch stick method;
(b) oversize stud method; (c) skew nail to plates
Spirit level
Door
stud
Door
stud
13.4.4 Door Studs
Figure 13.3: The door studs D are now marked, as
above, from floor surface to the underside of the head,
tightening-allowance added, then cut, carefully plumbed
and fixed. The base of each stud is fixed with two
100 mm round-head wire nails, driven slightly dovetailfashion into the end of the floor plate and one central
75 mm nail skew-nailed into the floor. At the top, each
stud is skew-nailed with three 75 mm wire nails, using
the skew-nail technique indicated in Figure 13.6.
A B
1 Drive in
supportnail on
one side
B C
2 Fix stud on
other side with
two skew-nails
A B
3 Remove support-nail
Figure 13.7 Mark head-housing
13.4.5 Door Head
Figure 13.3: Next, the position of the door head E is
marked on the door studs, as illustrated in Figure 13.7.
The measurement required for this is an accumulation
of the door height (say 1.981 m) plus tolerance for
floor covering (if carpet, say 15 mm) plus head-lining
thickness (say 28 mm), giving a total of 2.024 m. This
can be marked each side, but is best marked on one
side of the door opening, then transferred across with a
spirit level. If the head is to be butt-jointed and nailed
(which is the most common trade-practice, see Figure
13.9(d)), cut to length to equal the width between
studs at floor-plate level, or 924 mm (example measurement) as worked out in Section 13.4.1, and fix
through the door studs with two 100 mm round-head
wire nails each side. Alternatively, if to be housed (see
Figure 13.9(b)) add 24 mm to the length, mark and cut
the 12 mm deep door-stud housings each side in situ,
working from a saw stool or steps, slide the head into
the housings and fix through the door studs with two
75 mm round-head wire nails each side.
A B
13.4.6 Intermediate Studs
4 Use supportnail to fix side ‘A’
Figure 13.6 Skew-nail technique
Figure 13.3: Studs F are next in sequence, cut to
length for a tight fit as described for wall studs in
Section 13.4.3. If the plates are not already set out for
the intermediate stud positions, as suggested earlier,
186
Erecting Timber Stud Partitions
then these positions should now be marked out to suit
the plasterboard sizes. The boards used are usually
2.4 m ⫻ 1.2 m and either 9.5 mm or 12.5 mm thick.
These sizes dictate the spacing of the studs at either
400 mm centres (6 ⫻ 400 ⫽ 2.4 m) or 600 mm centres
(4 ⫻ 600 ⫽ 2.4 m). The 9.5 mm thickness should only
be used on studding spaced at 400 mm centres. The
studs are nailed into position with three 75 mm wire
nails to each abutment, using the skew-nail technique
shown in Figure 13.6.
13.4.7 Noggings
Figure 13.3: These final insertions are short struts, G,
that stiffen up the whole partition. If they are centred
at 1.2 m from the floor, as shown (by measuring up at
each end and snapping a chalk line), the joint of the
plaster-board will be reinforced against the noggings.
The noggings are cut in snugly and fixed by skewnailing or end-nailing as indicated in Figure 13.8(a).
To lessen the risk of bulging the door studs, the fixing
of the noggings should be started from the extreme
ends, working towards the door opening and being
extra careful with the final nogging insertions.
(a)
(b)
(c)
Figure 13.8 Alternative methods of nogging; (a) straight
noggings; (b) staggered noggings; (c) herringbone
noggings
13.4.8 Studding Sizes
The timber used for studding is usually 100 ⫻ 50 mm
sawn (unplaned) softwood, or ex. 100 ⫻ 50 mm prepared (planed to about 95 ⫻ 45 mm finish) softwood.
For economy, 75 ⫻ 50 mm sawn, or ex. 75 ⫻ 50 mm
prepared is sometimes used. Sawn timber is more
common, but prepared timber is also used a lot nowadays to lessen the irregularities transferred to the surface material. To this end, regularized timber,
machined to a reduced, more constant sectional size, is
available and used for partitions nowadays.
13.4.9 Alternative Nogging
Arrangements
Figure 13.8: Ideally, successive rows of noggings at
600 mm centres vertically (between the 1.2 m spacings
shown in Figure 13.3) should be used to give greater
rigidity and support to the plasterboard, although one
row is normally sufficient. Points for and against the
three alternative nogging arrangements are given below.
13.4.10 Straight Noggings
Figure 13.8(a): These can be positioned to reinforce
horizontal plasterboard joints, but are not the easiest
to fix. Various alternative methods of fixing are indicated by dotted lines denoting the nailing technique.
The technique for skew-nailing (Figure 13.6) can be
used here, with the support nail positioned under the
nogging. Another technique, using a temporary strut,
is shown in Figure 13.19.
13.4.11 Staggered Noggings
Figure 13.8(b): These cannot effectively reinforce the
plasterboard joints, but as indicated, are easier to fix by
end-nailing. Of course, if the plasterboard was placed
on end, with vertical joints being reinforced on the
intermediate studs, there would be nothing against
this method.
13.4.12 Herringbone Noggings
Figure 13.8(c): These are positioned at an angle of
about 10⬚, are easy to fix and achieve a tight fit, even
with inaccurate cutting. If correctly positioned, they
give about 90 per cent reinforcement to the plasterboard joints. On the minus side, this method has a
tendency to bulge the door studs.
13.5 DOOR-STUD AND
DOOR-HEAD JOINTS
Figure 13.9: The strength of these joints is important,
as any weakness, especially resulting in an upwards
Stud Joints to Sill and Head Plate
Splay-housed, morticed and tenoned
Door head
187
displacement from timber which might twist and
from lateral or vertical hammer-blows, is too elaborate
and time-consuming nowadays.
(a)
13.5.2 Quarter-housed and Nailed
(b)
Figure 13.9(b): This is one of the recommended methods and is a good compromise between the other two
extremes. The door-stud quarter housings (i.e. a quarter of the thickness) restrict twisting and upwards
movement of the door-head and if the partition is
well strutted with noggings, lateral movement should
not be a problem.
Quarter-housed (12 mm) and nailed
Door head
Butt-jointed and frame-anchored
Door head
(c)
Butt-jointed and nailed
Door head
(d)
Figure 13.9 Door-stud and head joints; (a) too
elaborate; (b) good compromise; (c) modern method
(d) common method
movement of the door-head stud, can affect the
door-lining head. Problems like this usually occur for
two reasons: if a tolerance gap exists between the
door-head stud and the lining-head; and if the doorhead/door-stud joint is not strong enough to resist
hammer-blows when the door-lining legs are being
fixed at the top, or – more likely – when the door stop
is being fixed to the underside of the door-lining
head. Evidence of movement will appear as unsightly
gaps to the corner housing-joints of the door lining.
The risk of this happening can be avoided by using
the joints shown in Figures 13.9(b) or (c) and by
inserting packing or wedges in the gap between doorhead and lining-head, directly above each door-lining
leg (see also Chapter 6 which covers the fixing of door
frames, linings and doorsets).
13.5.1 Splay-housed, Morticed,
Tenoned and Draw-bore Wedged
Figure 13.9(a): This traditional door-stud/head joint,
although ideal for the job and strongly resistant to
13.5.3 Butt-jointed and
Frame-anchored
Figure 13.9(c): This modern method is also recommended. It has all the virtues of the quarter-housed
joint in restricting movement and is less timeconsuming. The butt-jointed head can be nailed
through the door-studs initially, then the framing
anchors fixed at each end, or the framing anchors can
be fixed in position on the head, the head located and
fixed into the door-studs via the remaining framinganchor connections. The anchors are recommended to
be fixed with 3 mm diameter ⫻ 30 mm-long sherardized clout nails.
13.5.4 Butt-jointed and Nailed
Figure 13.9(d): This method is the most common
trade-practice for attaching door-head to door-studs
but, for reasons already stated, it is not the best. In the
past, it was the method used on cheap work, which
has now become the norm.
13.6 STUD JOINTS TO SILL
AND HEAD PLATE
Figure 13.10: There are four methods of jointing vertical, intermediate studs to the head plate and sill (floor)
plate, as follows.
13.6.1 Stub-tenoned
Figure 13.10(a): The short tenons are morticed to half
depth into the head and sill. This method involves too
much hand work on site and is best suited to preformed partitions being made in the joinery shop,
where machinery is available. Such partitions would
be sent to the site in pieces, designed with length and
188
Erecting Timber Stud Partitions
(a)
(b)
(c)
height tolerances, ready for assembly and erection.
This is useful in occupied premises, such as offices and
shops, where the site work would be reduced.
13.6.2 Housed or Trenched
Figure 13.10(b): The housings are cut into a quarterdepth of the plate thickness and the studs are skewnailed at each joint with two 75 mm round-head wire
nails. This method can be easily handled on site; however, although housings are ideal for easier nailing,
straightening and retaining any twisted studs, the
method is rarely used nowadays because of the added
time element.
(d)
Figure 13.10 Stud joints to
sill or head plate
plate, at about 45⬚, on one line of the stud-position, so
that when the stud is against it, the nail-head protrudes to the side. The stud is then fixed against the
support-nail with two fixings, the support-nail
removed with the claw hammer and used as the
central fixing on the other side.
13.7 DOOR-STUD AND
SILL-PLATE JOINTS
13.6.3 Butt-jointed and
Frame-anchored
Figure 13.10(c): This modern method, already referred
to in Section 13.5.3, has most of the benefits afforded
by housing joints – with the exception of straightening
out a stud already in a state of twist. The studs need to
be fitted tightly and two framing anchors per joint –
one on each opposite face-edge – are nailed into position with 3 mm ⫻ 30 mm sherardized clout nails.
13.6.4 Butt-jointed and Skew-nailed
Figure 13.10(d): Again, this is the most common
trade-practice, not because it is the best, but because it
is the quickest method of jointing. Originally used
only on cheap work, this method is now widely used.
The stud should be a tight fit, otherwise the relative
strength of this joint is very much impaired. Three
75 mm wire nails should be used, two in one side, one
in the other (as shown in Figure 13.6). This technique
requires one support-nail to be partly driven into the
Traditional
Modern
Figure 13.11 Door-stud/sill-plate joints
Figure 13.11: Traditionally, these joints were dovetailed and pinned (dowelled or nailed), as shown, to
retain the base of the door-stud effectively. Studs of
63 or 75 mm thickness were used.
The present-day method uses door studs reduced
to 50 mm thickness, resting on the floor and
butted and nailed against the sill. As described
previously, two 100 mm wire nails are driven slightly
dovetail-fashion into the end of the plate and one
centrally placed 75 mm wire nail is skew-nailed into
the floor.
Corner and Doorway Junctions
13.8 CORNER AND
DOORWAY JUNCTIONS
Corner L-junction
189
between two of the studs, to add rigidity and give
continuity to the rows of noggings. For possible economy of timber and to achieve a similar result, a practical method of using vertical noggings is shown at (c).
This could save a full-length vertical stud, as usually
the noggings required can be cut from offcuts and
waste material.
Doorway L-junction
Alternative Methods
Corner T-junction
Doorway T-junction
Figure 13.12 Corner and doorway junctions
Figure 13.12: This small-scale plan view of a room
might be an uncommon layout for partitioning, but
serves to illustrate the four junctions requiring different treatment. The best treatment each could receive
would involve the use of three vertical studs, but other
treatments shown here are sometimes used.
13.8.1 Corner L-junction
Figures 13.13(a)-(c): The plan view (a) shows the first
choice of construction using three full-length corner
studs to provide a fixing-surface on each side of the
internal angle. As seen in the isometric view (b), short
offcut blocks should be fixed in the gap existing
Figures 13.13(d) and (e): The first alternative (d) is
reasonable, but would involve interrupting the partitioning operation to allow for plasterboard to be fixed
to at least one side of the first partition, before the
second partition could be built. The second alternative
shown at (e) allows the whole partition to be built by
providing a fixing-surface to each side of the internal
angle, in the form of 50 ⫻ 50 mm vertical noggings
fixed between the plates and the normal horizontal
noggings. However, unless these vertical noggings are
housed-in, there is a risk of them being displaced
when plasterboard fixings are driven in.
13.8.2 Doorway L-junction
Figure 13.14: Where a doorway meets a corner
L-junction, the problem of providing fixing surfaces on
the internal angle is the same as before, and a similar
treatment (a), using vertical noggings between normal
horizontal noggings, is used instead of a full-length
stud. The other methods (b) and (c), are similar alternatives to those shown in Figures 13.13(d) and (e) and
the same considerations and comments apply.
∗Vertical noggings
∗
∗
(a)
(b)
(c)
(d)
(e)
Figure 13.13 Corner L-junction
(a)
(b)
(c)
Figure 13.14 Doorway L-junction
190
Erecting Timber Stud Partitions
(a)
(b)
(c)
(a)
(b)
(c)
Figure 13.15 Corner T-junction
Figure 13.16 Doorway T-junction
Provision for Architrave
In good building practice, another consideration at
this doorway junction, is that there should be provision for a full-width architrave on the side where the
architrave is touching the adjacent wall. In practice, 3
or 4 mm less than the architrave width is provided on
the inside angle to allow for eventual scribing of the
architrave against an irregular plaster surface.
13.8.3 Corner T-junction
Figure 13.15: As illustrated in the plan-view details,
this type of junction receives similar treatment in its
three variations to those illustrated and described
before.
C
D
A
B
Figure 13.17 (a) Vertical sections
13.8.4 Doorway T-junction
Figure 13.16: As seen in these illustrations, similar
treatments apply in the same descending order.
Another consideration in this situation is to pack out
the lining (as shown), if necessary, to achieve full
width architraves each side.
Nogging
13.9 FLOOR AND CEILING
JUNCTIONS
Figure 13.17(a): Although stud partitions do not normally present weight problems on suspended timber
floors, certain points must be considered when a partition runs parallel to the joists and
●
●
rests on the floor boards either in a different position to a joist below as at A, or
rests in a position that coincides with a joist below,
as at B; (both situations inhibiting floor-board
removal for rewiring, etc.);
Figure 13.17 (b) Head-fixings
●
●
misses a joist required for head-plate fixings, C;
creates a problem in board-fixings on each side
of the head, if erected before the ceiling is boarded,
as at D.
Floor and Ceiling Junctions
13.9.1 Creating Head-fixings
191
13.9.3 Creating a Beam Effect
Figure 13.17(b): This shows a method of overcoming
the lack of head-fixings by inserting 100 ⫻ 50 mm (or
less) noggings between the ceiling joists at about 1 m
centres. Where there is access above the ceiling joists,
as in a loft, these noggings can be fixed before or after
the ceiling is boarded; however, where there is no
access above, as with floor joists that have been
floored, then obviously the noggings must go in before
the ceiling is boarded.
50
75
50
225
13.9.2 Double Ceiling-and-floor Joists
Figure 13.17 (e) Timber-connectors between joists
12 mm
gap
Figure 13.17(e): To achieve more of a beam effect with
the double floor-joists – and so offset the disadvantage
of a direct load – the support-blocks could be replaced
by a continuous middle-joist, bolted into position
with 12 mm diameter bolts, 50 mm round or square
washers and 75 mm diameter toothed timber connectors at maximum 900 mm centres.
13.9.4 Partition across Joists
Figure 13.17 (c) Double ceiling-and-floor joists
Figure 13.17(c): This shows a way of overcoming all
the previous issues, but uses more timber and requires
extra work and careful setting-out at the joisting stage.
Arrangements of double ceiling-and-floor joists, with
support-blocks between, are set up. The blocks should
be inserted at a maximum of 1 m centres and fixed
from each side with 100 mm round-head wire nails,
staggered as in Figure 13.17(d).
100 ⫻ 50 mm
ceiling
joists
12 mm
gap
225 ⫻ 50 mm
joists
Figure 13.17 (f) Partition at right-angles to joists
Figure 13.17 (d) Support-blocks
Figure 13.17( f ): This illustrates a situation that presents no problems, when the partition runs at rightangles to the floor and ceiling joists. The sill or floor
plate is best fixed on the joists, to allow for expansion
and contraction of the floor membrane – hence the
12 mm gap each side – but can be fixed on the flooring. Likewise, the head plate can either be fixed
directly to the joists or to the boarded ceiling.
192
Erecting Timber Stud Partitions
13.9.5 Fixing Boards for Skimming
Figure 13.18(a): Plasterboards come in a variety of
sizes, perhaps the most popular of these being
2.4 m ⫻ 1.2 m of 9.5 mm or 12.5 mm thickness. The
illustration shows boards of 9.5 mm thickness, laid on
edge, fixed to stud-spacings of 400 mm centres, in an
arrangement suitable for skimming with finishing
plaster, after reinforcing the joints with bandage or
hessian skrim. Boards are fixed with 30 mm galvanized clout nails, at approximately 150 mm centres.
within the indentation of the tapered edges, to achieve
a finish.
13.9.7 Spacing of Studs
Door stud
400
400
∗
∗ Starting point for stud-spacings
Figure 13.18 (c) Spacing of studs
Figure 13.18 (a) Fixing boards for skimming
Figure13.18(c): As illustrated, it must be noted that
the spacing of studs should start from the edge of the
door-stud, to the centre of the intermediate studs, to
achieve correct centres and full coverage of the doorstud edge by the board material.
13.9.8 Fixing Noggings
13.9.6 Fixing Boards for Dry Finish
Fix
Temporary
strut
Figure 13.18 (b) Fixing boards for dry finish
Figure 13.18(b): The illustration shows TE boards
(tapered-edge plasterboards) of 12.5 mm thickness,
laid on their ends to eliminate horizontal joints and
fixed to stud-spacings of 600 mm centres, using either
38 mm galvanized clout nails, at approximately
200 mm centres. Alternatively, bugle-head countersunk, sherardized screws of a similar length can be
used to achieve a countersunk hole for filling and to
reduce the risk of surface damage from hammerblows. Decorators usually attend to the nail or screw
holes and also fill, tape and refill the vertical joints
Remove
Figure 13.19 Alternative method of supporting noggings
during fixing
Figure 13.19: As shown here, a temporary strut of
100 ⫻ 50 mm section, with bevelled ends to
facilitate easy and quick removal, can be positioned
to support a nogging during fixing with skew-nails,
then lightly tapped at its base to remove it for the
next fixing.
14
Geometry for Arch Shapes
14.1 INTRODUCTION
Brick or stone arches over windows or doorways, in a
variety of geometrical shapes, can only now be seen
mainly on older-type buildings. Present-day design
favours straight lines for various reasons, including
visual simplicity, cost, and structural requirements in
relation to new materials and design. Curved arches in
domestic buildings have been replaced mostly by various types of light-weight, galvanized, pressed-steel
lintels as shown in Figure 14.1(a).
However, arches should not be regarded as oldfashioned or obsolete and will still be required to match
existing work on property maintenance, conversions and
extensions. Also, some architects nowadays are using
geometrical shapes in modern design.
Arches for internal doorways, to be finished in plaster, are quite popular and can be formed traditionally
with a structural brick-arch, although the modern practice is to use a lightweight, galvanized steel archformer,
which is easily fitted and fixed within a standard preformed doorway, ready for plastering.
Brick or stone arches are built on temporary
wooden structures called centres, dealt with in the
next chapter.
14.2 BASIC DEFINITIONS
Figure 14.1 (b):
●
●
●
●
●
●
●
●
Springing line: a horizontal reference or datum line
at the base of an arch (where the arch springs from).
Span: the distance between the reveals (sides) of the
opening.
Centre line: a vertical setting-out line equal to half
the span.
Rise: a measurement on the centre line between
springing and intrados.
Intrados or soffit: the underside of the arch.
Extrados: the topside of the arch.
Crown: the highest point on the extrados.
Voussoirs (pronounced vooswars): wedge-shaped
units in the arch.
Figure 14.1 (a) Modern steel lintels
194
Geometry for Arch Shapes
Voussoir
Key
Crown
Extrados
a r c
h
i c k
B r
Rise
Springing line
Intrados
or soffit
CL = Centre line
method used. Line AB has been bisected. Using A as
centre, set the compass to any distance greater than
half AB. Strike arcs AC1 and AD1. Now using B as
centre and the same compass setting, strike arcs BC2
and BD2. The arcs shown as broken lines are only
used to clarify the method of bisection and need not
normally be shown. Draw a line through the intersecting arcs C1 C2 to D1D2. This will cut AB at E into
two equal parts. Angles C1EA, BEC2, AED1 and
D2EB will also be right-angles (90⬚).
14.3.2 Bisecting an Angle
Span
C
Radius
D
Centre point
F
Figure 14.1 (b) Basic definitions
●
●
●
Key: the central voussoir at the crown (i.e. the final
insert that locks the arch structurally).
Centre: the pivoting or compass point of the radius.
Radius: the geometrical distance of the centre point
from the concave of a segment or circle.
A
E
B
Figure 14.2 (b) Bisecting an angle
Before proceeding, a few basic techniques in geometry
must be understood.
This means cutting or dividing the angle equally into
two angles. Figure 14.2(b) shows angle CAB. With A
as centre and any radius less than AC, strike arc DE.
With D and E as centres and a radius greater than half
DE, strike intersecting arcs at F. Join AF to divide the
angle CAB into equal parts, CAF and FAB.
14.3.1 Bisecting a Line
14.3.3 Semi-circular Arch
14.3 BASIC TECHNIQUES
This means dividing a line, or distance between two
points, equally into two parts by another line intersecting at right-angles. Figure 14.2(a) illustrates the
1
C
A
C
2
E
B
Figure 14.3 Semi-circular arch
1
D
D
2
Figure 14.2 (a) Bisecting a line
Figure 14.3: Span AB is bisected to give C on the springing line. With C as centre, describe the semicircle from
A to B.
Basic Techniques
14.3.4 Segmental Arch
195
Hyperbola
This is the name given to the curve A, produced when
a cone is cut by a plane (a flat, imaginary sheet-surface)
making a larger angle with the base than the side angle
of the cone (e.g. for a 60⬚ cone use a 70–90⬚ cut).
Parabola
This is the name given to the curve B, produced when
a cone is cut by a plane parallel to its side (e.g. for a
60⬚ cone use a 60⬚ cut).
Ellipse
This is the name given to the shape C, produced
when a cone or cylinder is cut by a plane making a
smaller angle with the base than the side angle of the
cone (or a cylinder). The exception is that when the
cutting plane is parallel to the base, true circles will
be produced.
Axes of the Ellipse
Figure 14.4 Segmental arch
ABCD = ellipse axes
ABC = semi-ellipse axes
C
axis
Figure 14.4: Span AB is bisected to give C. The rise
at D on the centre line can be at any distance from C,
but less than half the span. Bisect the imaginary
line AD to intersect with the centre line at E. With
E as centre, describe the segment from A, through
D to B.
14.3.5 Definition of Geometrical
Shapes
Major
axis
E
B
Minor
A
D
A
B
C
AE or EB = semi-major axis
CE or ED = semi-minor axis
Figure 14.5 (b) Axes of the ellipse
C
A
Hyperbola
B
Parabola
Ellipse
Figure 14.5 (a) Definition of geometrical shapes
Illustrated in Figure 14.5(a) is an explanation for some
of the other arch shapes to follow.
Figure 14.5(b): An imaginary line through the base
and top of a cone or cylinder, that cuts exactly through
the centre, is known as an axis. The shape around the
axis (centre) is equal in any direction, but when cut by
an angled plane – to form an ellipse – the shape
enlarges in one direction, according to the angle of
cut. For reference, the long and the short lines that
intersect through the centre, are called the major axis
and the minor axis.
The axes on each side of the central intersection, by
virtue of being halved, are called semi-major and
196
Geometry for Arch Shapes
200 mm
Normal
300 mm
90°
70
Tangent
70
6 mm plywood
18 mm panel pins,
touching top of wooden centre
at any position, gives correct line
of voussoirs on blade of template
(a)
semi-minor axes. The semi-elliptical arch is so called
because only half of the ellipse is used.
14.4 TRUE SEMI-ELLIPTICAL
ARCHES
True semi-elliptical shapes are not normally used
for brick arches, as the methods of setting out do not
give the bricklayer the necessary centre points as a reference to the radiating geometrical-normals of the
voussoir joints. However, the problem could be solved
by using a simple, purpose-made tangent-template,
as shown in Figure 14.6(a). Therefore, the true semielliptical arch methods shown here might only serve
to build a complete knowledge of the subject being
covered, leading on to the methods favoured by
bricklayers.
C
A
2
3
4
5
5
4
3
O
Q
6
S
T
C
6
M
6
7
8
7
1
8
1
9
1
10
1
11
1
12
9 10 11 12
E
B
D
Figure 14.6 (b) Intersecting-lines method
Figure 14.6(b): Span AB, given as the major axis, is
bisected at E to produce CD, a lesser amount than
AB, given as the minor axis. Vertical lines from AB
R
5
4
P
3
N
2
K
L
1
H
2
J
Ø
F
1
3 4 5 6
E
G
1
1
14.4.2 Intersecting-arcs Method
A
1
6
1
5
1
4
1
3
1
2
1
1
and horizontal lines from C are drawn to form the
rectangle AFGB. Lines AF, GB, AE and EB are
divided by an equal, convenient number of parts.
Radiating lines are drawn from C to 11, 21, 31, and so
on to 121; and from D, through divisions 1 to 12 on
the major axis, to intersect with their corresponding
radial. These are radials 1 to 11, 2 to 21, 3 to 31, and so
on. The intersections plot the path of the semi-ellipse
to be drawn freehand or by other means, such as with
the aid of a flexi-curve instrument.
12
14.4.1 Intersecting-lines Method
F
Figure 14.6 (a) Tangent-template
Ø
G
B
Figure 14.7 Intersecting-arcs method
Figure 14.7: Draw the major axis AB and the semiminor axis CE as before. With compass set to AE or
EB, and C as centre, strike arcs F and G on the major
axis; these are known as the focal points. Mark a number of points anywhere on the semi-major axis
between F and E; place the first point very close to F.
Number these points 1,2,3, etc. Now with the compass set to A1, strike arcs H1 from F, and J1 from G.
Reset compass to B1, strike arcs H1 from G, and J1
from F. Continue as follows:
compass A2, strike K2 from F, L2 from G
compass B2, strike K2 from G, L2 from F
compass A3, strike M3 from F, N3 from G
compass B3, strike M3 from G, N3 from F
compass A4, strike O4 from F, P4 from G
True Semi-elliptical Arches
197
axis A1E1 and the semi-minor axis C1E2. Rotate the
trammel in a variety of positions similar to that
shown, ensuring that marks E1 and E2 always touch
the two axes, and mark off sufficient points at A1/C1
to plot the path of the semi-ellipse to be completed
as before.
compass B4, strike O4 from G, P4 from F
compass A5, strike Q5 from F, R5 from G
compass B5, strike Q5 from G, R5 from F
compass A6, strike S6 from F, T6 from G
compass B6, strike S6 from G, T6 from F
These arcs plot the path of the semi-ellipse to be
completed as before.
14.4.5 Long-trammel Method
14.4.3 Concentric-circles Method
5
6
4
C
7
3
8
2
14
15
C
16
A
18
12
10
19
11
20
A
E
Trammel
= EC
O
9
17
13
1
= AE
E
B
Figure 14.10 Long-trammel method
B
Figure 14.8 Concentric-circles method
Figure 14.8: Draw the major axis AB and the semiminor axis CE as before. Strike semi-circles radius EA
and EC. Draw any number of radiating lines from E to
cut both semi-circles. For convenience, the angles of the
radials used here are 15⬚, 30⬚, 45⬚, 60⬚ and 75⬚, each side
of the centre line CE. Draw vertical lines inwards from
points 1, 2, 3, etc. on the outer semi-circle, and horizontal lines outwards from points 11, 12, 13, etc. on the
inner semi-circle. These intersect at points ⬚, which
plot the path of the semi-ellipse to be completed as
before.
Figure 14.10: This is similar to the previous method,
except that the semi-major and semi-minor axes
form a continuous measurement on the trammel rod;
the outer marks thereon move along the axes, while
the inner mark, O, plots the path of the semi-ellipse.
This method is better than the previous one when
the difference in length between the two axes is
only slight.
14.4.6 Pin-and-string Method
J
C
H
C
I
1
Pencil jig
14.4.4 Short-trammel Method
A
C
E
G
B
Plan
Figure 14.11 Pin-and-string method
Trammel
= CE
= AE
A
F
E
1
A
1
C
1
B
E
2
E
Figure 14.9 Short-trammel method
Figure 14.9: Draw the major and semi-minor axes as
before. Select a thin lath or strip of hardboard, etc., as
a trammel rod. Mark it as shown, with the semi-major
Figure 14.11: This method uses focal points on
the major axis. These are shown here as F and G,
and either point equals AE or EB on the compass,
struck from C to give F and G. This time, to describe
the arch shape, drive nails into points F, C and G,
pass a piece of string around the three nails and
tie tightly. Make a pencil jig, if possible, and cut a
notch in a pencil – as shown at C1 – remove nail
at C, replace with pencil and jig and rotate to left
and right, as indicated at HIJ, to produce a true
semi-ellipse.
198
Geometry for Arch Shapes
14.5 APPROXIMATE SEMIELLIPTICAL ARCHES
14.5.2 Five-centred Method
These approximate semi-elliptical shapes, as previously
mentioned, are preferred for brick or stone arches, as they
eliminate the freehand flexi-curve, simplify the setting
out and give the bricklayer definite centre points from
which to strike lines for the radiating geometricalnormals of the voussoir joints.
C
F
P
H
2
G
1
R
L
K
A
1
E
2
J
14.5.1 Three-centred Method
B
M
F
N
I
D
C
K
G
Figure 14.13 Five-centred method
L
H
J
A
E
B
I
Figure 14.12 Three-centred method
Figure 14.12: Draw major axis (span) and semi-minor
axis (rise) to the sizes required, as described before.
Draw a diagonal line from A to C (the chosen or
given rise). With centre E, describe semi-circle AB to
give F. With centre C, strike an arc from F to give G.
Bisect AG to give centres H and I. With centre E,
transfer H to give J. Draw the line through IJ to give
L. HIJ are the three centres. Draw segments AK from
H, BL from J, and KL from I, to cut through the rise
at C and complete the required shape.
Figure 14.13: Draw major and semi-minor axes as
before. Draw lines AF and CF, equal to CE and AE,
respectively. Divide AF by three, to give A12F. Draw
radials C1 and C2. With centre E and radius EC,
strike the arc at D on the centre line. Divide AE by
three, to give A12E. Draw line D1 to strike C1 at G,
and line D2 to strike C2 at H. Bisect HC and extend
the bisecting line down to give I on the centre line.
Draw a line from H to I. Now bisect GH and extend
the bisecting line down to cut the springing line at K
and line HI at J. IJK are the three centres to form half
of the semi-ellipse. The other two centres are transferred as follows: with centre E, transfer K to give L
on the springing line; draw a horizontal line from J to
M and beyond; with centre M, strike an arc from J to
give the centre N. To transfer the normals G and H,
strike arc CP, equal to CH, and BR, equal to AG. To
form the semi-ellipse, draw segments AG from centre
K, GH from J, HCP from I, PR from N, and RB
from L.
F
To G
C
cL
K
H
A
Figure 14.14 Depressed semi-elliptical arch
I
L
G
J
E
B
Tudor Arches
14.5.3 Depressed Semi-elliptical Arch
Figure 14.14: This arch uses a very small rise. The
geometry is exactly the same as that used for the
three-centred method explained in Figure 14.12.
14.6 GOTHIC ARCHES
this arch come within the span, on the springing line.
Bisect the span AB to give the centre line through E.
With compass less than AB, strike the rise at C from A.
Alternatively, mark the chosen or given rise at C from
E. Draw line AC and bisect to give centre F on the
springing line. With centre E, transfer F to give centre
G. Strike segments AC from F and BC from G.
14.6.3 Lancet Gothic Arch
14.6.1 Equilateral Gothic Arch
C
Tangent
C
199
D
90°
L
K
J
Normal
I
H
G
G
F
E
F
A
A
E
B
B
Figure 14.17 Lancet Gothic arch
Figure 14.15 Equilateral Gothic arch
Figure 14.15: The radius of this arch, equal to the
span, is struck from centres A and B to a point C. The
line AD highlights a geometrical normal to the curve
and a line at right-angles to this, as shown, is known
as a tangent. Normals E, F, G, H, I, J, K, L, etc. are
indicated by broken lines to form the voussoirs of the
arch. Incidentally, points A, B and C of this arch, if
joined by lines instead of curved arcs, form an equilateral triangle, where all three sides are equal in length
and contain three angles of 60⬚.
Figure 14.17: The centres for this type of arch are outside the span, on an extended springing line. Bisect
the span AB to give the centre line through E. With
compass more than AB, strike the rise at C from A.
Alternatively, mark the chosen or given rise at C from
E. Draw line AC and bisect to give centre F on the
extended springing line. With centre E, transfer F to
give centre G. Strike segments AC from F and BC
from G.
Note that line AC in the above is optional and
need not actually be drawn.
14.6.2 Depressed Gothic Arch
Figure 14.16: This arch is sometimes referred to as an
obtuse or drop Gothic arch. The centres for striking
14.7.1 Tudor Arch – Variable Method
C
G
A
F
E
Figure 14.16 Depressed Gothic arch
14.7 TUDOR ARCHES
B
Figure 14.18: This method is best and can be used to
meet a variety of given or chosen rises. The geometry
is usually mastered when practised a few times.
Draw the span AB and bisect it to give an extended
centre line through E and down. Mark the rise at C.
Draw vertical line AF, equal to two-thirds rise (CE).
Join F to C. At right-angles to FC, draw a line down
from C. With compass equal to AF, and A as centre,
transfer F to give G. With the same compass setting,
mark H from C on line CI. Draw line from G to H
and bisect; extend bisecting line down until it intersects with line CI to give centre I. Draw line from I,
200
Geometry for Arch Shapes
C
F
90°
M
H
A
G
E
N
J
B
Figure 14.19: This method is simpler and can be used
when the rise is not critical and the only information
given or known is the span.
Draw span AB and divide by four to give DEF.
Draw vertical lines down from D and F. With D as
centre, transfer F to intersect the vertical line, giving
G. With F as centre, transfer D to intersect the other
vertical line, giving H. Draw diagonals from H and G,
extending through D and F on the springing line. To
complete, strike segments AI from D, IC from H, BJ
from F and JC from G.
14.7.3 Depressed Tudor Arch
C
I
L
A
I
K
J
D
E
F
G
H
B
Figure 14.18 Tudor arch – variable method
extended through G on the springing line. With E as
centre, transfer G to give J on the springing line.
Again with E as centre, transfer I, through K, to strike
arc at L. With K as centre, transfer I to give centre L.
Draw line from L to extend through J on the springing line. To complete, strike segments AM from G,
MC from I, CN from L and NB from J.
O
K
14.7.2 Tudor Arch – Fixed Method
Figure 14.20 Depressed Tudor arch
C
J
I
A
D
E
G
Figure 14.19 Tudor arch – fixed method
F
H
L
B
Figure 14.20: Draw span AB and divide by six to give
DEFGH. Draw vertical lines down from E and G. With
centre D, transfer H down to O, and with centre H,
transfer D down to O. Draw diagonal normals through
DO and HO, extending down to intersect the vertical
lines at K and L, and extending up past the springing
line to I and J. To complete the arch, strike segments
AI from D, IC from L, BJ from H and JC from K.
Note that division of the span can be varied to
achieve a different visual effect, as can the angles of the
normals at D and H, drawn here at 60⬚. For example,
75⬚ would make the arch more depressed.
14.7.4 Straight-top Tudor Arch
Figure 14.21: Draw span AB and divide by 9. Mark
one-ninth of span from A to give D, and one-ninth
Hyperbolic Arch
C
90°
F
A
D
90°
78°
78°
G
E
B
201
Figure 14.22: Draw AB equal to the span, and vertical
height EC equal to twice the rise. Join AC and CB
to form a triangle. Divide each side of the triangle by
a convenient number of equal divisions. This illustration uses seven divisions each side, numbered A, 1, 2,
3, 4, 5, 6, C, and C, 1, 2, 3, 4, 5, 6, B. Join 1 on AC
to 1 on CB, 2 on AC to 2 on CB, and so on. These
lines are tangential to the curve and give the outline
shape of the parabola to be drawn freehand or by
other means.
14.8.2 Intersecting-lines Method
C
Figure 14.21 Straight-top Tudor arch
14.8 PARABOLIC ARCHES
14.8.1 Triangle Method
C
2
2
3
3
4
4
A
4
3
2
1
O
1
2
3
4
B
Figure 14.23 Parabolic arch – intersecting lines method
Figure 14.23: Draw a rectangle ABDC in which AB
equals the span and AC equals the rise. Bisect AB to
give vertical line EO. Divide OA into any number of
equal parts, and OB, CA and DB, into the same number of equal parts as OA. Draw vertical lines up from
horizontal divisions, and radiating lines from E to vertical divisions. The intersections thus formed, being
base-vertical 1 (bv1) intersecting side-radial 1 (sr1),
bv2 intersecting sr2, etc., on each side of the centre
line, gives the outline shape of the parabola, to be
completed as before.
14.9 HYPERBOLIC ARCH
2
4
3
D
14.9.1 Intersecting-lines Method
4
2
5
1
A
1
1
5
3
E
1
from B to give E. With a protractor, or a roofingsquare containing a degree facility, set up diagonal
normals passing through D and E at 78⬚ to the horizontal. With centre D, strike arch curve AF, and with
centre E, strike BG. From F and G, draw straight
crown lines at 90⬚ to the two normals, to intersect at
key-position C.
Note that positions of the centres D and E can be
varied to achieve a different visual effect, as can the
angles of the normals at D and E, drawn here at 78⬚;
however, the arch top or crown must always be tangential (at 90⬚) to the normals.
6
D
6
E
Figure 14.22 Parabolic arch – triangle method
B
Figure 14.24: As before, draw a rectangle ABDC
in which AB equals the span and AC equals the
rise. Bisect AB to give vertical line EFO. Make
apex E from F equal to half the rise (EF ⫽ FO/2).
Divide OA, OB, CA and DB, as before and draw
intersecting radials thus: base-radial 1 (br1) intersecting side-radial 1 (sr1), br2 intersecting sr2, etc., on
each side of the centre line. The intersections give
the outline shape of the hyperbola, to be completed
as before.
202
Geometry for Arch Shapes
Note that, as with true semi-elliptical shapes (Figures
14.6 to 14.11), parabolic and hyperbolic arches, if constructed of brick or stone, requiring centres and normals
for alignment of joints, present the same problems. To
overcome this, the tangent-template (see Figure 14.6(a))
could be used.
E
C
D
EF
1
1
2
2
3
3
4
4
A
4
3
2
1
O
Figure 14.24 Hyperbolic arch
1
2
3
4
B
15
Making and Fixing
Arch Centres
15.1 INTRODUCTION
The temporary wooden structures upon which brick
arches are formed, are known as centres. They can be
made in the joinery shop – taking advantage of a
greater variety of machinery – or on site. The construction of the centre can be simple or complex,
depending mainly on two factors: the span of the
opening, and how many times the centre is to be used
for other arch constructions.
15.1.1 Simple or Complex
For small spans up to about 1.2 m, the centre can be
simple, of single-rib, twin-rib or four-rib construction.
For spans exceeding 1.2 m, the centre becomes more
complex, of multi-rib construction.
a radius rod can be easily made, consisting of a timber
lath with a panel pin or nail through one end, the other
end drilled to hold a pencil firmly.
15.2 SOLID TURNING PIECE
(SINGLE-RIB)
Folding wedges
100 ⫻ 50 mm props
Figure 15.2 (a) Turning piece
15.1.2 Practical Compass
Trammel heads
Pencil
Beam
Beam compass
Pencil
Eccentric point
(turn for fine adjustment
of radius)
Panel pin or nail
Radius rod
Figure 15.1 Radius rod and beam compass
Figure 15.1: A beam compass or a radius rod is required
to set out the full-size shape of the centre, either
directly onto the rib material (single and twin-rib) or
onto a hardboard or similar setting-out board (four-rib
and multi-rib centres), from which a template is made
of the common rib shape. The beam compass consists
of a pair of trammel heads and a length of timber, say of
38 ⫻ 19 mm section, known as a beam. To improvise,
Figure 15.2(a): Solid turning pieces are used for segmental arches with small rises up to about 75 mm. If
the rise is too slight (say 10 mm rise, 900 mm span),
then a beam compass or radius rod would not be practical for drawing the curve and a triangular trammel
frame or trammel rod should be used. As illustrated in
Figure 15.2(b), to make the trammel rod or frame,
mark the required span AB and rise CD on the rib
material, place a board against CB and mark and cut
line A1C1. As shown separately, make a sawcut at C1 to
take a pencil. To mark semi-segment CA, position pencil at C1 and push the trammel against the protruding
nails at A and B, moving to the left. Reverse the trammel and move to the right to mark semi-segment CB.
15.2.1 Cutting the Segment
Figure 15.2(c): Ideally, the curve for the solid turningpiece is best cut with a narrow band-saw machine, or,
if on site, with a jigsaw. Alternatively, as shown in
204
Making and Fixing Arch Centres
Protruding nails
Rib
A
A
C
C1
D
1
Pencil
Sawcut at C1
to take pencil
B
C1
Triangular trammel rod
A
C
Rib
B
Figure 15.2 (b) Triangular trammel
rod and frame
Triangular trammel frame
Rib
Figure 15.2 (c) Tangential cuts
Figure 15.2(c), a series of tangential cuts can be made
with a circular saw or handsaw, prior to shaping with a
Surform and/or a traditional plane.
Figure 15.3 (b) Setting out
15.3 SINGLE-RIB CENTRES
15.3.2 Adding Springing Blocks
Semi-circular
High-rise segmental
Semi-elliptical
12 or 18 mm
plywood rib
Figure 15.3 (a) Single-rib centres
Figure 15.3(a): These centres follow an unconventional method of construction, but are surprisingly
strong and effective. Their strength is dependent upon
the stress of compression achieved in bending the
hardboard or plywood skin over the curved rib. For
this reason, they are more suitable for semi-circular,
high-rise segmental and semi-elliptical centres – in
that order of diminishing suitability – and less suitable
for Gothic, Tudor and low-rise segmental centres.
15.3.1 Marking and Cutting the Rib
Figure 15.3(b): The plywood rib, preferably of 18 mm
thickness, is set out along the springing line to the
span, minus the skin thickness each side, and marked
with a radius rod (or beam compass), as shown. The
shape is best cut – as before – by band saw or portable
jigsaw, but, if not available, the job can be done by
using a sharp compass saw, finishing with a flat spokeshave, Surform and/or a smoothing plane.
Wall thickness
less18 mm
Figure 15.3 (c) Adding springing blocks
Figures 15.3(c)–(e): Two 50 ⫻ 50 mm blocks, cut in
length to the brick size of the arch minus, say, 18 mm
inset-tolerance, are half-housed centrally to fit housings cut into the springing points of the rib on each
side and fixed with 63 mm oval, lost-head nails or
countersunk screws (Figures 15.3(c) and (d)). The
skin, of 3.5–4 mm hardboard or plywood, long enough
to cover the curved shape of the rib and as wide as the
block-length, must have the rib thickness pencilgauged through the centre (Figure 15.3(e)).
Twin-Rib Centres
205
material like chipboard or Sterling board, if the arch is
not being reused too many times. Bearers, of
75 ⫻ 25 mm or 100 ⫻ 25 mm section, are fixed to the
underside of the centre, at each end of the springing
line. These act as spacers between the two ribs and as
bearers supporting the centre on the props.
15.4.1 Bracing-spacers
Figure 15.3 (d) Springing blocks in place
Bracingspacer
15.3.3 Fixing the Skin
Bearer
Figure 15.4 (b) Bracing-spacer board
(f)
Direction of
grain, if
ply is
used
Hardboard
or plywood
skin
Figure 15.3 (e) Skin (f) Skin in place
Figure 15.3(f ): When finally fixing the skin to the
springing blocks and the rib, using 25 mm panel pins
or 32 mm small-headed clout nails, it is important to
ensure that the skin is taut and is centred on the rib,
following the gauge lines, as indicated. Note that the
length of skin can be calculated, or measured directly
from the rib shape by encircling the finished curve
with a tape rule.
Figure 15.4(b): A bracing-spacer board, equal to the
inside width of the centre, as indicated, can be inserted
to keep the ribs initially parallel and square. The centre
is then covered with a hardboard or plywood skin or,
alternatively, with strips of timber known as laggings,
illustrated in Figures 15.4(c) and 15.4(d). These can be
placed close together, referred to as close lagging, or be
spaced apart and referred to as open lagging, as indicated
in Figures 15.4(d) and (e). Close lagging should be used
25
16
Lagging on edge
as spacer when 18
32
fixing
16
Figure 15.4 (c) Lagging sizes for small spans
15.4 TWIN-RIB CENTRES
Figure 15.4(a): These centres are superior to the singlerib type and are suitable for all arch shapes. The ribs
may consist of 12–18 mm plywood – or other sheet
Ply-skin lagging
Open lagging
Figure 15.4 (a) Twin-rib centres
18
Close lagging
Figure 15.4 (d) Open and close lagging
206
Making and Fixing Arch Centres
Tenon-saw cut
Lagging
Nail
strip
Figure 15.4 (g) Lagging jig
Figure 15.4 (e) Centre with open lagging
for gauged arches with tapered bricks (voussoirs), and
open lagging for common arches with ordinary bricks
used as parallel voussoirs.
sawdust being pushed along from the right; the saw at
the other end cuts the required length repeatedly after
feeding in the strip towards the nail.
15.5 FOUR-RIB CENTRES
15.4.2 Making the Centre
Segmental
Semi-elliptical
Gothic
Tudor
Figure 15.5 (a) Four-rib centres
Hardboard or
ply skin
Figure 15.4 (f) Applying the skin
Figure 15.4( f ): To make the centre, set out and form
one rib as previously described. Use the first rib as a
template to mark out and form the second rib. Cut the
two 75 ⫻ 25 mm bearers in length to the brick size of
the arch, minus 18 mm inset-tolerance, and fix to the
underside of the ribs at each end with minimum
50 mm round-head or lost-head wire nails. Cut and
fix the bracing-spacer (Figure 15.4(b)). Cut the hardboard or plywood skin to width (equal to length of
bearers) and fix to the ribs, as indicated in Figure
15.4(f ), or cut the laggings and fix to the ribs with 38
or 50 mm lost-head oval nails.
15.4.3 Lagging Jig
Figure 15.4(g): This shows a plan view of a simple jig
for cutting the lengths of lagging quickly. Two
50 ⫻ 25 mm battens are fixed to a bench, stool top or
scaffold board, to form the jig. As indicated, a nail at
one end positions the lagging strip without trapping
Figure 15.5(a): These centres follow traditional methods
of construction and are suitable for all arch shapes
except low rise, which require only one or two ribs for
small spans, as shown previously in Figures 15.2(a)
and 15.4(e). Because of the time involved in making
four-rib centres, they are less favoured than twin-rib
centres using sheet material. As seen in elevation and
section A–A in Figure 15.5(b), four ribs are required,
two tie beams, two collars, two bearers, two optional
struts, an optional brace and laggings.
15.5.1 Construction Details
Figures 15.5(b) and (c): Each pair of ribs is connected
to a top collar and a bottom tie beam by clench-nails.
Rib
seat
cut
A
Rib
Rib
plumb
cut
Rib
Collar
or
Tie
Elevation
A
Section A–A
Bearer
Optional strut
Figure 15.5 (b) Semi-circular centre
Optional brace
Four-Rib Centres
Figure 15.5 (c) Staggered clench-nailing
As indicated in Figure 15.5(c), when driven in, the
nails purposely protrude by at least 6 mm and are then
bent sideways and clenched over to secure the joint.
For extra strength, optional struts can be fixed from the
birdsmouth at the apex of the ribs, against the collar, to
a central position on the face of the lower tie. The two
bearers are fixed to the ends of the lower ties to line up
the rib structures and act as bearers, supporting the
centre when resting on the props and wedges.
(this reduction is a practical tolerance to allow for
brick reveals being slightly out of square or irregular).
Next, bisect line AB to produce the centre line CD.
Then set the beam compass or radius rod to AD and
describe the semi-circle ACB. Reset the compass or
radius rod to AD minus the lagging thickness and
describe the second semi-circle, producing A1, C1, and
B1, representing the rib curve. Now measure down at
least 60 mm from C1 to G, as the depth of the rib’s
plumb cut and measure inwards at least 60 mm from
A1 to E, and B1 to F, being the length of the rib’s seat
cuts. Draw tangential lines EG and GF, representing
the underside of the ribs. Draw two lines parallel
to the springing, representing the top collar and
bottom tie beam; these timbers should be about
100–150 mm wide ⫻ 25 mm thickness.
15.5.4 Marking and Cutting the Ribs
1
Hardboard or plywood skins can be used to cover the
centre, in single or double thicknesses – or traditional
laggings can be used, efficiently cut to length as previously described and fixed to the curved ribs, as before
with 38 or 50 mm lost-head oval nails.
Note that, if considered necessary, an optional
brace, indicated in section A–A of Figure 15.5(b), can
be used to achieve squareness in width and greater
rigidity between the two rib structures.
15.5.3 Setting Out
1
3
2
150 ⫻ 25 mm boards
2
15.5.2 Optional Skins
207
4
3
or
4
1
2
225 ⫻ 25 mm board
Figure 15.5 (e) Method of marking out ribs
Waste area
Figure 15.5 (f) Producing a hardboard template
Hardboard offcut
C
1
C
G
1
1
B
A
A
E
D
F B
Figure 15.5 (d) Setting-out board
Figure 15.5(d): To produce the rib shape for this type
of arch and also to ensure that the finished centre is
true to shape, a setting-out board is required. The
figure indicates the setting out for a semi-circular
centre. The first line to be drawn is line AB on the
springing line, representing the span minus 2–3 mm
Figures 15.5(e) and ( f ): The rib segments can be cut
from a 150 ⫻ 25 mm or 225 ⫻ 25 mm board, as illustrated. A hardboard template, shown in Figure
15.5(f ), facilitates the marking out of the ribs onto the
board economically. To make the template, lay a piece
of hardboard on the setting-out board, as shown by
the dotted outline in Figure 15.5(d), strike the compass or rod from centre D to describe the quadrant
A1C1, mark the plumb cut CG and the seat cut AE,
then remove and cut to shape.
15.5.5 Marking the Collar and Tie
Figure 15.5(g ): The collar and tie are laid in position
on the setting-out board and marked with the compass or radius rod setting of A1D, struck from centre
D1, squared up from D. As shown, a small temporary
wooden block can be fixed to the tie, to retain the
point of the radius rod or compass.
208
Making and Fixing Arch Centres
15.6.1 Semi-hexagonal Configuration
Collar
1
D
D
1
D
Tie
Figure 15.5 (g) Marking out collar and tie
Figure 15.6(a): An elevation and sectional view of a
semi-circular centre suitable for spans up to about 4 m
are illustrated. The joints of each rib radiate from the
centre point, comprising six sector-shapes with angles
of 30⬚ (6 ⫻ 30⬚ ⫽ 180⬚). Given joint-lengths of about
60 mm, it follows that the underside of the ribs is tangential to the curve and forms two semi-hexagonal
shapes. This is seen more clearly in Figure 15.6(b).
For extra strength, struts should be added as shown.
15.6.2 Semi-octagonal Configuration
15.6 MULTI-RIB CENTRES
These centres also follow traditional methods of construction, simply because their multi-rib design allows
a variety of configurations suitable for very wide archspans. They are mainly used for high-rise segmental,
semi-circular and semi-elliptical arches. According to
the span, they may have to be set out directly on the
floor, or onto two or more setting-out boards placed
side by side. The principles of setting out and producing rib templates are similar to those described for
four-rib centres.
Figure 15.7(a): An elevation and sectional view of a
semi-elliptical centre are shown (drawn by a three-centre
method), suitable – as before – for spans up to about 4 m.
The joint-lines radiate from the centre point, comprising
eight sector shapes with angles of 22-21⬚ (8 ⫻ 22-21⬚ ⫽
180⬚). (Alternatively, the joints and struts can radiate
from the three centres of the semi-ellipse.) Measuring
equal amounts of about 60 mm along each joint-line, to
determine the line of the ribs, the underside of the ribs
forms two distorted semi-octagonal shapes; true octagonal shapes occur with semi-circular centres, as seen
more clearly in Figure 15.7(b).
ex. 225 ⫻ 25 mm
ribs
Brace
150 ⫻ 25 mm
struts
225 ⫻ 25 mm tie
(a)
Section
(b)
Figure 15.6 (a) Multi-rib semi-circular centre (b) Semi-hexagons
Brace
225 ⫻ 25 mm tie
Prop
Wedges
(a)
Figure 15.7 (a) Multi-rib semi-elliptical centre (b) Semi-octagons
Section
(b)
Multi-Rib Centres
15.6.3 Props and Folding Wedges
Props are required to give support to the arch centre
and its temporary load. The timber sizes and arrangements of these props will vary according to the size of
the centre and arch to be supported. Folding wedges,
under each end of the arch-centre and on top of the
props, are required for three reasons. First, they can be
adjusted to help set the centre’s springing line and
height to the correct level. Second, soon after the arch
has been ‘locked’ by the insertion of the final key brick
or voussoir – and without being left overnight – the
wedges are very gently eased to drop the centre by
about 3–4 mm, allowing the arch to settle without
cracking. Third, when the centre is finally being
removed, further easing and removal of the wedges
will make the job easier and less hazardous.
209
100 ⫻ 50
bearers
Gusset
Props
Brace
Strut
Sole
plate
Single prop
Double prop
Figure 15.8 (b) Props for large centres
15.6.4 Prop Arrangements
15.6.5 Wedge Shapes and
Lagging Sizes
50 to 75
38 ⫻ 250 cleat
200 mm
Strut
15
35
15
35
Figure 15.8 (a) Prop for small centres
Slow-driving wedges
Figure 15.8(a): An unconventional but effective
method of temporary support for small centres is
shown. Short-lengths of timber cleats are fixed on
each reveal of the opening, nailed with heads protruding and strutted as shown. The strut is vital to this
arrangement. Figure 15.8(b) shows a slightly modified
traditional method, using 100 ⫻ 50 mm single props
each side, with plywood gussets and 100 ⫻ 50 mm
bearers – and another method is shown using
double props each side. Both of these methods are
for large spans and each should have some form of
strutting.
Fast-driving wedges
Figure 15.8 (c) Folding wedges
Figure 15.8(c): Folding wedges, as illustrated, should
be ‘slow-driving’ (be cut with a shallow angle), as these
are better for fine adjustments, non-slip bearing, and
easing (slackening) prior to striking (removing) the
centre. Lagging sizes for large centres are usually
25 ⫻ 38 mm or 25 ⫻ 50 mm.
16
Fixing Architraves, Skirting,
Dado and Picture Rails
16.1 ARCHITRAVES
Figure 16.1(a): This is the name still used to describe
the cover moulds of various designs and sizes that are
fixed around the edges of door linings and door frames,
etc., primarily to cover the joint between the lining or
frame within the opening and the plaster (or plasterboard) surface of the wall. Even though present-day
architraves are usually plain in design, architraves also
add a visual finish to the opening. They are referred to
as being in sets. A set of architraves for a door opening
consists of two uprights, called jambs or legs and a
horizontal piece called a head. A door lining or frame
normally requires two sets of architraves, one on each
side of the wall.
16.1.1 Number of Sets Required
On a second-fixing operation, the architraves need to
be fixed before the skirting, so that the skirting on each
side of a doorway can be butted up against the back of
Head
Leg
16.1.2 Margins
Figure 16.1(b): The architraves are always set back from
the edge by a small amount, referred to as a margin. The
margin is usually either 6 mm or 9 mm and whatever
amount is decided upon or required, it must be consistently maintained around the opening. Inconsistent
margins, often varying in size between the legs and the
head and tapering from, say, 6 mm to 3 mm, are too
often seen and reflect a very low standard of workmanship, spoiling the appearance of the finished job. The
best way to establish a consistent margin, is to mark the
required amount around the lining or frame’s edge with
a sharp pencil. It need not be a continuous line; broken
lines of about 50–150 mm length, marked at about
Architrave
Leg
A
the architrave leg. To do the job efficiently, count the
number of doorways in the dwelling and cut all of the
sets required in one operation. For example, if there are
five doorways, then ten sets of architraves are required,
which is 10 heads and 20 legs. These are initially cut
up squarely by chop saw, with an allowance in length
for mitring. The length of the legs will be the dooropening height plus the width of the architrave-head
plus about 30 mm allowance. The length of the heads
will be the door-opening width plus the width of the
architrave-leg each side plus about 40 mm allowance.
Some of this allowance is required for the margins.
A
Margin
Figure 16.1 (a) Elevation of a set of architraves
Figure 16.1 (b) Section A–A
Architraves
450 mm intervals will be enough to achieve a good margin, even if the architrave leg is ‘sprung’ out of shape.
16.1.3 Margin-template
9 mm margin
m
211
the other corner and marked. On each side jamb, the
template is held vertically against the head and marked
(to create the intersection), then slid down to mark the
mid-area, the bottom and intermediate positions
between these three, making five marks on each side and
three on the head. This method of marking should take
no more than one minute per set of architraves.
0m
15
16.1.4 Mitring and Fixing Technique
45 ⫻ 120 mm
60 mm
Figure 16.2 (a) Shouldered margin-template
A
B
Figure 16.3 Ill-fitting mitres
Margin
template
Figure 16.2 (b) Use of the margin-template
Figures 16.2(a) and (b): Measuring and marking these
margin lines would be tedious and time-consuming, so
they need to be gauged and this is best done with a shouldered margin-template. This can be made quite easily by
nailing two pieces of timber together, as illustrated, with
a 6 mm margin on one side and an alternative 9 mm
margin on the other. The ends are also shouldered to
allow the template to over-run when marking against
each top corner. These over-running marks (Figure
16.2(b)) create an overlapping intersection for marking
the leg and head mitres accurately. Holding the template
with one hand, the pencil in the other, the template is
held horizontally against the head and the corner and
marked, then slid to the mid-area and marked, then to
Figure 16.3: Next, two sets of architraves can be placed
near each doorway, ready for mitring and fixing. Starting
with the first set, stand each leg in position (one at a
time) and mark the inner point of the mitre from the
margin-intersection point, onto the inner edge of each
leg. These mitres are then cut on the waste side of the
mark by chop saw and, without the need for marking,
the left-hand mitre of the head is also cut. Next, the
left-hand leg is fixed carefully to the margin marks, at
top, bottom and centre positions, with three nails only,
their heads left protruding. The left-hand mitred head is
then tried in position. If the mitre is a good fit, then the
head is held firmly while the right-hand mitre is marked
at the intersection and then cut carefully. The righthand leg is then fixed, again with three nails only, their
heads left protruding. Next, the head is placed in position and the mitres are checked. If the appearance is as
at A, then the head-mitres need easing with a plane, if
as at B, then the leg-mitres need easing, which means
releasing the provisionally nailed leg(s).
16.1.5 Final Fixing
If the mitres are a good fit, then the head can be fixed
with three or four nails, 50–60 mm from the mitrepoint at each end and one or two between. Also, the
nailing of the legs can be completed with two more
nails between the spacings of the nails already used,
making seven nails in all on each leg, about 50–60 mm
up the leg and the same distance from the mitre-point,
212
Fixing Architraves, Skirting, Dado and Picture Rails
then spaced approximately 300 mm apart. The nails
used throughout are 38 mm oval nails, preferably the
lost-head type, which are easier for punching in. The
mitres are sometimes nailed through the top or side
edge to achieve flushness on the face side and to close
and hold the mitre. These mitre-fixings and the facefixings nearest to the mitres, being six nails in all, are
most likely to cause splitting and it is advisable to
blunt their points to reduce this risk. This is done by
holding the nail between forefinger and thumb, standing its head on a solid metal object or a concrete/brick
surface and tapping the point with a hammer.
16.1.6 Mitre Saw or Mitre Box
Figure 16.4(a): Traditionally, mitres used in secondfixing operations were always cut in a purpose-made
mitre box, but nowadays, as mentioned in the chapter
on tools, mitre (chop) saws are quite commonly used.
However, mitre boxes are still used and if one is to be
made, it should be at least 600 mm long, have a solid
timber base, as illustrated, of (ideally) 45 mm thickness and have plywood, MDF or Sterling board sides
of 18 mm thickness. The width of the base and sides
must be parallel and the base must be wide enough to
take a piece of architrave lying flat with at least 12 mm
tolerance. The sides must be wide enough to allow for
attachment to the base with sufficient upstand to
accommodate the skirting-height plus at least 10 mm
tolerance. The sides are nailed to the base with 50 mm
nails or screwed with 38 mm (1-12 in) countersunk
screws. The 45⬚ mitres must be marked and cut carefully with a panel or other fine-toothed saw. Once the
cut is about 10 mm deep, to avoid ‘cutting blind’, only
let the saw run in the opposite cut while increasing
the depth of the nearest cut, then turn the box around
and repeat this operation as many times as necessary
to control the plumbness of the cut.
(a)
(b)
Figure 16.4 (a) Mitre saw (b) Mitre box
16.1.7 Mitre Block
Figure 16.4(c): This is shown here for comparison with
the mitre box and although architraves can be cut on
it, the mitre block is more suitable for mitring smaller
sections like glazing beads and quadrant moulding,
cut with a tenon saw. When making one of these,
more precise mitring will be achieved if, as illustrated,
the solid top block is kept wide enough to give better
control of the back-saw within the extended mitre cut.
A piece of ex. 75 ⫻ 50 mm timber, about 450 mm
long can be used, lying flat on a 150 mm wide base of
18 mm ply, MDF or Sterling board. The mitres are
marked before screwing or nailing up through the
base, so that the fixings can be placed strategically to
avoid clashing with the 45⬚ mitred saw cuts.
Figure 16.4 (c) Mitre block
Architraves
16.1.8 Splicing
213
good fit thereto and, at the same time, achieve the
required margin. The scribing technique for this is indicated at A, in Figure 16.6(a) and is described as follows:
Figure 16.5 Leg-splicing
Figure 16.5: Ideally, each architrave member should be
in one piece, but sometimes there is a need to use up
the offcuts. The joining of two pieces is known as
splicing, which is done at 45⬚ across the face. Splicing
should never be done on a head piece and only be
done sparingly on the legs, as low as possible – well
out of eye level – and the splice, as illustrated, should
be cut to face downwards in the doorway. This tends
to make it less obvious.
16.1.9 Scribing
6 mm
margin
B
12 mm
overhang
1. With a minimum of temporary fixings, say two or
three, fix the unmitred leg to the lining’s edge and
establish a constant overhang of any amount, but
say 12 mm from the lining’s face.
2. Add the margin required, say 6 mm, to the overhangamount, making 6 ⫹ 12 ⫽ 18 mm. This is the
amount to be scribed from the wall-surface to mark
the architrave-cut. Most text books suggest that this
can be done with a pair of dividers, which is theoretically possible, but not very precise in practice. A good
practical way is to cut a small wooden block, equal in
thickness to the scribe-amount (18 mm), but minus
3 mm for half the pencil’s diameter, so that the pencil
held on the 15 mm thick block measures 18 mm to
the pencil point.
3. Holding the scribing block’s edges between the
second index finger and the thumb, place the
forefinger on the projecting pencil and mark/scribe
the architrave leg from top to bottom.
4. Release the leg from its fixings and very carefully
rip down on the waste side of the line, achieving a
slight undercut with the saw.
5. Try in position, then ease with a plane or Surform
file, if necessary. Mark and cut the mitre.
6. Fix in position. In the case of any small, undesirable gaps between the leg and the wall’s surface (as
at A in Figure 16.6(b)), the standard of work would
be improved if a small section of timber was glued
to the back edge and the increased width of architrave was scribed as before, finishing up like B in
Figure 16.6(b).
16.1.10 Double Architraves
Figures 16.7(a) and (b): In the case of two doorways
close together, separated by a partition wall, the architraves often come very close to each other on the side of
Pencil and
block
A
(a)
(b)
Figure 16.6 (a) Horizontal section showing scribing
technique; (b) horizontal section showing A, gap and B,
the infill
Figures 16.6(a) and (b): Where doorways are close to an
adjacent wall, very often the architrave leg on that side
touches the wall surface (B in Figure 16.6(a)) or, as
illustrated at A in Figure 16.6(b), leaves an undesirable
gap. In the first instance, the carpenter usually has to
‘scribe’ the architrave to the wall surface to achieve a
Figure 16.7 (a) Close doorways
the double doorway and again, small, undesirable gaps
can result, indicated in Figure 16.7(a). A small section of
timber can be glued in the gap, or as in Figure 16.7(b), a
double architrave can be produced or built-up and glued
214
Fixing Architraves, Skirting, Dado and Picture Rails
Figure 16.7 (b) Double architrave
together on site. This can be scribed or partly mitred
into a double door-head placed across both doorways.
16.1.11 Storey-frame Architraves
used when deep, built-up skirtings, often involving
one or two stepped face-boards, could not be mastered
at the doorway by the relatively thinner architrave.
Plinth blocks, therefore, are to accommodate the side
abutment of any skirting member which would otherwise be unsightly in sticking out past the face of the
architrave leg. The skirting was housed about 6 mm
into the plinth-block side to offset any shrinkage
across the block, and the base of the architrave leg was
half-lap jointed and screwed into the back of the
block, to make the block an integral part of the leg.
16.1.13 Cornice Blocks
Figure 16.8: Architrave legs that run up from floor to
ceiling are required in the case of storey frames or
Ceiling level
Figure 16.9 (b) Use of cornice blocks
(a)
(b)
Figure 16.8 (a) End-grain exposed; (b) end-grain
concealed
linings. These are doorways that incorporate a glazed
‘light’ above the door transom. Very often, the
architrave-head is required to be deeper to fit the ceiling
without violating the head-margin. This means that the
mitred legs will show unacceptable end-grain (Figure
16.8(a)), although the wider head can be partly mitred
into the legs (Figure 16.8(b)).
16.1.12 Plinth Blocks
Figure 16.9(a): The need for these may only now be
found on refurbishment works. Plinth blocks were
Plinth
block
Figure 16.9 (a) Use of plinth blocks
Figure 16.9(b): As with plinth blocks, cornices are not
found in modern buildings. They were at one time
used as an alternative to the mitred corners of a doorway, especially on higher class work where hardwood
linings, architraves and skirting, etc. were being used.
The cornice block, usually slightly thicker than the
architrave, was often carved or routered out in a decorative way. The leg and head architraves were simply
butted up squarely to it. The design of architraves
used on jobs involving cornices were often, as illustrated in Figure 16.10, either fluted, or reeded.
16.1.14 Architrave Shapes and
Sizes
Figure 16.10: Architrave sizes vary, but those quite
commonly used are ex. 50 ⫻ 19 mm, ex. 63 ⫻ 19 mm
and ex. 75 ⫻ 19 mm. On large jobs, architrave is usually ordered by the metre run, so it will arrive in random lengths, hence the occasional need for splicing.
On small jobs, it may be obtained in specified lengths
with head-lengths added together. A variety of modern and traditional shapes still in use are illustrated.
16.2 SKIRTING
Figure 16.11: Skirting is a protective board fixed at the
base of plastered or plasterboarded (dry-lined) walls,
which also covers the joint between the wall surface
Skirting
Splayed and rounded
(chamferred)
Single bevel edge
Ovolo
Single round edge
Double bevel edge
Fluted
215
Double round edge
Grecian ogee
Reeded
Figure 16.11 Skirting
Figure 16.10 Architrave designs
Figure 16.12 Internal scribe
and the floor. The depth of the skirting boards, for
visual balance, is usually at least 25 mm more than the
width of the architraves used; and the shaped or
moulded face-edge usually matches or is compatible
with the architrave.
purpose-made mitre box, but internal angles should
always be scribed. In effect, this means that the moulded
profile of the skirting is cut from the end of one piece, A,
to fit the moulded face of another piece, B, already fixed
squarely into the internal corner of the adjacent wall.
16.2.1 Scribing to the Floor
16.2.3 Scribing Internal Angles
If the skirting boards are reasonably straight-edged in
length and the floors are not uneven, it is theoretically
possible to fix the skirting without having to fit it to
the floor. Otherwise, it should be scribed. This is done
by positioning a length of skirting, then laying a pencil on the floor touching its face and running a line
along it. Next, the bottom edge is under-shot (meaning more planed off the back edge than the front) to
the line with a smoothing plane or Surform, used
diagonally across the edge, rather than along it, while
the skirting is laying face-up on a saw stool and the
planing action is aimed at the floor. This technique
allows the plane to remove any irregularities of the
floor-line more easily.
Figure 16.13: The professional technique for scribing
an internal angle in a 90⬚ corner is first to cut the end
16.2.2 External and Internal Angles
Figure 16.12: External angles are mitred, either with
the mitre saw mentioned previously, or with the
Figure 16.13 Scribing technique
216
Fixing Architraves, Skirting, Dado and Picture Rails
of the moulded board to be scribed with a 45⬚ mitre
cut A. This actually produces a sawn outline or profile
of the skirting’s moulded shape, regardless of whether
it is a simple, i.e. modern or complex traditional
design. Next, the scribe is produced by cutting in the
waste area of the mitred profile with a coping saw,
keeping very close to the outline with a slightly undercutting angle, as indicated in B.
16.2.4 Sequence of Fixing
1
6
7
2
A
3
4
8
Room
plan
9
16.2.6 Mechanical Fixings
Each piece of skirting is fixed as it is fitted, except when
a mitred corner is involved, when it is wise to fit the
two mitred pieces before fixing one of them. This way,
any adjustments to either mitre can be made more easily. Mechanical fixings, such as nails or screws, should
be made at approximately 600–800 mm centres. Nail
fixings must be punched in and screws should be countersunk or – especially in the case of hardwood skirtings
– counterbored and pelleted. Skirting fitted to timber
stud partitions can be fixed with 63 mm lost-head type
oval nails – and 63 or 75 mm cut clasp nails are still
good fixings for skirting being fixed to walls built with
receptive aerated building blocks. Walls built with
dense concrete blocks or brickwork can be drilled for
screw fixings. This is made easier nowadays by drilling
directly through the in situ skirting with a masonry drill
to take Fischer-type nylon sleeved Frame-fix screws.
16.2.7 Adhesive Fixings
5
10
B
Figure 16.14 Sequence of fixing
Figure 16.14: Even though well-fitted skirting scribes
may have been achieved, scribes should always face away
from the doorway, so that any slight gaps are not looked
directly into. This will always be possible, providing a
certain sequence of fixing is followed, from 1 to 10 as
illustrated in Figure 16.14. In the illustration, it can be
seen that skirting-pieces 1 and 6 are square-ended at
each end and pieces 4, 5, 9 and 10 have only one scribed
end – as do pieces 2 and 7, which are also mitred. The
message here is that you should always avoid having two
scribed ends on one piece of skirting board – because it
is much more time-consuming in demanding a higher
degree of precision and skill for it to be successful.
Avoiding double-ended scribes, therefore, is another
good reason for adopting a sequence of fixing.
16.2.5 Splicing
As with architraves, lengthening-joints (splicing)
should be minimal or non-existent. However, if they
are unavoidable – perhaps because of the long length
of a particular wall, or because there is an excessive
amount of offcuts to use up – the splice, which is
made with 45⬚ cuts across the top edges, should be
treated like the corner-scribes and always face away
from the direct approach viewed from a doorway, as
indicated in Figure 16.14 at A and B.
Figure 16.15 Temporary strutting
Figure 16.15: Present-day practices include fixing skirtings with so-called gap-filling panel adhesives such as
Laybond’s Gripfill or Connect. Gripfill is a solventborne, filled rubber resin and Connect is a solvent-free
gap-filling adhesive specially formulated to provide good
initial ‘grab’ or suction. Although either of these two
adhesives may be used, the Laybond Connect is recommended when bonding to vertical surfaces. These adhesives are in 310/350 ml cartridge tubes which fit into
silicone/mastic guns. Working speedily, one or two
6 mm diameter continuous beads should be applied to
the back of the skirting board, 25 mm in from the edges,
then it should be quickly placed and pressed (slid
slightly, if possible) into position. A few temporary nails
or pins may be needed if the skirting appears to come
away from the wall in places. These should be left in
overnight. Alternatively, as illustrated, small struts
(maybe offcuts of skirting) can be wedged against the
Dado Rails and Picture Rails
skirting, taking a foothold from short battens or offcuts
fixed temporarily to the floor. If the floor has been
overlaid with hardwood or plastic laminate flooring,
temporary fixings could not be made and struts might
need to be taken across to an opposite wall.
16.2.8 Skirting Shapes and Sizes
Splayed and
rounded
(chamferred)
Single round Grecian
edge or
ogee
bullnose
Ovolo
16.3 DADO RAILS AND
PICTURE RAILS
Figure 16.16: Like architraves, skirting sizes vary, but
those most commonly used are ex. 75 ⫻ 19 mm, ex.
100 ⫻ 19 mm and ex. 150 ⫻ 19 mm. If required, the
thickness of these skirting boards can be obtained
increased to ex. 25 mm, but this would mean increasing
the architrave-thickness. Again, like architraves, it is
usually ordered by the metre run, so it will arrive in random lengths. A variety of modern and traditional shapes
still in use are illustrated. Also of course, on certain jobs
where simplicity is sought and moulded shapes are
being avoided, plain square-edged boards may be used.
16.2.9 Dual Pattern Skirting
Figure 16.17(a)(b)(c): In recent years, dual pattern skirting of various depths has gained in popularity. The
main advantage is that it offers a choice of moulded
design on its alternate faces. Another advantage, not
(b)
always realized, is that whatever edge touches the floor,
it has the effect of being ‘undershot’, by being relieved
in thickness by the unseen moulding on its back face.
This reduced edge-thickness makes it much easier to
scribe – if necessary – to an uneven floor. However,
there is also a downside: the lower face of the skirting is
less solid (more so with the Grecian ogee, less so with
the bullnose) and tends to cup slightly. This is sometimes quite noticeable on mitred external angles, which
cannot be overcome by pinning, because of the absence
of lower back-face material.
Finally, MDF is also used for moulded skirting
nowadays. It has a good, smooth finish, is mitred and
scribed satisfactorily, responds well to adhesive and
screw fixings, but does not receive nails very well and
offers more resistance to being scribed to uneven
floors – requiring more effort and a sharp plane.
Torus
Figure 16.16 Skirting designs
(a)
217
(c)
Figure 16.17 (a) ex 25⫻175 mm chamferred/ovolo
skirting; (b) ex25⫻150 mm bullnose/chamferred skirting;
(c) ex25⫻175 mm Grecian ogee/Torus skirting
Figure 16.18 (a) Dado rail; (b) picture rail
Figures 16.18 (a) and (b): In recent years there has been a
degree of revival of these traditional items, especially on
home-improvement schemes. Basically, the same rules
and techniques regarding mitring, scribing, splicing,
fixing, etc., apply to dado and picture rails as already covered regarding the fitting and fixing of skirting. Dado
rails of usually ex. 75 ⫻ 38 mm section, of whatever
moulded design, are fitted and fixed around the walls of
a room at about 900 mm up from the floor. Whatever
height is used, the dado rails should be kept parallel to
the floor, regardless of exact levels. Picture rails of about
ex. 50 ⫻ 25 mm section, of whatever moulded design,
but with the essential grooved or rebated top edge (as in
Figure 16.18(b)) to hold the picture hooks, are fitted and
fixed around the walls of a room, usually at the level of
the top of the architrave-head of the room’s doorway.
Whatever height is used, the picture rails should be kept
parallel to the ceiling, again regardless of levels.
17
Fitting and Hanging Doors
17.1 INTRODUCTION
Door-hanging is a vital part of second-fixing carpentry and requires a good standard of workmanship and
speed. One, to one and a half hours is the established
hanging-time for a lightweight internal door and two
and a quarter hours for a heavy external type or fireresisting door. When hanging a door on a solid,
rebated frame, this time includes fitting the door
properly into the rebates – and on a door lining, it
includes adjusting and fixing the planted door stops
after the door has been hung. When more than one
door is to be hung in the same locality, time will be
saved by treating the fitting of locks and door furniture as a separate, secondary operation.
between the horns (Figure 17.1). Without the horns,
the additional timber would have to cross the opposing
grain of the stiles, which is bad trade practice, not allowing for natural shrinkage (Figure 17.2).
17.2.2 Checking the Opening Size
17.2 FITTING PROCEDURE
Nowadays, with a few exceptions, horns are usually nonexistent or very minimal in size. Although openings with
non-standard height may only be met occasionally –
usually on older-type property with odd-sized doors – it
will be sensible on certain jobs other than new works,
not to cut the bottom horns (if they exist) until the
height of the door opening is checked. This can be done
with a pinch rod or tape rule, although, if no major discrepancy is suspected, it will be quicker to hold the door
against the opening and mark the top and side edges
onto the frame, thereby gaining visual evidence of the
amount to be planed off.
17.2.1 Removal of Horns
17.2.3 Checking the Hanging Side
Room
Bottom rail
Immediate loss
of privacy
Room
Figure 17.1 Increasing door-height
Gradual loss
of privacy
Figure 17.3 Hanging side
Shrinkage
Figure 17.2 Bad practice
Figures 17.1 and 17.2: Traditionally, all doors (including
flush doors) arrived on site with horns left on to give
protection to the corners of the stiles. This also made it
possible to increase the height of a door, if required, by
gluing an additional piece of timber to the bottom rail,
Figure 17.3: On which side the door hangs and whether
it should open in or out, must be known. This information can be found on the plan views of the contract
drawings, although sometimes a member of the site
management team takes the responsibility of checking
this out and marking the hinged side of the lining or
frame with the letter H, at about one metre from the
floor. Another guide, if needed, is that the lock edge of
the door should be on the side nearest to the light
switch at the side of the opening. Of course, on new
contracts, this assumes that the electrician has put the
Fitting Procedure
switch in the correct position. On small contracts,
where the builder or carpenter himself might decide
on which side to hang the door, it may help to know
that doors should give maximum privacy to a room
while being opened (Figure 17.3). Another point to
bear in mind on this subject, is that normally, external
doors should open inwards, to avoid damage if caught
by the wind in a partly open position.
17.2.4 Tools Required
The following tools are required to cover a variety of
door-hanging jobs: pencil, tape rule, combination
square, panel-type saw, size 5-12 jack plane and/or a
4 -12 smoothing plane, optional power or cordless
planer, one or two marking gauges, 32 mm beveledged chisel, claw hammer, optional mallet (for chisels
with boxwood handles), large-sized birdcage awl with
square tapered point, cordless screwdriver, portable
router and hinge jig, bullnose rebate plane, or a shoulder plane with a removable front section (for easing
rebates on solid timber frames), nail punch (for
planted door stops), and a sharp marking knife (for
scoring across the plies or veneers of flush doors, if
they are to be reduced in height).
17.2.5 Equipment Required
Figure 17.4 Extension stool-top
100
A
150
25
50
B
50
300
∗
Back block
600
100
50
Front saddle
Figures 17.4–17.6: The equipment required for doorhanging can be as simple as one saw stool and an ex.
100 ⫻ 25 mm board of about 1 m length with a V cut
in one end. The board, shown in Figure 17.4, can be
screwed onto the top of the stool as and when
required and helps to hold the door on its edge during
the planing or shooting-in operation indicated in
Figure 17.6. Additionally, a device known as a saddle
and block, detailed in Figure 17.5, and easily made
from two pieces of 100 ⫻ 50 mm timber, provides a
very simple but effective way of holding the door
firmly while shooting-in or cutting out the housings
for the hinges, as indicated in Figure 17.6. A second
saw stool is occasionally required to act as a trestle
should it be necessary to lay the door across both
stools to cut the horns or the bottom of the door.
17.2.6 Skilful Planing Requirement
When shooting-in the door, it is good practice to
remove an equal amount from each side. This is done
by judgement, rather than measurement. If the
amount to be removed is in excess of a few millimetres,
a power or cordless planer, if available, would save a
lot of effort. However, to eliminate the unsightly
rotary cutter marks that can be left on the door-edges,
especially if the planer is pushed along too speedily,
the edges should be finished off with a jack or
smoothing plane. Although, unskilful hand planing –
by not putting the correct pressure and momentum to
the plane, or by not lifting off correctly (by raising the
heel) – produces ridges and chatter marks which can
be as unsightly as the pronounced rotary-cutter marks.
17.2.7 Closing Edge
∗
∗∗
Door
∗ Wedge can be cut
from here
Figure 17.5 Saddle and block
∗∗
∗
Door
A
Door in
the saddle
for planing
B
Figure 17.6 Door held firmly against saw stool
219
∗∗ = clearance angle
∗ = 2 mm joint
Figure 17.7 (a) Horizontal sections showing closing
edge of door
220
Fitting and Hanging Doors
Figure 17.7(a): The closing or lock edge of a door
requires a slight angle of about 87–88⬚ to clear the
frame or lining’s edge effectively. This should be
achieved while shooting-in and not added afterwards.
Again, this is done by judgement, rather than measurement. Although, until experience is gained, a sliding bevel could be set up and used for testing the edge
while planing. The clearance angle in relation to the
jamb’s edge is indicated in Figure 17.7(a).
17.2.8 Clearance Joints
∗
Door
∗∗
∗
Door
∗∗
∗∗ = 1 mm clearance joint
∗ = 2 mm joint
Figure 17.7 (b) Horizontal sections showing hanging
edge of door
Figure 17.7(b): A consistent and unwavering 2–3 mm
joint (gap) should be achieved around the door and
frame or lining (side-edges and top) and the joint at the
bottom should be a minimum 3 mm and a maximum
6 mm, unless extra allowance is required for floor covering, such as carpets. A two-pence coin is sometimes
used as a feeler gauge for testing the top and side joints.
happens if these edges touch. The size of planted door
stops varies in section between ex. 50 ⫻ 12 mm and
ex. 38 ⫻ 12 mm, or ex. 50 ⫻ 16 mm and ex.
38 ⫻ 16 mm and requires fixing every 225 mm
approximately, with 38 mm lost-head oval nails, staggered and punched under the surface by at least 1 mm.
Solid frames with sunken rebates can present more
problems than linings with planted stops, because the
door must fit well into the rebates and if it – or the
frame – is twisted, this will involve easing the shoulders of the rebates with a shoulder or bullnose plane.
17.2.11 Various Points to Note
1. When hanging hardwood doors, especially hardwood flush doors, or any door which may be easily
surface-damaged, the door should be protected
from being scratched or bruised by covering any
door-bearing stools with dust sheets or soft fibreboard. For the same reasons, the door-side of the
housing in the saddle block and the door-side of
the wedge should be covered with masking tape.
2. When removing horns, or cross-cutting plywood or
veneer-faced doors to reduce the height, spelching
out of the fibres can be eliminated if the amount to
be cut off is heavily scored with a sharp marking
knife or chisel on both sides, then, after being cut
very close to the line, is finished off by planing
down to the knifed edge.
3. If more than 6 mm has to be removed from the
bottom of a door, it is advisable to rip this off by
saw. Any lesser amount should be planed, but first
consider removing the cross-grain of the stiles, if
practicable, with a fine saw, to make easier work of
the planing, as indicated in Figure 17.8.
Flush door
Bottom rail
17.2.9 Arrises
After shooting-in the door and before screwing on the
butt hinges, it is important to plane off the ‘arrises’
(sharp corner edges) from the top, bottom and side
edges on both sides of the door. The appearance of
this should be like a miniature chamfer, measuring no
more than 1–1.5 mm across the 45⬚ chamfer. Usually,
one or two strokes with a smoothing plane will
accomplish this.
17.2.10 Planted Door Stops and
Sunken Rebates
Figure 17.7(b): The door stop or the sunken-rebate
shoulder must be 1 mm clear of the door on the
hanging side, to avoid a fault known as binding, which
∗
∗
∗
∗
∗ = End-grain removed prior to planing
Figure 17.8 Reducing door height
17.2.12 Doors on Rising Butts
Figures 17.9 and 17.10: Doors being hung on rising
butt hinges require the inner top edge of the door to
be shot off on the splay. The amount of splay to be
planed off is shown in Figure 17.9. Rising butt
hinges are either left-handed or right-handed and a
satisfactory way to identify which hand is needed is to
name the hand facing the door as it opens away from
you, as shown in Figure 17.10.
Fitting Procedure
6 mm
225 mm
Amount to
be planed
off the inner
top-edge
221
Figure 17.11: There are no hard and fast rules about
hinge positions, but they should always be less at the
top than the bottom and must be clear of the end
grain of any mortices (or their wedges) by at least
12 mm. Positions of 150 mm down to the top of the
butt and 225 mm up to the bottom of the butt are the
usual settings – but this may be governed by other
doors already hung in the vicinity by others who used
settings of 175 mm down and 250 mm up; in this case,
their settings are followed. If three butts (1-12 pairs) are
specified or decided upon for a heavy door, the additional butt must be equidistant between top and bottom butt-positions, as in Figure 17.11.
17.2.14 Hinges and Screws
Figure 17.9 Rising butts
Right hand
Left hand
Figure 17.10 Handed hinges
17.2.13 Hinge Positions
Butt hinges range in type and in size from 25 mm to
150 mm (75 mm and 100 mm being most commonly
used), and come in various kinds of metal. Screws
should always match and may be recessed for
Supadriv/Pozidriv, Phillips, etc., screwdrivers. Mild or
bright steel butts must be painted in with the door,
but brass or other non-ferreous metal butts, used on
exterior or hardwood doors, should not be painted.
The screw gauge must suit the countersinking in the
butts, but the screw length is usually from 32 mm (1-14
in) to 38 mm (1-12 in). On lightweight doors, 25 mm (1
in) screws are often used. A reasonably accurate way of
determining the gauge of a screw is simply to measure
across the head of the screw in millimetres, i.e., 6 mm
diameter ⫽ gauge 6, 8 mm diameter ⫽ gauge 8,
10 mm diameter ⫽ gauge 10 and so on. Another way
is to measure the diameter of the shank in millimetres
and double it to give the gauge, i.e. 3 mm diameter
shank ⫻ 2 ⫽ gauge 6 screw.
17.2.15 Knuckles In or Out
Figure 17.12: This illustrates different settings for butt
hinges in relation to the knuckle part of the hinge, as
follows.
Figure 17.11 Hinge positions
(a) The butts are housed with a full knuckle projection. This is now standard practice to save time.
(b) The butts are housed-in to lessen the knuckle
projection for aesthetic reasons, but, to enable
the door to open beyond 90⬚, the centre of the
knuckle must not be further in than the surface of
the door.
Although chiselled chamfers were used to accommodate the recessed knuckle, excessive time was
added to the door-hanging operation and, therefore, this practice has not survived.
(c) In this example, only the knuckle on the frame
side is partly housed-in to carry the door further
222
Fitting and Hanging Doors
Figure 17.13: When the door has been shot-in and the
clearance-joints have been achieved, set up the door in
the opening as follows: insert an off-centre wedge,
chisel or bolster under the door and lightly tighten up
to a two-pence coin placed in the top, as illustrated,
and then insert a small wedge at mid-height in the
joint of the closing stile (the doubled-joint obtained
this way can be tested, if necessary, with two twopence coins held together and tried in several places
(or slid along) above and below the wedge). Mark the
hinge positions now, squarely across the frame or lining
and the door. Alternatively, the butts could be already
housed-in and screwed to the door before it is positioned in the opening and the unfolded leaves of the
butts could then be marked onto the frame or lining.
17.2.17 Marking the Housings
Figure 17.12 Knuckle projections
into the shoulder of the jamb, when a rebate is
deeper than the door thickness (which is met
occasionally). If ignored, an excessive clearancejoint between the shoulder and the door would
look unsightly.
Figure 17.14 (a) Determining housing-depth
17.2.16 Marking the Hinge Positions
Two-pence coin
H H
Door
in
position
Wedge
Figure 17.14(a): The door is now removed from the
opening and set up in the saddle and block ready to be
hinged. Place an open butt on the edge of the door,
with the protruding knuckle inverted to rest against the
edge, locate carefully to the correct side of the face
mark and scribe around the leaf with a sharp pencil.
Repeat this on each of the four butt-positions. Next,
adjust the leaves of the butt until parallel (as illustrated), measure the overall thickness, deduct 2 mm for
the joint, then divide by two to give the depth of housing required and set this on the marking gauge. Mark
the butt-positions with this on the face of the door and
the edge of the frame or lining. Then reset the gauge to
the leaf-width of the butt and mark this on the edge of
the door and the face of the frame or lining.
17.2.18 Cutting the Housings
H H
Wedge
Figure 17.13 Marking hinge-positions
Figure 17.14(b): Now cut the housings, using the chiselchopping method, prior to chisel-paring.
When leaning the chisel (at about 45–50⬚) for the crossgrain chopping action, the chisel’s bevelled-edge should
be on the side of the acute angle formed between the
chisel and the timber. Note that if the housings are cut
too deeply, the hinge-side joint will be lost and binding
may occur between the door-edge and the face of the
Hanging Procedure
Chisel positioned
in gauge line
223
5. Now concentrate on judging, marking and
shooting-in the right-hand stile only, until (with
the door pressed hard to the left) you are able to
test for a double-joint with the aid of two twopence coins held together.
6. If satisfied, re-establish the side and bottom
wedges (Figure 17.13), after inserting a twopence coin in the top joint. Now mark the hinge
positions on the door and lining-edge.
7. Dismantle and remove the arrises from all door
edges before fixing the butts to the door.
8. Mark and cut out the housings for the butts, try
the butts in lining-housings and make a pilot hole
for one screw in each butt.
9. Screw butts to door, hang door and try closing
and check the all-round fit.
10. Remove and adjust, if necessary, or finish
screwing to the lining.
11. Fix top door stop (1 mm clear on hinge-side
only), then closing edge door stop, then hanging
edge door stop. Finally, punch in all nails.
Figure 17.14 (b) Cutting the housings
17.3.1 Use of Portable Router and
Hinge Jig
frame or lining. Also, if the wrong gauge screws are used
and the countersunk heads protrude, binding may occur
between the opposite screw heads.
Nowadays, the door-hanging procedure is often
speeded up by using a router and a hinge jig, both
described and illustrated in sections 2.18 and 2.19 in
chapter 2. To take these into account here, the hanging procedure listed above would be changed as follows, after procedure number 5 had been completed:
17.3 HANGING PROCEDURE
Speed and skill in door-hanging is gained from the
experience of repetition and it will assist if you adopt
the set hanging procedure described below. (Note that
the references are to a door-lining, but the procedure
would also suit a door-frame.)
1. Check the opening size and hanging edge. Mark
H on the lining face, mark T (for ‘top’) on the
face of door (this is to avoid mistakenly changing
the face-side during the shooting-in procedure)
and remove horns, if necessary.
2. Offer the door up in position, judge the initial
amount to remove from the edges and shoot-in.
3. Offer up again – if it now fits into the opening,
concentrate on marking and planing the left-hand
stile only, until a good fit is achieved against the
lining-leg.
4. While keeping the door pressed or wedged
against the left, lever or wedge up the door and
check the fit against the underside of the lininghead. Remove the door and plane the top, if necessary, until another good fit is achieved.
6. If satisfied, remove the door and plane off the
sharp arrises from all edges. Set the door up in the
saddle and block, ready for hinging.
7. Now attach the hinge jig to the door lining, making sure that the swivel plate is at the top to
establish the 3 mm top-joint allowance. Set up the
router and rout out the hinge recesses.
8. Remove the hinge jig and set it up on the edge of
the pre-positioned door. Make sure that the
swivel plate is turned at 90⬚ and hooked onto the
top of the door. Rout out the hinge recesses and
remove the jig.
9. Some butts have rounded corners to fit the
routed recesses, but if standard butts are being
used, then chisel out the rounded corners from
the four (or six) recesses. Fit the butts in the lining-recesses and make a pilot hole for one screw
in each butt.
10. Screw butts to door, hang door and try closing
and check the all-round fit. Remove and adjust, if
necessary, or finish screwing to the lining.
11. Fix top door stop (1 mm clear on hinge-side
only), then closing edge door stop, then hanging
edge door stop. Finally, punch in all nails.
18
Fitting Locks, Latches and
Door Furniture
18.1 LOCKS AND LATCHES
and turning a key. The concealed part of the bolt, as
illustrated, has a small metal post protruding from it,
which must be moved through an open gate cut in the
middle area of a specified number of sprung levers.
This happens when the key lifts the levers, gains access
to the edge of the bolt and moves it. The more levers a
lock has, the greater the security. The quadrant-shaped
latch is usually reversible to enable the hand of the lock
to be changed from left to right, or vice versa.
Face plate
Follower and
spindle brush
18.2 MORTICE LOCKS
Case
Reversible
spring-loaded
latch
Post
Bolt
Sprung levers
Gate
Figure 18.1 Mortice-lock mechanism
Figure 18.1: The types of lock used on dwelling houses
are few and vary between locks, latches and combinations of these two. They may be mortice locks morticed into the door-edge, or various types of rim lock
fixed on the inside face-edge of the door. The actual
latch part of a lock is usually spring-loaded, quadrant
shaped, or has a round-edged roller bolt, which holds
the door closed (latches it) without locking it – unless
it is a type of cylinder night latch, which requires a
latch-key to open it on the cylinder-side of the door.
The locking mechanism of a mortice lock is usually an
oblong-shaped bolt which is shot in or out by inserting
(a)
Figure 18.2 (a) Shallow mortice lock
Figure 18.2: These locks vary in length (depth)
between 64 mm and 150 mm. The deeper locks
(Figure 18.2(b)) are of traditional size to receive doorknob furniture which consists of a spindle, two knobs
(sometimes one of these is already attached to a metal
spindle, the other being removable via a small grub
screw), two rose plates, and two escutcheon plates
(Figure 18.2(e)). The shallow-depth lock (Figure
18.2(a)) has its keyhole and spindle hole vertically in
Mortice Latches
225
possible scraped knuckles. If door knobs are to be
used, the lock should be at least 112 mm (4--12 in) deep.
18.3 MORTICE LATCHES
(b)
(c)
(a)
(b)
(d)
Grub
screw
Spindle
Round-shaped
escutcheons
Elliptical-shaped
escutcheons
(c)
Loose knob
Roses
Knob fixed to spindle
(e)
Figure 18.2 (b) Deep mortice lock; (c) striking plate (brass
or chromed steel); (d) lock lever-furniture; (e) door knob
furniture
line to receive a set of lock lever-furniture (Figure
18.2(d)). Both types of lock have a striking plate
(Figure 18.2(c)) which is housed into the jamb to
receive the projecting latch and the turned bolt.
Shallow-depth locks should only be fitted with lever
furniture, as door knobs come too close to the face of
the jamb or lining on the door-stop side, resulting in
Figure 18.3 (a) Mortice latch; (b) tubular mortice latch;
(c) latch lever-furniture
Figure 18.3: Mortice latches are used on internal doors
not requiring to be locked. Two types are available: one,
as in Figure 18.3(a), is oblong-shaped for morticing in
to a 16 ⫻ 38 mm ⫻ 64 or 75 mm deep mortice hole; the
other, as in Figure 18.3(b), is tubular-shaped for inserting into a drilled hole of 22 mm diameter ⫻ 64 or
75 mm depth. A mortice latch is always supplied with a
striking plate and fixing screws, but requires separately a
set of latch lever-furniture (without the keyhole), as
shown in Figure 18.3(c).
226
Fitting Locks, Latches and Door Furniture
18.4 MORTICE DEAD LOCKS
(a)
Jamb
Note
Rim latch set in further
from edge, jamb housed
and quadrant latch
reversed
Rim
latch
Figure 18.4 Mortice dead-lock and box-recessed striking
plate
Door
Figure 18.4: Mortice dead locks are for extra security
and contain only a locking bolt – no latch. They are
fitted to external doors in addition to a latch-type cylinder lock and are recommended by insurance companies
to have five levers. The more expensive locks of this kind
have a box-recessed striking plate or keep – and the brass
bolt contains two hardened steel rollers to resist being
cut with a hacksaw blade. Ironically, these locks can be
more of a deterrent on the inside of a property than on
the outside. The reason for this is that if burglars have
gained access through a window – which is quite common – they like to leave by a door, which is less suspicious, easier and quicker than carrying stolen goods
through a window. My preference with these locks is to
make a keyhole only on the outside of the door, which is
done to stop anyone deadlocking themselves in the
property at night, in case there is a fire. The only door
furniture required is supplied in the form of two
escutcheons, one being a drop escutcheon with a pivoting
cover plate that drops down to cover the keyhole on the
inside of the door, as shown in Figure 18.2(e).
∗ Special striking plate
∗
Cylinder
18.5 CYLINDER NIGHT LATCHES
Figure 18.5(a) and (b): This type of lock/latch is commonly used on front entrance doors and consists of the
rim latch itself, as illustrated, with a turn-knob and a
small sliding latch-button for holding the latch in an
(b)
Figure 18.5 (a) Part horizontal section through normal
inward-opening door; (b) uncommon outward-opening door
open or closed (locked) position, a cylinder with a bar
that connects into the latch, a loose rose plate that provides a rim for the cylinder (or alternatively, a cylinder
door pull), a back plate with connecting screws for
securing the cylinder to the door and a box staple (also
referred to as a keep) for receiving the striking quadrant-shaped latch. These locks are obtainable in standard sizes or narrow sizes. The latter is sometimes
required on glazed entrance doors with narrow stiles.
A standard cylinder night latch requires a 32 mm (1--14
in) diameter hole to be drilled through the door at
61 mm in from the edge to the centre, to receive the
cylinder. The narrow latch type requires the same size
hole to be drilled, but at 40 mm in from the edge to
the centre.
18.6 FITTING A LETTER PLATE
Figure 18.6: Measurements for the oblong aperture
must be carefully taken from the letter plate and plotted
on the outside and the inside face of the door. This can
Fitting a Mortice Lock
Jigsaw method
Hand method
Vertical
section
227
the required area for the letter plate, a jig template
such as the Trend model illustrated at Figure 18.6, is
screwed in position. The router is set up and worked
around the template to achieve a fast and precise
finish. When complete, the template is unscrewed and
the two screw holes become the centres for the small
bolt holes to be drilled through the door to hold the
letter plate. Certain makes and models of router might
require a universal sub-base to accept the 30 mm guide
bush needed for this template.
(a)
18.7 FITTING A MORTICE LOCK
Figure 18.7: The following technique for fitting a standard mortice lock can – with the omission of the spindle
00
⫻
60
mm
2
10
⫻
60
mm
2
0⫻
50
mm
22
(b)
Figure 18.6 (a) Fitting a letter plate (three methods);
(b) letter plate jig. Jig template/router method
best be done by marking a level centre line, as illustrated, on each face, to use as a datum line for the
other measurements. This is also the line on which to
mark the critical position of the 6 mm diameter holes
to be drilled for the connecting bolts. If confident
of the accuracy of your marking out, these holes are
best drilled halfway through from each side. Slight
misalignments midway can be overcome by the
reaming effect gained by using a Sandvik combination
auger bit.
The aperture can be cut out easily with a good jigsaw. Note that when reaching each corner, the saw is
worked back and forth a few times to create space for
the blade to turn through 90⬚. When cut, the hole is
then cleaned-up with a wide bevelled-edge chisel
and/or a Surform file.
Alternatively, a line of large-diameter holes can be
drilled, with smaller holes drilled at each end to make it
easier to cut the end grain with a sharp bevelled-edge
chisel. By using this hand method, once the ends are
chopped through from each side, the remaining timber
above and below the large holes pares out quite easily
with a wide bevelled-edge chisel. The exposed arrises of
the aperture should be removed with a chisel and/or
glasspaper.
Another method used nowadays, is to cut out the
aperture with a -12⬙ (12.7 mm) collet plunge router.
After pencilling vertical and horizontal centre lines in
5
6
2
6
6
4
1
8
4
10
9
5
3A
3B
7
4
12
(a)
(b)
Figure 18.7 (a) Fitting a mortice lock. Hand method;
(b) fitting a mortice lock. Router and jig method
228
Fitting Locks, Latches and Door Furniture
hole – be modified for fitting a mortice dead lock. The
auger bits used can be power-driven or fitted into a
ratchet brace. If power-driven, the drill must have a
reversing facility and, ideally, a variable speed.
1. If no predetermined height exists, measure down
half the door’s height to mark the spindle level
and square this around the door.
2. Measure the lock from the outer edge of the face
to the centre of the spindle hole and mark this on
the door on each face with a pencil line gauged
from the blade-end of the combination mitre
square. Make a slight allowance for the undershot
edge of the door.
3. Measure the lock vertically from the centre of the
spindle hole to the top-centre and bottom-centre
of the keyhole and mark cross-lines A and B on
both faces of the door.
4. Hold the lock against the door, sight through
the spindle hole to line it up with the spindle
cross-mark, then mark lightly around the outer
edge of the lock.
5. Square this outline across the edge of the door.
6. Set up a marking gauge and mark the centre of
the door thickness, then reset the gauge to be
8 mm from the centre and mark a line on each
side of the first gauge line.
7. Drill a 10 mm diameter hole at 3A and a 6 mm
diameter hole at 3B, preferably from each side of
the door to avoid spelching out.
8. Drill a 16 mm diameter hole for the spindle, again
from each side of the door.
9. As indicated, drill a series of 16 mm diameter
holes close to each other for the lock-mortice. Use
a depth gauge on the drill or bind masking tape
around the auger bit to achieve a slightly oversize
depth. Hold a flat rule or the blade of the
combination square on the face of the door when
drilling, to check on drill-alignment occasionally.
10. Clean out the mortice hole with, say, a 25 mm
bevelled-edge chisel and a 16 mm firmer chisel.
On mortices for deep locks, a so-called swan-neck
chisel is sometimes necessary.
11. Complete the keyhole shape with a small chisel or
a pad saw.
12. Try the lock in the mortice until, after easing, you
achieve a slightly loose fit, then adjust it for central
position edgewise and mark around the face plate
with a sharp pencil. The edge-lines can be scored
heavily with a marking gauge to reduce the risk of
splitting the edges with a chisel, then chisel-chopping across the grain is carried out before handroutering the face-plate depth, by judgement with
the chisel held in a position similar to when it is
being sharpened. Keep trying the lock until it fits
slightly under the surface. Then screw into position.
13. Now close the door a few times until the latch
marks the jamb’s edge, or mark this position with
a pencil, and square these marks across to relate to
the striking plate’s mortice hole. Position the
striking plate onto the protruding latch and mark
the plate’s face where it protrudes past the face of
the door. Now hold the striking plate against the
marks on the jamb, with the edge-mark on the
plate in line with the jamb’s edge and mark
around the plate with a sharp pencil.
14. Carefully chop out a shallow housing for the
striking plate and try in position. Mark the outline
for the latch and bolt mortice holes, remove the
plate and drill/chop out for these. Fix the striking
plate and try closing the door for easy latching
and locking.
Another method used by some carpenters, is to cut the
mortice out with a heavy duty plunge router which, as
before, has a 1/2⬙ (12.7 mm) collet. A lock jig such as the
Trend model illustrated at 18.7(b) is clamped to the
door securely to guide the routing. Again, the router
will require a 30 mm guide bush and a 12 mm
Ø ⫻ 114 mm long-reach TCT cutter. This will cut up
to a 70 mm deep mortice. Mortices for deeper locks will
require finishing off with an auger bit and drill – or a
twist bit and brace. The magnetized, interchangeable
templates on this jig, allows both the mortice and the
shallow face-plate recess to be cut.
18.8 FITTING DOOR
FURNITURE
When fitting the door furniture, which is usually done
after the doors have been painted or sealed, or – better
still – has been done previously and then removed and
replaced after painting or sealing, care must be taken
with the vertical and lateral positioning and screwing
of the furniture. This is because the 6.35 ⫻ 6.35 mm
square-sectioned spindle sits quite loosely in the lock’s
spindle bush and if strained over to one extreme or the
other by ill-positioned screws in the door furniture,
binding can occur which may cause the latch and the
lever handles or knobs to stick in the levered or turned
position, without the springs being able to effect a
self-return action. To avoid this, always feel for the
correct position by gently moving the furniture from
left to right and up and down – and by settling in the
middle of these extremes. To help with this, on lock
lever furniture, the keyholes can be sighted through
for alignment. After fixing, always check lever handles
or knobs for a smooth, easy movement and a selfreturning action.
19
Fixing Pipe Casings and
Framed Ducts
19.1 INTRODUCTION
Occasionally, according to the design of a property,
there is a need to conceal vertical and/or horizontal
pipes to improve the appearance of the room(s) that
they pass through. These rooms are usually the bathroom or kitchen. The pipes may be 110 mm diameter
soil pipes, 40 mm diameter waste pipes, or various
small-diameter copper supply pipes. If the supply
pipes are fitted with stopcocks, provision must be
made for their access when the pipes are to be concealed. Basically, the two arrangements for concealing
pipes are pipe casings and framed ducts.
19.2 PIPE CASINGS
Figure 19.1: Traditionally, solid timber of about 225 mm
prepared width was used in the construction of pipe casings. The side casing had a beaded and rebated edge to
receive a thinner timber casing. Vertical battens of about
50 ⫻ 25 mm section were fixed to the finished wall surfaces, carefully positioned laterally to ensure that the
completed casing fitted squarely in the corner and was
square in itself. Any under-achievement in this respect
showed up badly at ceiling and floor levels. When working out the lateral position of the battens in relation to
the width of each casing, allowances had to be made if
it was decided that the casings would need to be scribed
to the walls. Modern pipe casings are of similar
Figure 19.1 Horizontal section through traditional
pipe casing
construction, but the timber casings have been replaced
by plywood or MDF of usually 12 mm thickness, with
the rebated edge in the form of a planted, vertical
corner batten, as at detail A.
19.3 FRAMED DUCTS
Figure 19.2: Framed ducts take over from ordinary
plywood or MDF casings when there are a greater
number of pipes to conceal, or the concealment involves
a more complex arrangement of vertical and/or horizontal pipework. The sawn or prepared timber framing
may be of 50 ⫻ 50 mm, 50 ⫻ 38 mm or 38 ⫻ 38 mm
section. As illustrated, vertical or horizontal battens of
50 ⫻ 25 mm section are still used as before to establish
the ducting’s position and anchorage to the walls or – in
cases of horizontal ducting – to the wall and the floor
or the wall and the ceiling. The other framing consists
of a longitudinal corner-member and cross-noggings
spaced at 600 mm centres. The framing is built up in
situ, like stud partitioning. The butt-jointed noggings
are skew-nailed to the longitudinal battens and nailed
through the corner member at the other end. When the
skeletal framework is completed, it is then covered with
6 mm or 12 mm plywood or MDF. If future access to
the pipes or stopcocks is required, the face panels
should be neatly screwed.
Figure 19.2 Horizontal section through modern
framed duct
20
Designing and Installing
a Fitted Kitchen
The first fitted kitchens are believed to date back to
the late 1920s and mostly involved cabinet makers
and second-fixing carpenters. Nowadays, however,
with all the hi-tech fittings and equipment available –
plus the manufacturing, fitting and fixing of purposemade solid worktops such as granite, quartz/polymer
resin, and Corian® (-13 acrylic resin and -23 natural mineral) – designing and installing fitted kitchens tends
to be done by specialists. Nevertheless, if only for
financial reasons, non cutting-edge kitchens using
plastic-laminate and solid timber worktops still predominate – and a large number of kitchens are still
installed by non-specialists. Anyone with good carpentry or DIY skills and a commonsense approach to
design, is capable of successfully designing and
installing a standard fitted kitchen.
Figure 20.1(a): In the early 1950s, researchers in
Cornell University in New York, USA, conceived the
idea of the work triangle as being the geometry determined by the positions of the sink, the refrigerator
and the cooker. These were identified as the three
main centres in a kitchen involving traipsing backwards and forwards during the cooking task. Study
revealed that an ideal imaginary line joining the sink,
fridge and cooker should measure no more than 20 ft
(6.1 metres). It has also been established that the distance between opposing worktop-edges, as in a narrow, so-called galley kitchen, should be no less than
4 ft. (1.219 m).
Sink
Preparation
surface
Fridge
20.2 ERGONOMIC DESIGN
CONSIDERATIONS
Sink
Worktop
Worktop
Dishwasher
NLT Cooker
400 mm
20.1 INTRODUCTION
Minimum
1.2 m
Figure 20.1 (b) Design considerations
Worktop
Fridge
under worktop
Figure 20.1(b): Other design considerations that
should be taken into account when juggling with the
work triangle are:
●
Cooker
Figure 20.1 (a) Work Triangle and recommended
minimum distance between worktops
●
●
Have a good-sized food-preparation area between
the sink and the cooker.
Avoid putting the sink or the cooker in a corner. If
unavoidable, keep them at least 400 mm from the
return wall.
Always have a worktop surface near, or over the
fridge.
Planning the Layout
●
●
Do not place the cooker too far from the sink.
If intending to install an extractor hood that vents
to the outside, try to keep the cooker or hob up
against an exterior wall, or close to one to minimize
ducting above the wall units.
231
overall height from the floor is between 2 m and
2.150 m.
20.3 PLANNING THE LAYOUT
Window
300 mm
411
2.345
Wall
500 mm
600 mm
112
1.2 m rad
Existing
gas
boiler
693
1.780
1.590
630
1.140
900 mm
Base
unit
Walk-in
larder
2.414
unit
2.0 m to 2.150 m
966
1.470
1.036
Figure 20.1 (c) Established ergonomic sizes
Figure 20.1(c): Although the ergonomic features of
kitchen units are standardized to suit manufacturing
purposes, there is room for some adjustment. As illustrated, standard base units, inclusive of worktopthickness, should be about 900 mm high. Using details
obtained from MFI Ltd (whose kitchens I have
installed many times and never faulted) their units can
be lowered to 898 mm or raised to 923 mm to suit a
person’s height and working posture. Such adjustments are done by simply threading or unthreading
the bottom section of the unit’s adjustable legs. The
plinth – that clips onto the front legs – is eventually
reduced in width to suit the first example, but left in
its full width to suit the second. Note that the latter
does not allow for the plinth to be scribed to an
uneven or un-level floor, as is usually necessary. These
overall heights are arrived at as follows: 720 mm base
unit ⫹ 38 mm worktop thickness ⫹ 140 mm minimum size of adjustable legs ⫽ 898 mm minimum;
and 720 mm unit ⫹ 38 mm worktop ⫹ 165 mm maximum width of available plinth ⫽ 923 mm maximum.
However, such adjustments can create a problem
if there is to be a free-standing cooker – instead of a
hob – required to be flush to the worktop surface.
Although modern cookers usually have screwadjustable feet, their minimum and maximum adjustment would need to be checked out. Wall units should
not be less than 460 mm, nor more than about
500 mm above the worktop. To put the cupboard
shelves within easy reach for most people, the ideal
170
813
1.2
Figure 20.2 Rough-drawn measured survey of
kitchen area
Figure 20.2: Although kitchen suppliers like MFI use
computer-aided design software nowadays to produce
plans and 3-dimensional views of a proposed kitchen,
layouts can be produced from initial rough sketches
and line drawings. Even if you have limited technicaldrawing ability, simple scaled cut-outs of the different
sized units can be made and juggled with on a sheet of
graph paper. If necessary, ideas for a kitchen design
can be gained from magazines, kitchen showrooms or
other people’s homes. These ideas are borne in mind
at the sketching and juggling stage. Sometimes all
your ideas work out and an exciting design evolves –
other times compromises have to be made. Apart from
money, the size and shape of the room is the controlling factor in relation to the position of the door(s),
window(s), radiator(s), etc. Therefore, the first stage is
to make a rough freehand sketch and do a careful
measured survey. The sketch shown above is reproduced from an actual kitchen refit completed in recent
years. The original kitchen, apart from a sink and a
walk-in larder, was practically non-existent.
Figure 20.3: Following on from the measuredsurvey sketch, ideas were juggled around and the final
layout drawing evolved and is reproduced here. Note
that this layout highlights practicalities such as the
various small infill pieces required to achieve the
U-shape arrangement of the base units and to infill
Designing and Installing a Fitted Kitchen
631 ⫻ 631 mm
diagonal
wall
unit
3
2.414 m
9
2.345 m
0.411 m
3
10
4
5
Sink
931 ⫻ 931 mm
Carousel
base unit
6
∗
11
0.966 m
Existing
walk-in
larder
12
∗
∗
1.470 m
1.036 m
2
7
8
1
40
13
m
7
1.
Work
Triangle
= 5.370 m
Cooker
1.
2.130 m
232
50
0m
∗ Infill pieces
Welsh dresser
Existing
fridge/
freezer
Purpose-made
1.140 m
0.693 m
Existing radiator
Existing
gas
boiler
1&2
4
5
6&7
8&9
10
11 & 13
12
= 400 & 300 mm base units
= 600 mm 3-drawer base unit
= 800 mm sink unit
= 2 ⫻ 500 mm base units
= 400 & 600 mm wall units
= 290 mm open-end wall unit
= 2 ⫻ 500 mm glass wall units
= 400 mm open wall unit
Figure 20.3 Final design layout of kitchen
the end of the number 11 wall unit. It was decided to
keep the ventilated walk-in larder, which raised
another practical issue. Wall units with glass doors
and base units were to be fixed on the larder wall,
which was of timber studwork and plasterboard. The
base units would be secure enough fixed to this with
modern cavity fixings, but to ensure the security of the
wall units, a 100 mm strip of 12 mm plywood was
fixed to the plasterboard surface, into the studs. This
provided fixings for the metal mounting plates, as
indicated in Figure 20.10. To accommodate the plywood strip, the back-edges of the wall units – that
project beyond the groove for the back panel – had to
be notched out and the suspension brackets had to be
moved back into the units by 12 mm.
20.4 DISMANTLING THE OLD
KITCHEN
If you are replacing an existing kitchen, then obviously
the old one needs to be taken out. In doing this, use a
sensible approach – not a sledge hammer! First,
arrange for any integrated electrical wiring to be disconnected, the hot and cold water supply to be capped
and any gas supply to be turned off and disconnected.
After that, dismantle the fitted units generally in the
reverse order of their assembly, i.e., cornices, pelmets,
plinths, worktops, and so on. To speed things up, lever
parts off with a crow bar instead of unscrewing everything tediously.
Pre-fitting Preparation
233
20.5 PRE-FITTING PREPARATION
If the composition of the walls is unknown to you,
then check this out by tapping or piercing with a
pointed awl, especially in a room not previously designated as a kitchen. Solid plastered walls are generally
not a problem, dry-lined walls can be accommodated,
but – as described in the paragraph under Figure 20.3
above – timber studwork and plasterboard may need
to be overlaid with plywood strips, acting as fixing
grounds. Other preparations are as follows:
‘Chasing’
Figure 20.4 (b) Socket outlets related symmetrically
to tiling
Cable-loops concealed
behind units
Cross-section
Longitudinal section through units
●
Figure 20.4 (a) Hit-and-miss ‘chasing’ above base units
●
●
Figure 20.4(a): Now is the time to upgrade the
electrics and install a new ring main (ring circuit),
using 2.5 mm2 two-core-and-earth cable to provide
adequate double socket outlets above the worktops
and in other places. These include electrical points
for items such as a dishwasher, fridge and washing
machine – and spurred, fused connection-units to
an extractor fan, lighting in glass cabinets and
lighting under the wall units, etc. If the cooker or
hob is to be electric, then a separate circuit using
4 mm2 two-core-and-earth cable must be run from
a cooker control unit, back to a 30 amp fuse or a
32 amp MCB (miniature circuit breaker) in the
consumer unit. Since changes in the electrical regulations came into force in January 2005, all of this
work must now legally be done by a competent
electrician – but ‘chasing’ (channelling) the walls to
conceal the cables, can be tackled to lessen the specialist work (and, hopefully, the cost). As illustrated,
this can be minimized by using a hit-and-miss
technique for the outlets above the worktop, as the
ring-main loops will be concealed within a void at
the back of the cupboards.
Figure 20.4(b): If there is to be tiling on the back
walls above the worktops – which is quite common –
the critical height and lateral position of the socket
●
●
●
●
outlets should be considered. The reasoning for this
is partly to do with the ergonomics of handling the
plugs – which is easier if the plugs are higher – but
mostly to do with the symmetry of tile-joints
related to socket-outlet positioning. Centre-line
heights of outlets should be about 190 mm or more
above the worktop. Being higher avoids clashes
with sugar jars, etc.
Drill through the outer wall and position the sink
waste pipe, left poking through, ready for connection, and run the hot and cold water supplies, left
poking up ready to enter the sink unit. These
15 mm Ø copper pipes should be capped off with
so-called miniature valves. If a gas supply is
required, this should also be installed at this stage.
Any additional or new lighting required in the ceiling, should now be fitted.
Metal mounting boxes should be screwed into each
outlet-recess cut in the walls. Where tiles are to be
fixed, the boxes can protrude by that thickness;
(this should be taken into account from the outset,
to reduce the cutting-depth into the wall). Ovalshaped plastic conduit should be fixed in the cablechases, enabling easier future rewiring to be done.
The conduit should run from a rubber grommet in
the box and be side-fixed in the chases with small,
galvanized clout nails. After the ring-main cabling
has been looped through the plastic conduit, all the
making good of plasterwork can be completed.
The room should now be decorated, the ceilings
finished, the walls and woodwork left ready for the
final coat.
Now clear the room and open the flat packs carefully, starting with the carcases. Line the floor with
the cardboard to create a working area, examine
each item for damage and start assembling the base
units, minus the doors and drawers. (MFI provide
excellent illustrated Assembly and Installation
Guides for their Schreiber and Hygena range.)
234
Designing and Installing a Fitted Kitchen
Attach the adjustable legs to each unit and stand it
in its approximate position, out of the way. Then
assemble the remainder of the base units and set
aside. Assembling carcases can continue if you have
spare room for storage, otherwise assemble and fix
in the order of base units, tower units, wall units,
etc. You are now ready to start fixing.
20.6 FITTING AND FIXING
BASE UNITS
Now to continue with the installation of the kitchen
illustrated in Figure 20.3. In order to set out the position of the socket outlets required above the worktops
in relation to the tiling joints, it was necessary in the
early stages of preparation to mark the exact height of
the worktop around the walls. In this case, the height
was determined by the fact that the existing one-yearold electric cooker was to be reused. Its height of
910 mm was set on the wall as a datum measured up
from its designated position, which was then carefully
levelled and pencil-marked around the three walls as a
continuous reference line.
Figure 20.5 (a) Base-unit cheeks fixed to wall
Figure 20.5(a): With a few exceptions, base units are
fixed to the wall via two small metal brackets supplied
with the units. As illustrated, these are screwed close
to the top of the side-cheeks on the inner back edges.
If the wall surfaces are ‘out of plumb’ or not very
straight in their length, the back edges of the units
may need to be scribed to the irregular shape before
the brackets are fixed. Sometimes, small pieces of thin
packing strategically placed will suffice. Prior checking
with a straightedge and spirit level will confirm
whether this additional work has to be done.
Figure 20.5(b): As illustrated, the only other fixings
required to hold the units are the two-part plastic
Figure 20.5 (b) Base-unit cheeks joined near front with
two plastic connecting screws
connecting screws. These join the front edges of each
unit’s side-cheeks together. The male-and-female plastic screws require 8 mm Ø holes to be drilled through
both cheeks whilst they are held firmly together with a
pair of small G cramps. One fixing is positioned near
the bottom, one near the top, clear of any hinge positions or drawer runners, etc. If necessary – according
to what drill you are using – clamp a piece of flat
waste material on the blind side of the cheeks and
drill into it to avoid ‘spelching’ (breaking the edges
around the exit holes).
Referencing the kitchen layout in Figure 20.3
again, having assembled the base units, screwed on the
legs firmly and adjusted them to the approximate
height, it was time to level up, adjust and scribe them
to the wall. Starting with the left-hand carousel unit,
the five wall-to-wall base units under the window
were fitted (the fifth being another carousel unit in the
right-hand corner against the larder wall). Only minimal scribing was required, mostly to do with the
slightly bell-bottomed protrusion of the lower regions
of traditional plasterwork, affecting the level of the
units at right-angles to the wall. This was easily put
right by planing about 4 mm tapered scribes off the
lower back edges of the cheeks. Before repositioning
each unit, the metal fixing brackets were screwed in
place, as illustrated in Figure 20.5(a). With repeated
reference to the spirit level, final adjustments were
made to each unit’s four adjustable legs. These adjustments also had to relate to the worktop reference line,
which had to be 38 mm (worktop-thickness) above
the top of the units.
Figure 20.5(c): The five base units now ready for
fixing were comprised of a 931 mm carousel unit each
end, a 600 mm 3-drawer unit, a 800 mm sink unit and
a 500 mm drawer-line unit, all adding up to 3.762 m
Cutting, Jointing and Fitting Worktops
(1)
235
Sink-cutout
(2)
(3)
(a)
(1)
Sink-cutout
∗
(3)
(2)
Figure 20.5 (c) * 15 mm laminate-edged infill strip
between each carousel and adjacent unit
(b)
in relation to a room-width of 3.792 m. This meant
that an infill of 30 mm was needed – which was
known and accepted at the design stage. As illustrated
above, this was made up of two 15 mm strips of
melamine, edge-veneered to match the units. These
were screwed to the face-side front of each carousel
cheek and eventually connected to the adjacent units
with the two-part plastic connecting screws supplied
with the units. After marking the walls through the
holes in the fixing brackets, the walls were drilled and
plugged (see chapter 3 on plugging, if necessary), all
the two-part connecting screws were fitted and connected and the units were screwed back to the walls.
Using a similar procedure to that described above,
the remaining base units on the side walls were fitted
and fixed. This comprised a 300 mm drawer-line unit
coming away from the left-hand carousel, finishing
with a similar 400 mm unit up against the cooker.
Only one 500 mm drawer-line unit was needed up
against the right-hand carousel.
Figure 20.6 (a) Worktop (1) shown jointed at each end
is impractical and should be avoided (b) More practical
jointing arrangement
parallel to each other at each end of one length of
worktop, as in illustration (a) above. It is not ideal
from a practical, fitting point of view – especially if a
number of biscuits are to be inserted in the joints.
A better arrangement, shown in illustration (b) and
used in the example kitchen, allows more control in
fitting worktops (2) and (3) separately. Each of these
arrangements requires 1 ⫻ 3 m and 1 ⫻ 4 m worktops. The 4 m length is cut in two for arrangement (a)
and the 3 m length is cut in two for arrangement (b).
Although small gaps between the worktop and the
wall will be mastered by tiles or cladding, it may be
necessary occasionally to scribe to the wall.
Figure 20.7(a): Because worktop (1) in Figure
20.6(b) was butted to the wall at each end, the square
angle of the walls had to be checked and any major
20.7 CUTTING, JOINTING AND
FITTING WORKTOPS
Although the MFI guide-notes list the fitting of worktops after the wall units, I have always preferred to fit
them before, without the restrictive, head-butting
obstruction of the units above. However, once fitted they
should be covered with the thick cardboard from the
packaging before the work on the wall units is started.
Figure 20.6(a)(b): Laminate worktops are usually
3 m long, but some manufacturers can supply 4 m
lengths as well. When fitting around two or more
corners in a kitchen, avoid having connecting joints
Female cut
(1)
Male cut
(2)
Figure 20.7 (a) Routed joint between worktops (1) and
(2), showing biscuit and panel-bolt slots
236
Designing and Installing a Fitted Kitchen
deviation transferred to the worktop prior to cutting.
Cutting can be done with a hardpoint handsaw or
from the underside with a portable circular saw fitted
with a 60 or 80 toothed TCT blade. Because circularsaw teeth revolve upwards towards the front of the
saw’s base, cutting from the underside minimizes
damage to the laminate surface. After being fitted
with a slight tolerance, worktop (1) was then removed
and positioned for routing.
With the location bushes set up on a worktop-jig
such as the Trend Combi 651, illustrated and described
in chapter 2, the jig was G-cramped into position and
the first female joint on the left-hand side was cut. This
had to be done in at least three cuts of increasingdepth to remove the bulk of the waste, before the
finishing cut was made. Using a 1300 watt (minimum
requirement) plunge router with a 12.7 mm (-12⬙) collet
and a 30 mm Ø guide bush, the first three cuts of
varying-depth were run against the tolerance-side
within the oversized guide slot of the jig. This left a
small surplus edge on the joint-side of the jig which
was routed off in one full-depth pass on the fourth
finishing cut. After resetting the jig on the right-hand
side of the worktop, the second female joint was cut in
a similar way and the worktop was put back in position.
Worktop (2) was then sawn to length with an
allowance of about 20 mm for finishing each end. The
jig was then set up and a similar method of routing, as
described above, was used to produce the first male
end. Once routed, the worktop was laid in position
and the quality of the joint carefully checked. If not a
perfectly parallel fit, the jig would need adjusting
before re-cutting the male end again. If the joint was
satisfactory, the worktop could be marked for trimming the length to finish squarely against the cooker.
The jig and router were used again to square this off.
Finally, worktop (3) was cut to a provisional length
and the whole jigging, routing and checking procedure repeated. This time, though – because exposed
right-angled edges can be a dangerous height for
children – the outer corner was removed by using the
male-shaping side of the jig to produce the partlyrounded 45⬚ shape.
Figure 20.7(b): Before removing the worktops to
rout out the underside for the T-shaped recesses
which house the panel bolt-connectors, and to cut the
edge slots for the elliptical-shaped wooden biscuits, a
pencil mark was run around the inner rails and cheeks
of the sink unit to determine the position of the cutout for the sink. Then the worktops were removed
carefully – so as not to damage the routed edges –
turned upside down, the jig set up again and used to
form the bolt recesses. Three or four slots for No.20
size biscuits were cut in each joint with a biscuit
jointer – although, by using a biscuit-jointing cutter,
this could have been done with the router.
Panel-bolt
connector
Figure 20.7 (b) ‘T’ or Bone-shaped recesses routed out
to take panel-bolt connectors
20.7.1 Sink Cut-out
First, the pencilled outline of the inner base unit was
squared up onto the laminate surface and the manufacturer’s cardboard sink-template was related to it to
mark the cut-out. Then the oblong shape was cut out
with a jigsaw, after drilling a small entry hole. I learnt
recently that an alternative trade-practice used nowadays for removing this oblong shape is to use a
portable circular saw. Working from the underside, the
cut-out is marked from the template or sink unit in
relation to the marked outline of the unit. A portable
circular saw (with a fine TCT blade) is set up with a
limited blade-projection to slightly pierce through the
laminate surface. The saw is carefully ‘dropped on’ to
each of the four lines to cut the outline shape.
‘Dropping on’ is a technique for piercing the material in mid area. It can be dangerous and should only
be practised by experienced woodworkers. If attempted,
the back of the saw base should be pivoted against a
temporary batten fixed to the material to prevent a
kickback. It should be appreciated that by working a
circular saw into each vertical corner, the cut-out will
still be held by uncut corners below. This gives an
advantage in stopping the cut-out from falling/breaking out prematurely and damaging the laminate edges.
When the worktop is turned face up, a hardpoint
handsaw is used in the corners to finish the job. Before
the sink is finally fitted, the edges of the cut-out
should be sealed with two or three coats of varnish –
or at least receive a thorough spreading of silicone
sealant.
20.7.2 Final Fixing
Understandably, plumbers usually like to fix the taps
to the sink before it is fixed in position, but some
plumbers also prefer to fix the sink as well as the taps
Fixing the Wall Units
before the worktop is placed and fixed in position. So,
having previously agreed to the plumber’s request, he
was called in before the work proceeded. After the
sink was installed, the long worktop was repositioned
and fixed. This was done by screwing up through the
plastic KD Fixit blocks previously fixed to the inner
top surfaces of the base-unit cheeks – and through
shank holes drilled through the manufacturer’s partlydrilled holes in the front rails.
Before worktops (2) and (3) could be fixed in the
same way as worktop (1), they had to be joined
together with the panel bolt-connectors. (Two per
joint are supplied by MFI, but some fixers prefer three
on 600 mm joints.) Before fixing these, though, the
exposed extreme-ends of each worktop were veneered
with iron-on laminate edge strip and carefully
trimmed off with a Stanley knife and a fine flat file.
With the male end of worktop (2) lined up to the
female recess in worktop (1), but sitting back by about
150 mm, the three or four biscuits were tapped into
the male-end slots. Working speedily now, with the
panel-bolt connectors and a ratchet ring-spanner at
the ready, a good-quality brand of clear silicone
sealant was gunned along the routed female-recess
and spread thinly with a spatula to within about 8 mm
of the laminate surface. Following on quickly, the
coloured jointing compound was then applied to the
untreated 8 mm margin that had been left clear of the
surface edges. (The coloured compound was used like
this because it is not easy to spread and sets quickly;
therefore the less applied, the quicker the assembly
time.) Finally, the joint was brought closely together,
the bolts inserted on the underside and quickly tightened with the ratchet spanner.
During this process, frequent checks were made
regarding the flushness and closeness of the join (sometimes, a slightly fat or thin biscuit can upset the surface flushness. For this reason, some kitchen installers
omit the biscuits completely – although the surfaces can
be checked by putting the joint together dry, with the
biscuits in place, before committing yourself to the final
fit). With the aid of a wooden spatula, the squeezedout compound was scraped off the worktop surface
and cleaned up immediately with the cleaning solution
provided – and any squeezed out droppings inside the
unit were also cleaned up. This jointing procedure was
repeated to join worktops (1) and (3) together before
the final screw fixings were made on the underside.
237
B
A
(a)
(b)
Figure 20.8 (a) Metal mounting-plate; (b) adjustable
suspension-bracket
was time to fix the wall units. These had already been
assembled previously, minus the doors. After cutting
and adapting the cardboard packaging to lay on the
worktops for their protection, horizontal lines were
pencilled around the wall to establish the top of the
units. This equalled the units’ height of 720 mm ⫹
460 mm minimum height above the worktop. The line
also acted as a datum for plotting the critical positions
of the suspension-bracket mounting plates. These
metal plates are fixed to the wall before the unit’s integral suspension brackets are hooked upon them and
adjusted for final position. By turning clockwise or
anti-clockwise (with a non-powered screwdriver only)
screw ‘A’, indicated above, is for vertical adjustment up
or down and screw ‘B’ is for horizontal adjustment
towards the wall or away from it.
Ceiling
31 mm
31 mm
20 mm
2 mm
80 mm
80 mm
Figure 20.9 Positions for mounting plates and vertical
rails (grounds) for corner unit
20.8 FIXING THE WALL UNITS
Figure 20.8(a)(b): As there was no so-called tower
units in the example kitchen used here, which would
have been fixed next to determine the overall height, it
Figure 20.9: Starting with the 631 ⫻ 631 mm diagonal
corner unit, it was first held in position, up against the
datum line, and each side cheek was marked on the
wall, as illustrated. The two metal mounting plates
238
Designing and Installing a Fitted Kitchen
were marked, plugged and screwed at 31 mm down
from the top and 20 mm in from each side. The loose
chipboard rails (supplied), acting as vertical grounds,
were also fixed to the wall at 80 mm from the corner.
The unit was then hung on the mounting plates via
the integral suspension brackets and adjusted vertically
to the datum line and a spirit level before being screwed
back to hold its position. Finally, the unit was screwed
to the chipboard grounds with the 8 ⫻ 16 mm flangeheaded screws (4 each side) supplied.
The two wall units on the left of the corner unit, a
600 mm 2-door and a 400 mm single door, were fixed
in a similar way. Each was fitted to a pair of metal
mounting-plates positioned at 31 mm down from the
datum and 20 mm in from each side as before – but
instead of loose vertical rails, these units had a fitted
horizontal rail, positioned low down behind the back
panel. This needed to be drilled twice for final fixing to
the wall with the 2-14⬙ (57 mm) ⫻ 8 CSK screws supplied.
The final unit on this side of the kitchen was the
290 mm open-end display unit on the right of the corner
wall-unit. Because of its solid construction, mounting
plates and suspension brackets were not needed this
time. It was simply screwed to the wall at the top and
bottom with two 2-14⬙ ⫻ 8 CSK screws supplied – and
attached to the corner unit with four 1-14⬙(32 mm) ⫻ 6
CSK screws supplied. These final four screws were
concealed by being drilled and fixed from inside the
cupboard unit, near the hinge positions. The exposed
wall fixings were concealed with plastic KD cover caps.
The side-cheek attachment of the display unit near
the hinge positions was also required on the other
adjoining cheeks of the units. These fixings, though,
were made with two-part plastic connecting screws –
similar to the connections made on the base units, illustrated in Figure 20.5(b). Generally speaking, because
of slight irregularities in the shape of most wall surfaces,
it is better to make the cheek-connections – with the
aid of a pair of G-cramps – before the units are screwed
back to the wall through their lower, concealed rails.
Figure 20.10: On the other side of the kitchen now,
against the larder wall, the three remaining wall units
were fixed by using the same methods and techniques
described above. However, to keep the symmetrical
alignment of door-positions above in line with the
door and drawer-positions below, a 31 mm infill was
required against the left-hand wall, as indicated in the
kitchen layout of Figure 20.3. This came about
because the end of the 931 mm carousel base unit was
31 mm wider than the end of the 400 mm wall unit
that had been joined to the 500 mm unit with glassdoors. Although infill pieces of limited size can be
attached to the end of the unit, Figure 20.10 indicates
an alternative method of fixing infill pieces to the wall.
Ceiling
B
D
A
C
Figure 20.10 31 mm infill strip ‘A’ fixed to left-hand wall.
‘B’ and ‘C’ infill strips are optional. ‘D’ ⫽ 100 mm ⫻
12 mm plywood strip fixed to stud partition to provide
fixings for the metal mounting-plates
20.9 ADDING FINISHING
ITEMS
Apart from finalizing the plumbing, electrics and
decoration, the remaining finishing jobs in a logical
sequence are: Fix manufactured backboard-splashbacks,
or tiles, etc, around worktop-walls; Fix pelmets under
wall-units (optional, but necessary if under-cupboard
striplights are to be installed); Fix cornices above wallunits (also optional); Fix gallery rails to display units
(if such units have been fitted); Scribe and reduce
plinths to fit between underside of base units and the
floor, minus an additional 2 mm to accommodate the
plastic, plinth sealer-strip. Fit and fix plinths as per
MFI guide notes; If G-Met or Cushion-close drawers
have been chosen, fix the drawer-fronts and fit the
drawers; If Standard drawer-box drawers are being
used, assemble these and fit them; Fix the hinges to
the doors and hang the doors; After all drawers and
doors have been fitted and aligned carefully, and not
before, fit the dummy drawer fronts where required, as
per the guide notes; Finally, remove the backing adhesive from the small plastic buffers and fit them to all
doors and drawers – and fit the following where
required: hinge-hole cover caps, hinge-plate hole
cover caps, wall-fixing screw cover caps, 8 mm-hole
cover caps and cam cover caps.
21
Site Levelling and Setting Out
21.1 INTRODUCTION
Setting out the position of new buildings in relation to
the required levels is a very responsible job and it must
be borne in mind that mistakes can be costly. Apart
from the upset to client and contractor, the local authorities can be unforgiving. Disputes over this can hold up a
contract indefinitely and it is not unheard of for a
partly-formed structure to be demolished and re-sited in
the correct position. On large sites – especially those
that involve a complexity of detail and the layout of
roads and buildings – site engineers or surveyors are
usually responsible for setting out and establishing the
various levels. However, on small to medium-sized projects, such as the building of a few dwellings or a
detached garage, the site levelling and setting out is usually done by the builder. This chapter covers the basic
information required to set out the foundations, walls,
drain-levels and site levels of a detached dwelling.
established as the mean sea-level at Newlyn in Cornwall.
The value of OBM readings are recorded on Ordnance
Survey maps related to block plans of built-up areas and
can usually be viewed or obtained from a local authority’s Building Control Department. Where there are no
OBMs in the vicinity of a building site, an alternative,
reliable datum – such as a stone step, plinth of a nearby
building, or a manhole cover in the road – must be used.
21.2.1 Levelling Equipment
Required – The Level
21.2 ESTABLISHING A
DATUM LEVEL
Figure 21.1 Ordnance Bench Mark (OBM)
Figure 21.1: It is essential in all site-levelling operations
that the various levels required should have reference to
a fixed datum. Wherever possible this should be the
Ordnance Bench Mark (OBM), which is a chiselled-out
arrow head with a horizontal recess above it, as illustrated
above. OBMs are carved in stone blocks, usually found
set in the walls of public buildings and churches. The
inverted horizontal centre line over the arrow is a
reference height set above the Ordnance datum by the
Ordnance surveyors. The original Ordnance datum was
Figure 21.2 A typical automatic level
Figure 21.2: There are a variety of levelling instruments
available and ranking high among these are the modified and improved versions of the popular traditional
dumpy level. These instruments include the quickset,
precise, and automatic levels. The automatic level represented above, operates by means of integral selflevelling glass prisms. Once the instrument has been
attached to the tripod and levelled by means of a circular centre bubble, it is ready to be used. The principle
upon which it works is that the observer’s view of
the horizontal hairline – that bisects the vertical
Site Levelling and Setting Out
hairline – across the lens establishes a theoretical horizontal plane, encompassing the whole site when the
head of the instrument is pivoted through a 360⬚ circle. This theoretical plane is referred to as the height of
collimation, from which various levels can be measured
and/or established. These levels are taken from a measuring rod known as a levelling staff.
21.2.2 The Levelling Staff
‘E’ staff
OBM
‘E’ staff
Collimation
height = 49.320
I.S.
2.210
B.S.
1.320
48.000 (48 m)
240
F.S.
1.660
‘E’ staff
TBM
or
Datum
1
2
Mean sea-level at
Newlyn, Cornwall
1 : Drain invert = R.L.47.110
2 : Trench-fill foundation = R.L.47.660
Figure 21.4 Graphic example of terms used in levelling
Figure 21.3 The ‘E’ staff
Figure 21.3: Metric staffs with five telescopic sections
for easy carrying and use, are now available in aluminium or fibreglass. They can be extended to 5 m
from a closed length of 1.265 m. The British Standard
model indicated here is often referred to as the ‘E’
staff, for obvious reasons. Each graduated metre is
marked with alternating black and red printing on a
white background. Basically, the letters ‘E’ and the
entire staff are divided into centimetres by virtue of
each red or black square and each white space between
the coloured squares equalling 10 mm. Thereby each
‘E’ has a vertical-value of 50 mm and the coloured
squares and white spaces between each ‘E’ also equal
50 mm. A numbered value is printed at the bottom of
each ‘E’, which is thereby expressing incremental
readings of a decimetre (100 mm). Readings of less
than 10 mm are estimated and can be quite accurate
after a little practice. Clip-on staff-plumbing bubbles
are available and advisable.
21.2.3 Terms Used in Levelling
Collimation Height: The height of a level’s theoretical
viewing plane above the original Ordnance datum established at Newlyn in Cornwall.
Backsight (B.S.): The first staff-reading taken from
an instrument, usually on the datum.
Datum: A solid and reliable fixed point of initial
reference, such as an OBM or a manhole-cover in
the road.
Foresight (F.S.): The last staff-reading before an
instrument is repositioned.
Intermediate sight (I.S.): All readings taken other
than Backsight and Foresight.
Ordnance Bench Mark (OBM): As described above.
Temporary Bench Mark (TBM): This is a temporary
datum transferred from the OBM and set up on site at a
reduced level – or to the same level as any alternative
datum used, such as a manhole-cover in the road – from
which the various site levels are set up more conveniently. The datum peg, either a 20 mm Ø steel bar, or a
50 ⫻ 50 mm wooden stake, is usually set in the ground,
encased in concrete. For protection, it should be strategically positioned to the front-side boundary of the
site and have a confined fence-like guard built
around it.
Reduced Level (R.L): Any calculated level position
above the original Ordnance datum, as illustrated in
Figure 21.4.
21.3 SETTING OUT THE
SHAPE AND POSITION OF
THE BUILDING
21.3.1 Setting-out Equipment
Required – Setting-out pegs
Figure 21.5(a): Setting-out pegs are usually of 600 mm
length and made from 50 ⫻ 50 mm sawn softwood,
Setting Out the Shape and Position of the Building
any position along the trench, whilst another person
sights across the two relevant profiles to see whether the
top of the rod indicates that the trench levels or foundation pegs are too high, too low or correct. Traditionally,
the rod was made from good quality prepared softwood
of about ex 75 ⫻ 25 mm section. The cross piece was
usually jointed to the rod with a tee halving.
Saw cuts in profile board
to take ranging lines
Trenchfill
foundation
(a)
(b)
(c)
241
(d)
Figure 21.5 (a) Setting-out peg; (b) profile-stake; (c)
profile board set up to give lateral position of foundationtrench and brickwork; (d) a boning rod
pointed at one end to enable them to be driven into
the ground. The upper third should be painted with
white emulsion for easy recognition. If preferred, pegs
can be bought ready-made nowadays, with pyramidal
or conical points.
21.3.2 Stakes
Figure 21.5(b): These are similar to setting-out pegs,
but they are not painted and are about 900 mm long.
They are driven into the ground in pairs and a profile
board is nailed to their upper faces.
21.3.3 Profiles
Figure 21.5(c): These consist of ex 150 or 100 mm ⫻
25 mm boards nailed horizontally across a pair of
stakes driven into the ground. (Corner profiles with
three stakes were used originally for hand-digging, but
unless using unreasonably long profile boards, come too
near to the trenches and inhibit the mechanical digger.)
There are two uses for profiles. 1) They can be set up –
well clear of the intended trench lines – without any
regard to being perfectly level and used for setting out
the lateral position of the brick walls and the foundations. This involves marking the wall thickness and
the foundation width on the board’s face, as illustrated, and highlighting these marks with nails or saw
cuts; Or, 2) if the tops of the profile boards (of which
there may be at least eight) are set up level in themselves and in relation to each other, they can be used
with a boning rod for sighting the levels of trench- and
foundation-depths.
21.3.4 Boning Rods
Figure 21.5(d): As illustrated, these resemble a ‘T’ shape
and are made to varying calculated lengths according to
the reduced level required. The simple but effective
technique requires one person to hold the boning rod at
21.3.5 Surveying/Measuring Tapes
Fibreglass tape rules for setting out are now very popular, although traditional steel tapes with an improved
finish are still available. The steel is either coated with
white polyester and the printing protected with an
additional top coat, or – for heavy-duty work – the steel
is coated with yellow nylon and the printing protected
with an additional coat. Tapes of 10, 20, 30 or 50 m are
available, all with loop and claw ends and a fold-away
rewinding handle. A sturdy, pocket tape-rule, such as
the Stanley Powerlock® rule, 8 m long with a 25 mm
wide blade, will also be required in the setting out.
21.3.6 Optical Squaring Instruments
Optical instruments such as digital theodolites, with
an integral laser-plummet facility that emits a vertical
beam from its tripod position, down onto the corner
setting-out peg, can be used to establish 90⬚ right
angles required at foundation level – but they are
extremely expensive for use on small to medium-sized
sites. However, less expensive laser squares are available. Also, when the longest side of a right-angle in
the setting out does not exceed about 20 m, the angle
can be set out by using either a simple method of
geometry or a method of calculation. Practical techniques for setting out right angles reliably by these
methods are given elsewhere.
21.3.7 Ranging Lines
Ranging lines for initial setting out can be obtained in
50 m and 100 m reels of 2.5 mm Ø braided nylon,
coloured orange or yellow for high visibility.
21.3.8 Establishing the Building Line
The first essential operation in setting out the position
of the building is to establish the building line (sometimes referred to as the frontage line). As the term suggests, this line determines the outer wall-face of the
building and is usually given on the site plan as a parallel measurement from the theoretical centre line of an
existing or proposed road in front of the property.
Building-line positions are determined initially by
the local authority, so it is imperative that they are
242
Site Levelling and Setting Out
Existing
dwelling
Proposed
new build
driven into the pegs to determine exact positioning
and are left protruding to hold a ranging line. The
next step is to set out a right angle.
Existing
dwelling
6.2 m
21.3.10 Forming a Right Angle
Woodlea
road
Figure 21.6 Building line related to existing properties
and/or to the centre line of the road
12
13
5
adhered to. When a property is being built in between
two existing dwellings, as illustrated, the building line
can often be established by simply fixing a taut line to
the wall-face on each side.
Alternatively, two setting-out pegs – numbered (1)
and (2) in Figure 21.7 – are used to fix the position.
They are driven into the ground and left protruding
by about 100 mm on each side of the site, well clear of
the flank-wall positions. Their centres are set to the
given dimension of the building line from the centre of
the road. After finally checking the embedded position
of the pegs to the centre of the road again, 65 or 75 mm
round-head wire nails are driven-in to correct any
slight lateral deviation, with their heads left protruding
by about 25 mm to hold a ranging line.
21.3.9 Setting Out from the
Building Line
(5)
(7)
(6)
(B)
a
c
Building line
b
(1)
(3)
(A)
(4)
(2)
Figure 21.7 Two methods of establishing a right angle
from the building line
Figure 21.7: After straining and tying a ranging line to
the nail-heads of pegs (1) and (2), peg number (3) is
measured in from the left-hand side boundary and
driven-in centrally to the line to establish the corner
(quoin) of the flank wall. The overall width of the
building is then measured from this and peg number
(4), illustrated, is driven-in. As before, wire nails are
4
(a)
3
(b)
5
Figure 21.8 (a) 42 ⫹ 32 ⫽ 52; (b) 122 ⫹ 52 ⫽ 132
Figures 21.7 and 21.8(a)(b): The right angle to form
the first flank wall can be made by using either a
method of calculation, illustrated in Figure 21.8(c)
and described below; a simple method of geometry
such as the 3:4:5 method illustrated above at (a), or
the equally simple 5:12:13 method illustrated at (b).
These two ancient geometric formulas that preceded
Pythagoras’ theorem, enable right-angled triangles to
be formed with integral sides, i.e, sides which can be
measured in whole numbers or equal units. Providing
the units remain equal and are set to the prescribed
ratio, right angles of various sizes can be formed easily
by changing the value of the unit.
When using either of these methods, choose a size
of unit that will form as large a triangle as possible in
relation to the setting out. For example, a 1.5 m unit
to a 3:4:5 ratio ⫽ 3 ⫻ 1.5 ⫽ 4.5 m base line,
4 ⫻ 1.5 ⫽ 6 m side line and 5 ⫻ 1.5 ⫽ 7.5 m
hypotenuse. This is indicated in Figure 21.7, where
peg (B) is set up to a 3:4:5 triangle from pegs (3) and
(A). Alternatively, the whole base line between pegs
(3) and (4) in Figure 21.7 can be divided to provide
equal units. The result of such a method is indicated
between pegs (3), (4) and (5). The advantage with this
is that the ranging line between pegs (3) and (5) is
long enough to set up the rear of the building at peg
(6). The setting up of peg (7), to complete the outline
of the building, can either be set up in a similar way to
peg (6), or its position can be determined by parallel
measurements. Either way, once the four main pegs
are established, diagonals (3) to (7) and (4) to (6)
should be measured for equality to confirm that the
setting out is truly square.
Setting Out the Shape and Position of the Building
Method of Calculation
c2
a2
a
c
b
b2
243
pin-point positioning of peg (5), peg (6), or peg (B) is
critical. It is usually done with two tape rules, each
looped over the nails in the two relevant building-line
pegs and strained over the site to meet at their intersecting apex point, as in Figure 21.9(a). Initially, this will be
done to establish the position for the peg, then repeated
to pin-point the nail position. Intermediate support, such
as bricks-on-edge (if the pegs are about 100 mm above
ground), should be used under the tape if there is too
much sagging. If only one tape rule is available, a brickon-edge can be set up at the apex point and adjusted for
position after separate measurements are made to the
base pegs and marked on the brick. The apex peg is then
related to this mark and driven-in. To pin-point the apex
with a single rule, bisecting arcs can be made on the peg,
∗ If using only
one tape rule, make
intersecting arcs with
a pencil held against the tape
Figure 21.8 (c) Pythagoras’ theorem: a2 ⫹ b2 ⫽ c2
Figure 21.8(c): Finally, if preferred, the right angle can
be formed by treating pegs (3), (4) and (6) as a triangle
and using a method of calculation known as Pythagoras’
theorem, where the square on the hypotenuse c of a
right-angled triangle is equal to the sum of the squares
on the other two sides a and b, i.e.
∗
Peg(B), (5) or (6)
a2 ⫹ b2 ⫽ c2
Thereby it is possible to find the length of the
hypotenuse if the length of sides a and b are known.
Once the sum of the square on the hypotenuse
(represented by the superscript ‘2’ after the number,
meaning that the number is to be multiplied by itself )
has been worked out, the square root of that sum will
give the length of the hypotenuse c, i.e.
c2 ⫽ c
With reference to Figure 21.7 again, if the width of
the building was 8.750 m between pegs (3) and (4)
and the depth was, say 12.500 m between pegs (3) and
(6), to find the length of the hypotenuse, c thus
enabling peg (6) to be squared to peg (3), the following sum would be used:
To peg (3)
To pegs (A) or (4)
Figure 21.9 (a) Squaring technique with tape rules
as indicated in the Figure above. If ever a peg is found to
be slightly out of position when pin-pointing, rather
than move it, drive another peg in alongside.
Figure 21.9(b): When looping the end of a tape rule
over the centralized nail in a peg, it should be realized
that about three or four millimetres are gained or lost
every time you read or set a measurement. This is
partly due to the inaccuracy of most end-loops and to
c 2 ⫽ 8.750 2 ⫹ 12.500 2
(c 2 ⫽ 8.750 ⫻ 8.750 ⫹ 12.500 ⫻ 12.500)
c 2 ⫽ 76.562 ⫹ 156.25
c 2 ⫽ 232.812
c ⫽
232.812 (c ⫽ the square root of 232.812)
c ⫽ 15.258 m
Peg (3),
(4) or (A)
21.3.11 Squaring Technique
Figure 21.9(a): Whatever method of triangulation is
used from the three variations given above, the precise
Figure 21.9 (b) Tape rule looped over RH wire nail
244
Site Levelling and Setting Out
the fact that half the nail’s shank-diameter is over-sailing the centre point. With this in mind, the allowance
that needs to be added to every looped measurement –
or taken off of every looped reading can be worked out.
75 mm round-head wire nails have a 3.75 mm Ø, so
nearly 2 mm is lost or gained here. Now check the
tape with another rule and add any loop inaccuracy
to this and you have your ⫹ or ⫺ allowance.
21.3.12 Positioning and Marking the
Profile Boards
(1)
(9)
(11)
(5)
(12)
(8)
(2)
Building line
setting-out pegs and lines (about 100 mm), as illustrated, it can be seen how the face-of-brickwork lines
are transferred to the profiles. However, it is a delicate
task and care should be taken in steadying a spirit
level against the face of the board and adjusting it
until a plumb position coincides with the ranging line
below. Once marked with a sharp carpenter’s pencil
and squared onto the top edge, this acts as a datum
from which the wall thickness and foundation width
are marked. These are established by shallow saw cuts
or by fixing wire nails into the top edge. Note that as
indicated in Figure 21.10(a) and (b), additional setting-out pegs are required at points (8) to (12) to
allow the ranging lines to be extended for marking the
profile boards.
21.3.13
Sloping Sites
(x)
(10)
Figure 21.10 (a) Positioning of profiles, showing
additional setting-out pegs (8) to (12)
(y)
Figure 21.10(a): As mentioned previously and illustrated above, the profiles for lateral positioning of the
walls and foundation-trenches must be kept well back
to allow access for the mechanical digger. The 900 mm
stakes are driven-in to about half their length and the
boards are fixed reasonably level with 50 or 65 mm
round head wire nails. The boards should be fixed on
the side of the stakes that takes the strain when the
ranging lines are stretched out.
Peg (11)
Peg (1)
(a)
x
2
x
2
(b)
Figure 21.11 (a) Horizontal measurements on a sloping
site; (b) stepped measurements via setting-out pegs and a
spirit level
Peg (3)
Figure 21.10 (b) Levelling up to profiles from
setting-out lines
Figure 21.10(b): Bearing in mind the relative heights
of the profile boards (about 450 mm) above the
Figure 21.11(a)(b): Finally, sloping sites must be mentioned. Although these will not affect the triangulation
methods of setting out a right angle, they can affect the
horizontal measurements of walls. As illustrated, the
given dimension of a wall (X) can be considerably
reduced geometrically to produce (Y) if measured down
a slope. To combat this, stepped measurements would be
required at ground level, as indicated.
Appendix: Glossary of Terms
The terms and other technical names listed here for explanation, are relevant to those used in this book only – not to
the industry as a whole. For continuity, some terms are
explained in the appropriate chapter and may or may not
be repeated here.
Aggregate: Stone, flint and finer particles used in concrete.
Apron lining: A horizontal board, covering the roughsawn vertical face of a trimmer or trimming joist in a
stairwell.
Architrave: A plain or fancy moulding, mitred and fixed
around the face-edges of door openings, to add a visual
finish and to cover the joint between plaster(board) and
door frame or lining.
Arris, arrises: The sharp corner edges on timber or other
material.
Ashlaring or ashlars: Vertical timber studs fixed in an
attic room from floor to rafters, to partition off the lower,
acute angle of the roof slope.
Balusters: Lathe-turned wooden posts, fixed between the
handrail and string capping or handrail and landing nosing,
as part of the balustrade of a staircase.
Baluster sticks: As above, but only square posts with no
turning.
Balustrade: The barrier or guarding at the open side of a
staircase or landing, comprising newel posts, handrail and
balusters (spindles).
Bare-faced tenon: A tenon with only one shoulder.
Bearer: A timber batten, usually ex. 50 ⫻ 25 mm, that supports a shelf.
Bearing: The point of support for a beam, lintel or joist.
Bed, bedding or bed joint: A controlled thickness of
mortar – usually 10 mm – beneath timber plates, bricks
and blocks.
Birdsmouth: A vee-shaped notch in timber, that is thought
to represent a bird’s mouth in appearance.
Bits: Parallel-shank and square-taper shank tools that fit
a power drill and/or a carpenter’s ratchet brace for
drilling and countersinking.
Block partitions: Partition walls built of aerated insulation blocks, usually measuring 440 mm long ⫻ 215 mm
high ⫻ 100 mm thick.
Bow: A segmental-shaped warp in the length of a board,
springing from the wide face of the material.
Boxwood: A yellow-coloured hardwood with close,
dense grain – still used in the manufacture of four-fold
rules and chisel handles, to a limited extent.
Brace: 1. A diagonal support. 2. A tool for holding and
revolving a variety of drill bits.
Brad head: The head of a nail (oval brad) or awl
(bradawl) whose shape is scolloped from the round or
oval to a flat point.
Breather membrane: Water-resistant, breathable (vapour
permeable) fabric material manufactured from high-density
polyethylene. Available in 50 m rolls, 1.5 m and 1 m wide.
Used in recent years for protecting roofs and timber-framed
walls from external elements, whilst improving the energy
efficiency and thermal targets in a building by making ventilation unnecessary in both cold and warm-decked constructions.
Bullnose step: A step at the bottom of a flight of steps,
projecting past the newel post, with a quadrant-shaped
(quarter of a circle) shaped end.
Burr: A sharp metal edge in the form of a lip, projecting
from the true arris of the metal.
Butt-joint: A square side-to-side, end-to-end or end-to-side
abutment in timber, without any overlapping.
Casement: Hinged or fixed sash windows in a casement
frame.
Centimetre: One hundredth of a metre, i.e. ten millimetres
(10 mm).
Chamfer: An equal bevel (45° ⫻ 45°) removed from the
arrises of bearers or slatted shelves.
Chase, chased, chasing: Rough channels or grooves cut in
walls or concrete floors to accommodate pipes, conduits or
cables; or cut in the face of mortar beds to take the topturned edge of apron flashings.
Chord: A reference to trussed-rafter rafters (top chord)
and trussed-rafter ceiling-joist ties (bottom chord).
Chuck: The jaws of a drill or brace.
Cladding: The clothing of a structure in the form of a relatively thin outer skin, such as horizontal weather-boarding
or tiles.
Cleats: Short boards or battens, usually fixed across the
grain of other boards to give laminated support to the join.
246
Appendix: Glossary of Terms
Clench-nailed: Two pieces of cross-grained timber held
together by nails with about 6–10 mm of projecting point
bent over and flattened on the timber, in the direction of
the grain for a visual finish, or across the grain for extra
strength.
Coach bolt: This has a thread, nut and washer at one end
and a dome-shaped head and partly square shank at the
other. The square portion of shank is hammered into the
round hole to stop the bolt turning while being tightened.
Common brickwork: Rough brickwork or brickwork built
with cheaper non-face bricks, to be plastered or covered.
Concave: Shaped like the inside of a sphere.
Concentric: Sharing the same centre point.
Conduit: A metal pipe for housing electrical
cables; although nowadays plastic and fibre tubes are
mostly used.
Convex: Shaped like the outside of a sphere.
Corbel or corbelling: A structural projection from the
face of a wall in the form of stone, concrete or stepped
brickwork, to act as a bearing for wall plates and purlins,
etc.; straight or hooked metal corbel plates, being the
forerunner of modern joist hangers, were used at about
1 m centres, projecting from the face of a wall, to support
suspended wall plates.
Course: One rise of bricks or blocks laid in a row.
Cramp: 1. Sash cramp – a tightening device for holding
framed timber components together under pressure, usually while being glued. 2. Frame cramp or tie – a galvanized steel bracket holding-device, fixed to the sides of
frames and bedded in the mortar joint.
Cross-halving: A half-lap joint between crossed timbers.
Cup or cupping: Concave or convex distortion across the
face of a board, usually caused by the board’s face being
tangential to the growth rings.
Datum: A fixed and reliable reference point from which all
levels or measurements are taken, to avoid cumulative
errors.
Decimetre: One tenth of a metre, i.e. 100 millimetres
(100 mm).
Dihedral angle: The angle produced between two surfaces, or geometric planes, at the point where they meet.
For example, two vertical surfaces meeting at rightangles to each other, produce a dihedral angle of 90°, but
incline the surfaces from their vertical state, to represent
a hip or valley formation, and the dihedral angle thus
produced is different, according to the degree of
inclination.
Door joint: The necessary gap of 2–3 mm around the
edges of a door for opening clearances.
Dovetail key: The locking effect of a dovetail, or nails
driven in to form a dovetail shape.
Dowel: A round wooden (usually hardwood) or
metal pin.
Draw-bore pin: A front-tapered wooden dowel, driven
into an offset hole drilled (separately) through a mortice
and tenon joint, to pull up the shoulder-fit and permanently reinforce the joint.
Easing: 1. Removing shavings from an edge to achieve a
better fit. 2. Concave and convex shaping of the top
edges of stair strings (especially on the two right-angled
wall strings containing tapered steps in a quarter-space
turn).
Eaves: The lowest edge of a roof, which usually overhangs the structure from as little as the fascia-board
thickness up to about 450 mm, where rainwater drainage
is effected via a system of guttering and downpipes.
Eccentric point: The bent portion of a trammel-head
pin, which causes the axis (centre) of the pin to move,
when rotated, in an eccentric orbit, even though the pinpointed position remains concentric. This allows fine
adjustments to be made to the trammel distance without
altering the trammel head itself.
Facework or face brickwork: Good quality face bricks,
well-laid to give a finished appearance to the face of
walls.
Fair-faced brickwork: Common brickwork, roughly
pointed and bagged (rubbed) over with an old sack.
Fillet: A narrow strip of wood, rectangular or triangular
in section, usually fixed between the angle of two surfaces, as a covermould.
Firring: Building up the edges of joists, with timber
strips which may be parallel or wedge-shaped, to achieve
a level, a sloping or a higher surface when boarded or
covered in sheet material.
Flange: The bottom or top surface of a steel I beam or
channel section.
Flashing: A lead or felt apron that covers various roof
junctions.
Fletton: An extensively used common brick, named after
a village near Peterborough and made from the clay of
that neighbourhood.
Floating: see Rendering.
Flush: A flat surface, such as a flush door, or in the form
of two or more components or pieces of timber being
level with each other.
Gablet: The triangular end of a roof, known as a gablet
when separated from the gable wall below, as in a gambrel roof.
Glue blocks: Short, triangular-shaped blocks, glued –
and sometimes pinned – to the inside angles of steps in a
wooden staircase and other joinery constructions.
Going: The horizontal distance, in the direction of flight,
of one step or of all the steps (total going) of a staircase.
Grain: The cellular structure and arrangement of fibres,
running lengthwise through the timber.
Green brickwork: Freshly laid or recently laid brickwork,
not fully set.
Groove: A channel shape sunk into the face or edge of
timber or other material.
Grounds: Sawn or planed (prepared) battens, which may
be preservative-treated, used to create a true and receptive fixing surface.
Gullet: The lower area of the space between saw teeth.
Appendix: Glossary of Terms
Gusset plate: A triangular-shaped metal (or timber; usually plywood) joint connector.
Half-brick-thick wall: A stretcher-bond wall, where
bricks are laid end-to-end only, in one thickness of brick.
Hardcore: Broken brick and hard rubble used as a substrata for concrete oversites.
Hardwood: A commercial description for the timber
used in industry, which has been converted from broadleaved, usually deciduous trees, belonging to a botanical
group known as angiosperms. Occasionally, the term
hardwood is contradictory to the actual density and
weight of a particular species. For example, balsa wood is
a hardwood which is of a lighter weight and density than
most softwoods.
Heel: The back, lower portion of a saw or plane.
Hone: Sharpen.
Housing: A trench or groove usually cut across the
timber.
Inner skin: The wall built on the dwelling-side of a
cavity wall, usually constructed in blockwork.
Inner string or wall string: One of the two long, deep
boards that house the steps at the side of a staircase,
being on the side against the wall.
In situ concrete: Concrete units or structures cast in their
actual and final location, controlled by in situ formwork
(timber shuttering).
Jamb: The name given to the side of a door frame or
window frame.
Joists: Structural timbers that make up the skeleton
framework in timber floors, ceilings and flat roofs.
Kerf: The cut made by a saw during its progress across
the material.
Knots: Roots of a tree’s branches, sliced through during
timber conversion. Healthy-looking knots are known as
live knots, and those with a black ring around them are
likely to fall out and are known as dead knots.
Knotting: Shellac used for sealing knots (to stop them
bleeding or exuding resin) prior to priming. Shellac is
derived from an incrustation formed by lac insects on the
trees in India and nearby regions.
Lag or lagged: Wrapped or covered with insulation
material.
Landing nosing: The narrow, projecting board, equal in
thickness and shape to the front-edge of a tread board, that
is fixed on all top edges of the landing stairwell. It is often
rebated on the underside to meet a reduced-thickness of
floor material.
Lignum vitae: Dark brown, black-streaked hardwood
with extremely close grain. It is very hard and dense,
about twice the weight of British elm, grown in the
West Indies and tropical America.
Lintel: A concrete or metal beam over door or window
openings.
247
Mitre: Usually a 45° bisection of a right-angled formation of timber (or other material) members – but the
bisection of angles other than 90° is still referred to as
mitring.
Muzzle velocity: The speed of a nail in the barrel of a
cartridge tool.
Newel posts: Plain or lathe-turned posts in a staircase,
usually morticed and jointed to the outer string and the
handrail tenons and attached to the floor at the lower
end and to the landing trimmer at the other. The newel
posts assist in creating good anchorage of the staircase at
both ends, as well as providing stability and strength to
the remainder of the balustrade.
Noggings: Short timber struts, usually between studs or
joists and rafters.
Normal: The geometrical reference to a line or plane at
right-angles to another, especially in the case of a line
radiating from the centre of a circle, in relation to a
right-angled tangent on the outside.
Nosing: The projecting front-edge of a tread board past
the face of the riser, reckoned to be not more than the
tread’s thickness.
Open-riser stairs: Stairs without riser boards.
Outer skin: The wall built on the external side of a
cavity wall.
Outer string: One of the two long, deep boards that house
the steps at the open side of a staircase, away from the
wall.
Oversite: An in situ concrete slab of 100 mm minimum
thickness, laid over hardcore on the ground as part of the
structure of this type of ground floor.
Paring: Chiselling – usually across the grain.
Pellets: Cork-shaped plugs for patching counterbored
holes when involved in screwing and pelleting.
Perpends: Perpendicular cross-joints in brickwork or
masonry.
Pilot hole: A small hole made with a twist drill or
bradawl to take the wormed thread of a screw.
Pin or pinned: Fixed with wooden-dowel pins, but more
commonly the reference is to fixing with nails or panel pins.
Pinch rod: A gauge batten for checking internal distances for parallel.
Pitch: 1. The angle of inclination to the horizontal of a
roof or staircase. 2. Repetitive, equal spacing of the tips
or points of saw teeth or other equally spaced objects.
Plant: Equipment.
Planted mould or stop: Separate mouldings or door
stops, pinned or fixed by nails to the base material.
Plate: 1. A horizontal timber that holds the ends of vertical
or inclined timbers in a state of alignment and framed
spacing, as in the case of roof wall-plates and stud-partition
sill plates and head plates. 2. Metal components such as
striking plates for latches and letter plates.
Plumb or plumbing: Checking or setting up work in a
true, vertical position.
248
Appendix: Glossary of Terms
Plumb cut: The vertical face of a cut angle.
Pocket screwing: Screws which are angled or skewscrewed into shallow niches and shank holes drilled at an
angle through the (usually) hidden face of the timber
being fixed – an example being the top riser and nosing
piece of a stair.
Precast concrete: Concrete units cast in special mould
boxes in a factory or on site, but not cast in their actual
and final location.
Primed: Painted with the first coat of paint (priming)
after being knotted.
Profile: 1. A horizontal board attached to stakes or pegs
driven in the ground, across the line of an intended foundation strip – one at each end, set well clear of the
digging area, has saw cuts or nails in the top edge of the
board to mark the foundation and wall positions. When
initially digging or building, ranging lines are set up
across the boards to establish the required positions. In
the case of mechanical digging, a thin line of sand is
trickled vertically beneath the lines to mark the trench
position, then the lines are removed and reinstated later
when the building work is to be started. 2. Any object or
structure acting as a template in guiding the shape of
something being made or built.
Quadrant: 1. A right-angled sector shape, equalling a
quarter of a circle. 2. A small, wooden bead of this shape.
Rebate: A return or inverted right-angle removed from
the edge of a piece of wood or other material.
Rendering and/or floating coats: Successive coats
of coarse plaster built up to an even and true surface
for skimming.
Resin bonded: This is usually a reference to the crosslaminates of plywood having been bonded (glued) with
synthetic resins. According to the type of resin used, the
plywood may be referred to as moisture resistant (MR),
boil resistant (BR), or – better still – weather and boil
proof (WBP).
Retaining wall: A wall built to retain high-level ground
on a split-level site.
Reveals: The narrow, return edges or sides of an opening
in a wall.
Rise: The vertical distance of one step or of all the steps
(total rise) of a staircase.
Riser: The vertical face or board of a step.
Runners: Sawn-timber beams, used in formwork.
Sarking: Roof boarding or sheeting material and/or
roofing felt.
Scribe; scribing: Techniques used in joinery and secondfixing carpentry for marking and fitting mouldings
against mouldings, or straight timbers against irregular
shapes or surfaces.
Seat cut: The horizontal face of a cut angle.
Set, setting: 1. The alternate side-bending of the tips of
saw teeth. 2. The chemical setting action that brings
initial hardening of glue, concrete, mortar or plaster.
3. A coat of finishing plaster (see Skimming).
Shank: The stem or shaft of a tool or screw.
Shank hole: A small hole made with a twist drill to take
the stem or shank of a screw.
Sheathing: Close-boarding or sheet material such as
plywood or Sterling OSB, fixed to vertical framing
(studs) as a strengthening-skin and a base for cladding
with weather-boarding or tiles.
Sherardized: Ironmongery (hardware), such as nails and
screws, coated with zinc dust in a heated, revolving drum
and achieving a penetrated coating, claimed to be more
durable than galvanizing.
Shuttering: Temporary structures formed on site to
contain fluid concrete until set to the required shape;
shuttering is also known as formwork.
Skew-nailing: Nailing at an angle of about 30–45° to the
nailed surface, through the sides of the timber, instead of
squarely through the edge or face.
Skimming or setting coat: The fine finishing plaster,
traditionally applied to ceilings and walls in a 3–5 mm
thickness and trowelled to a smooth finish.
Soffit: The underside of a lintel, beam, ceiling, staircase
or roof eaves’ projection.
Softwood: A commercial description for the timber used
in industry, which has been converted from needleleaved, usually coniferous evergreen trees, belonging to a
botanical group known as gymnosperms. Occasionally,
the term softwood is contradictory to the actual density
and weight of a particular species. For example, parana
pine is a softwood that is quite heavy and dense, like
most hardwoods.
Spall, spalling: A breaking or flaking away of the face
material of concrete, brick or stone.
Span: 1. Clear span – the horizontal distance measured
between the faces of two opposite supports. 2. Structural
span – for design calculations, is measured between half
the bearing-seating on one side to half the bearing on
the other. 3. Roof span – measured in the direction of the
ceiling joists, from the outer-edge of one wall plate to the
outer-edge of the other.
Spindles: In carpentry and/or joinery terms, this is an
alternative name for balusters and therefore refers to
lathe-turned wooden posts, fixed between the handrail
and string capping or handrail and landing nosing, as
part of the balustrade of a staircase.
Spotting: Marking a trowel-line through a slither of
trowelled mortar when setting out walls and partitions
on concrete foundations or oversites.
Spring or sprung: Warping that can occur in timber after
conversion and seasoning, producing a sprung, cambered
or segmental-shaped edge adjacent to the wide face of
the material. Joists and rafters should be placed with the
sprung edge uppermost.
Stretcher: 1. The temporary timber batten at the base of
a door frame or lining that stretches the legs apart to the
correct dimension until the fixing operation takes place.
2. The long face of a brick.
Appendix: Glossary of Terms
Strut: A timber prop, supporting a load vertically, horizontally or obliquely.
Stub tenon: A shortened tenon, usually morticed into its
opposite member by only a half to two-thirds its
potential size.
Stuck mould or rebate: Moulded shapes or rebates cut
into the face of solid timber members.
Studs, studding, stud partitioning: Vertical timber posts.
Tamp, tamped, tamping: A term used in concreting,
referring to the level surface being zig-zagged and
tamped (compacted) with a levelling board. The tamping
is effected by bumping the board up and down as it is
moved across the surface.
Tang: A square-taper shape at the end of a roundshanked tool.
Tangent: This is a line that lays at right-angles to
another line – known geometrically as a normal – that
radiates from the centre of a circle.
249
Toe: The reference in carpentry to the front of a saw or
plane.
TRADA: Timber Research and Development Association.
Tread: The horizontal face or board of a step.
Twist: 1. Warping that can occur in timber after seasoning and conversion, producing distortion in length to a
spiral-like propeller-shape. 2. Distortion in a framed-up
unit caused by one or more of the members being
twisted, or by ill-formed corner joints.
Voussoir: A tapered brick in a gauged brick arch.
Warp: Distortion of converted timber, caused by changing
moisture content (see Bow, Spring, Twist, Cup and Wind).
Web: The connecting membrane between the flanges of
a steel I beam or channel section.
Wind, winding: These terms are the equivalent of Twist
and Twisting. The expression in wind means twisted and
out of wind means not twisted.
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Index
Abbreviations xv, 6
Adhesive fixings,
flooring panels 85
skirting 214–6
stairs 112–14
Adjustable-strap cramps 102
Aggregate 245
Air bags 182
Alternating-tread stair 122, 129
American projection 3
Angle
(corner) ties 135, 153
fillets 161, 162
Angle-of-lean 45
Angular perspective 5, 6
Apron
flashing 161, 169
lining 105, 119
Arch centres
four-rib 206
multi-rib 208
single-rib 204
twin-rib 205
Arches,
depressed
Gothic 199
semi-elliptical 199
Tudor 200
equilateral Gothic 199
lancet, Gothic 199
segmental 195
semi-circular 194
semi-elliptical 196–9
straight-top Tudor 200–1
Tudor 199, 200
Archformer 193
Arch geometry (methods),
concentric circles 197
five-centred 198
fixed 200
intersecting arcs 196
intersecting lines 196
long-trammel 197
pin-and-string 197
short-trammel 197
three-centred 198
variable 199, 200
Architrave 210, 215
grounds 105
Arris 46, 245
Ashlar studs 168, 170, 245
Auger bits 20
Axes of ellipse 195
Axonometric projections 5
Back gutters 174, 175
Backing
bevel 140
line 139
Backsight (BS) 240
Baffle boards (roof ventilation) 165
Balusters 107, 120–1
Balustrade regulations 122, 123, 130
Balustrades, fixing 118–21
Barge boards 138
Barrier, vapour 86–7, 161–7
Battened floor 86
Battens,
ground 70, 104–6, 115
tile or slate 138
Beads,
clip-in 76
shuffle 75
Beam,
spreader 181
steel 80, 90
Beam compass (trammel) 203
Bearers,
cross 181
stair 118
tank 181
Bedding 157
Bench mark 108
Bevelled housing 89
Bevel formulas (roofing) 148
Bevel, sliding 11
252
Index
Binders 136
Binding (doors) 220
Birdcage awl 23
Birdsmouth,
rafter 140, 245
saw stool 48, 49, 50, 245
Biscuits, wooden 29, 236
Bisecting 194
Bitumen DPM 86
Blind tenon 89
Block plan 7
Blocks,
locating 75, 76
setting 75, 76
Boarding, diagonal 164
Boards,
back-gutter 175
barge 138
fascia 137
floor 84, 85
lay 136
ridge 133–6
saddle 133, 134
soffit 137
valley 137
Boning rods 241
Brace,
diagonal 63, 176, 177
ratchet 20
Bracing 175, 177
Bracing spacer 205
Bracket anchors 78, 79
Brackets, cradling 90, 137
Bradawls 23
Brads,
cut floor 35
Maxi 31
Breather membrane 164, 166
British Standards (BS)
(585: Wood stairs: 1989) 129
(743) 61
(1192: Part 1: 1984) 1
(Part 3: 1987) 1
(1282: 1975) 86
(4978) 81
(5250) 165
(5268: Part 2: 1991) 81
(Part 5) 164
(5395: Part 1: 1977) 124
(Part 2: 1984) 129
Building Regulations, The
Approved Document A 89, 93
(A1/2) 81
(B: Fire safety) 125
(F2) 162, 163
(K, 1998) 122
(L: Conservation of fuel and power) 82
(M: Access and facilities for disabled
people) 124, 125
(Part C) 82, 86
(Part J) 84
Tables A1 and A2 (floor joists) 81, 89
A17 to A22 (roof joists) 160
(N: Glazing – Materials and
Protection) 76
Bullnose step 107, 110, 112
Butts (doors) 221
Cabinet projection 5
Cambered edges 94
Cap,
acorn 121
ball 121
mushroom 121
Capping,
landing 119
string 119
Carcase material 41
Carpenter’s pencil 8
Cartridge
guns (tools) 31
strengths 32
Case clips 42, 43
Cat walk 136
Caulking tool, wooden 75, 76
Cavalier projection 5
Cavity
tray 161
walls 80, 161
Ceiling joists 133
Celotex GA2000 167
Centre bob 10
Centres, arch 203
Chalk line reel 9
Cheeks, dormer 164
Chevron bracing 175
Chimney trimming 174, 175, 180
Chisels,
bevelled-edge 17
bolster 24
cold 24
firmer 17
impact-resistant 17
Chord,
bottom 180
top 175
Cladding 164, 245
Claw hammer 15
Clearance angles (drills) 22
Cleats 51
Clench-nailing 207
Coach bolts 56, 111
Index
Cold deck (flat roof ) 163
Collars,
arch-centre 208
roofing 136
Collimation height 240
Concave shaping (easing) 115
Cone 195
Connectors, timber 58, 89, 175
Convex shaping (easing) 115
Coping saw 14
Corbels 174
Cordless
Angle Finish Nailer 31
circular saw 24
drill 25
jigsaws 27
nail guns 30
planers 27
screwdriver 26
SDS Rotary hammer drills 28
Cornice blocks (architrave) 214
Counter-battens 167
Counterboring 65, 66
Countersink bits 21
Cradling brackets 90, 137
Cramp 246
Cramping method (floors) 84
Cross bearers (tank supports) 181
Crosscut saw 12
Cross-rebates 43
Crowbar 23
Crown 193, 194
rafter 133–5
Crown wool 166
Cupping 43, 246
Curb (skylights) 168
Cut clasp nails 35, 66
Cutting angles (drills) 22
Dado rails 217
Damp-proof
course 83
material 61
membrane 86
Datum 108
Datum level 239
Decking material 161
Deemed length 122, 123
Delaminating (trussed rafters) 176
Diamond
Abrasive Lapping Fluid 19
whetstones 18
Dimensioning sequence 2
Diminish, jack rafter 142, 147
Door
indication 7
Knobs 225
linings 65–7
Doorsets 72
Doors, fire-resisting 73
Dormer windows 164
Double
architraves 213, 214
floors 80
pitch lines (stairs) 128
Dovetailed housing 89
Dovetail joints 42
Dowel,
metal 65, 111
wooden 112
Draw-bore holes/pins 112, 246
Drills,
cordless 26
hammer 22, 26
masonry 22
percussion 26
powered 26
SDS 22, 26
twist 22
Dry lining 192
Easing (strings) 115, 116
Eaves,
closed 136
concealed (in wall) 139, 150–4
diagonal (on hip rafters) 153, 155
drop 153–5
open 136
visible (projecting) 136, 139, 150–62
Edge tools 41
Electronic Detectors 24
Ellipse 195
Escutcheon plates 225
‘E’ staff 240
European projection 3
Expanded metal lath (EML) 69
Expansion gap 83–7
External grounds 106
Extrados 193, 194
Eyebrow window 168
Fall-arrest equipment 182
Fanlight 69
Fan truss 175
Fascia boards 137
Feather-grained 29
Febond adhesive 85
Felt,
built-up (3-layer) 161–3
mineral 161–3
253
254
Index
Fender wall 81, 84
Fillets 42, 43
Finished floor level (ffl) 62, 67, 108
Fink truss 175
Fire-resisting doors 72, 73
Firring 160, 161
First-angle projection 3, 4
Firtree gasket, 76
Fittings (hardware) 42, 225, 226
Five-twelve-thirteen (5:12:13)
method 242
Fixing band 77, 92
Fixings:
cavity fixings 40
Helical warm-roof batten-fixings 167
Inskew 600 fixings
(Helifix) 167
Fixing ties 62, 63
Flange 246
Flashings 161–9, 246
Flat Bits 20
Flight, stair 122
Floor
boarding 84, 85
brads, cut and lost-head 34, 35, 84
clips 86
cramps 84, 85
expansion 84–7
joists 80–103
joist spacings 80
span 81, 87
traps 84, 85
ventilation 81–7
Flooring,
hardwood strip 101
laminate 102
plastic-laminate 102
real-wood laminate 102
Flooring-grade chipboard 84
Floors,
double 80
embedded-fillet 86
floating 85–7
ground 81–7
single 80
surface-battened 86
suspended 81
upper 88
Foresight (FS) 240
Frame
cramps 62
Holdfasts 63
screw-ties, Owlett’s 63
ties 62
Framed grounds 70
Frame-fix screws 39, 40, 64
Frames,
door 60–5
fire-resisting 72, 73
internal 68
storey 69
sub 69
window 74
Framing anchors 89, 138
Free-flighting 31
Gable 132
ladders 179
Gablet 132
Galley kitchen 230
Gang-Nail Systems Ltd 175
Gap-filling adhesives 216
Gas fuel cells 30
Geometrical
shapes 195
stair 123
Geometry,
arch centre 193
roof 140
Girder
trusses 177
truss shoes 179
Glazing safety issues 76
Glue blocks 114, 117, 246
Gluing 113, 114
Going 122–9
Graphical representation 6
symbols 6
Grinding angles (chisels) 17
Gripfill adhesive 216
Grounds,
architrave 105
framed 70
lining 70
skirting 104, 115
wall-panelling 105
external 106
Gusset plate (saddle board) 133, 134
Hacksaw 23
Hammer
drill 25
-fix screws 39, 64
Handboard 54
Handrail regulations 125, 129, 130
Handrails,
fixing 113, 118
protecting 115
Handsaws 12–14
Hangers 136
Hardcore 82, 247
Index
Hardpoint saws 13
Hardwood, definition of 247
Hasp and staple 42
Hatch 136, 180
Hawk 54
Headroom 124, 125
Hearth, concrete 81, 84
Helical stair 123
Herringbone
noggings 186
strutting 92
High-density fibreboard (HDF) 102
High-velocity principle 31
Hinges,
butt 42, 221
piano 42
rising butt 221
strip 42
Hip
flat-top trusses 178
girder trusses 177, 178
mono (or monopitch) trusses 178
rafters 133–5
Honeycombed sleeper walls 81–4
Hop-ups 54, 55
Horns 65
Housing joints 51
Hybrid (flat roofs) 163
Hyperbola 195
Hypotenuse 243
Infill-strip (baluster-spacers) 120–1
Inner
skin (wall) 247
string (stairs) 107–10, 247
In situ concrete 247
Institutional and assembly stair (category
2 regs) 126
Insulating material 82–8, 161–7
Intermediate Sight (IS) 240
Intersection girder trusses 179
Intrados 193, 194
Intumescent
paint 73
paste 73
strip 72, 73
Isometric projection 5
Isosceles roof shape 139
Jabfloor Type (insulation) 70, 85
Jack plane 19
Jambs 65
Jig,
lagging 206
pencil 197
Jigs,
hinge 29, 223
kitchen worktop 29, 236
letter plate 29, 227
lock 29, 228
worktop 29, 236
Joints,
bare-faced tenon 109
bevelled-housing 89
butt 175, 188
blind tenon 89
comb 65
cross-rebate 43
dovetail 42
dovetailed housing 89
framing 88, 89
half-lap 57, 83
housing 89
mortice and tenon 57
oblique tenon 112
single-splay dovetail halving 57
splayed-heading 84
splay-housed, mortice and tenoned 187
square-heading 84
stopped housing 89
stub-tenoned 187
tongued and grooved 77, 84
tongued-housing 67, 117
tusk-tenon 89
Joist hangers 90, 91
Joists,
bridging (common) 88
ceiling 133
sectional-size of 81, 88
table for size of 88
trimmed 88
trimmer 88
trimming 88
return 160, 162, 164
KD
cover caps 238
Fixit blocks 237
Key, arch 194
Kicker strut 113
Knots 247
Knotting 247
Lagging,
close 205
open 205
Lagging jig 206
Laminate:
flooring 102
worktops 235
Landings 123, 125–6
255
256
Index
Latches,
cylinder 226
mortice 225
tubular 225
Lay board 136
‘L’ cleats 101, 102
Letter plate 226
Levelling
instruments 239
staff 240
Levelling-boards, concrete 58
Levels,
boat 9
torpedo 9
Lever furniture 225
Lining leg 61
Linings, door 60
Lintels 193
Load-bearing walls 131, 135
Locating blocks (uPVC windows) 75, 76
Location drawings 7
Locks,
dead 226
mortice 224, 225
rim 226
Louvres 69
Low-velocity principle 31, 32
Mallet 15
Margin 210
template 211
Marking gauges 16
Masonry drills 22
Mastic seal 64
Method Statements 182
Metres 2
Metric rafter square 11, 143
Microllam® 88
Millimetres 2
Mineral wool 73
-wool slab 83
Mitre 210, 211
block 212
box 212
saw 15, 212
square 10
Moisture absorption 70, 114
Moisture vapour 166
Mono (or monopitch) trusses 179
Mortar boards 55, 56
Mounting plates, metal 232, 237
Nail
bar 23
boxes 53, 54
punches 23
Nailers,
Framing 30
Finish 30
Multi T 31
Primatech flooring 102
Spit Pulsa 700P 31
Nailing guns 30
Nails,
annular-ring shank 35
brad-head oval 34, 35
cut clasp 35
grooved-shank 35, 36
lost-head oval 34, 35
lost-head wire 34, 35
masonry 35, 36
round-head wire 34
T headed 34
New Build Policy
Guidance Notes 92, 160, 161
Newel
caps 121
drops (pendants) 121
posts 109–14, 121
Node points175
Noggings,
fixing 186
floor-joist 92, 93
herringbone 186
perimeter 98
roof-joist 159
rafter 159
staggered 186
straight 186
vertical 189
Nosing,
landing 119
tread 123
window board 76
Notching 93, 113
Oblique projections 5
Obtuse angles (on stair-strings) 115
Oilstone boxes 18
Oilstones 18
Open-rise steps 124, 129
Optical squaring instruments 241
Ordnance
Bench Mark (OBM) 239, 240
datum 239
Oriented strand board (OSB) 80, 84, 88
Orthographic projection 3
Other stair (category 3 regs) 126
Outer
skin 247
string 107, 247
Oversite, concrete 83–6
Index
Packing material 67–94
Panel
adhesives 216
bolt connectors 29, 30, 236
pins 36
Panel saw 12
Parabola 195
Parallam® PSL 95, 96
Parallel perspective 6
Partition,
braced (traditional) 183
common (modern) 184–92
trussed (traditional) 183
Pellets 67
Pencil gauge 10
jig 197
Pendants (newels) 121
Percussion drill 25
Perspective projections 5, 6
Pictorial projections 5
Picture rails 217
Pilot holes 23
Pincers 23
Pinch
bar 23
rod 117, 185
Pins, wooden 112
Pitch angle,
roof 131, 139
stair 126
Pitching details (roofs) 156–160, 177–80
Pitch lines,
roof 139
stair 124–8
Plane,
jack 19
power 26
smoothing 19
Planometric projection 5
Planted
moulding 115, 247
stops 65, 247
Plasterboard,
foil-backed 162
sizes of 192
Plasterer’s
board and stand 55
folding stand 56
handboard 54
hop-up 54, 55
Plate connectors 175
Plates,
gusset 134
head 184
sill (floor) 184
wall 83, 156, 157
Plinth blocks (architrave) 214
Plugging 38, 39
Plugs,
colour-coded 38
plastic wall 38
Plumb
bob 10
cut 139
rule 59
Pneumatic nail guns 30
Pocket screwing 114
Polystyrene underlay 85
Polythene sheet vapour-check/DPM 85, 86
Polyvinyl acetate (PVA) adhesive 85
Posi-Joist™ Steel-web system 98
Powered drills 25, 26
Powered planer 26
Powered router 28
Private stair (category 1 regs) 126
Private Stair Regulations 127
Profile
frame 74, 248
lining 72, 248
pattern pair 176
Profiles 241
Props, timber 116, 209
Protection strips 61, 115
Protractor facility,
metric rafter-square 143–6
Roofmaster square 147, 148
Pullsaws 14
Punch, nail 23
Purlins 136, 158
Quarter-turn stair 116
Quilt,
mineral wool 73
Radius rod 203
Rafters,
common 134, 150
cripple 142, 146
crown 134
hip 133–5
jack 142–146
pattern 150, 151
pin (crown) 134
trussed 175
valley 138, 157
Ranging lines 241
Ratchet brace 20
Reduced Level (RL) 240
Reflex angles (stair strings) 115
Resin-bonded 248
Restraint straps 133, 159, 160
Reveals 248
257
258
Index
Rib formation,
semi-hexagon 208
semi-octagon 208
Ribs 203–8
Ricochets 31
Ridge board 133–6
Rip saw 13
Rise,
arch geometry 193, 194
roof 139
stair 123, 124, 126, 127
Riser board 107, 114
Risk Assessments 182
Roof
design 132
falls 137, 161
hatch (trap) 136, 180
windows 164, 168
Roof,
flat 131, 160–2
gable 132
gambrel 132
hipped 132
jerkin-head 132
lean-to 131
mansard 132
pitched 131
trussed-rafter 175–81
valley 132
Roofing
bevels 139–57
felt, built-up 161–3
formulas (bevels) 148
Ready-Reckoner 141
square 11, 143
Roofing,
modern 175–82
traditional 131–74
Roofmaster square 11, 147
Rose plates 224
Rounded step 129
Rule,
folding 9
scale 2
steel tape 8
Run,
common rafter 139–50
hip 140–50
scaled 145
Runners 41, 248
Saddle and block (door-hanging device) 219
Saddle board 133, 134
Safety
glass 76
nets 182
Safety bracing (floor joists) 98
Sarking 248
Saw
pitch-angle 13
stool 45
Saws,
electric circular 24
hand 12
Scale rules 2
Scales 2
Screw gauges 36, 221
Screwdriver bits 22
Screwdrivers 16
Screwing and pelleting 66
Screwing, pocket 114
Screws,
Allen recessed head 37
bugle-shaped head 34, 36
collated floorboard- 34
countersunk head (CSK) 36
Frame-fix 39
Frame 39, 40
gauge of 36
Hammer-fix 39
nylon-sleeved 39
Phillips’ head 37
Pozidriv head 37
raised head (RSD) 36
round head (RND) 36
single-thread 37
spaced-thread 37
square recessed head 37
Supadriv head 37
Torx or T Star-slotted 34, 37
twinfast-thread 37
Window-fix 39
Scribing 213, 215
technique 213, 215, 216
SDS
chuck systems 21
drills 22
-Max chuck 28
-Plus chuck 28
Seat cut 139
Setting blocks 75, 76
Setting out
arch shapes 193–202
boards 207, 208
common rafters 150
crown rafters 151
hipped ends 159
hip rafters 152
jack rafters 155
partitions 183, 184
Setting-out pegs 240
tapered treads 123–30
Index
terms (roofing) 138, 139
(stairs) 107
wall plates and ridge board 157
Shank holes 114
Sharpening
angle 18
oil 18
procedure 18, 19
Sheathing 164, 170
Shims, plastic 75
Shrinkage 71, 115
Silent Floor® System 88
Sill 62, 64, 183
Silicone sealant 75
Single
floors 80
pitch-line 124, 128
Site plans 7
Skew-nailing 114, 185
Skin,
inner (wall) 247
outer (wall) 247
plywood or hardboard 205
Skirting 215–17
bullnose 217
chamfered 217
dual pattern 217
Grecian ogee 217
grounds 104, 115
ovolo 217
torus 217
Skylights 168
Sleeper walls 81–3
Smoothing plane 19
Soffit 60, 248
boards 137
Softwood, definition of 248
Soldier pieces 105
Spacing (infill) strip 119–21
Spalling 32
Span 139, 193
Spandrel 107
Spindle (lock) 224–6
Spindles (stair) 107
Spiral stair 124
Spirit level 9
Splayed step 116, 129
Splicing 213, 216
Spot boards (see mortar boards)
Spotting 68
Spreader beam 181
Springing line 193
Sprocket pieces 137
Sprung edges 158, 248
Square,
builder’s 56, 57
combination mitre 10
roofing 11, 143
Roofmaster 11, 147
Squaring technique 243
Stability/integrity rating 72
Stair
formula 126, 127
gauge fittings 144, 145
width 125
Staircase 107
Stairway (see flight)
Stairwell 88
Stakes 241
Steel square 11
Stepped measurements 244
Stepped soldiers 105
Steps,
parallel 116
tapered (winding) 116, 124
Storey frames 69
height 109
Straightedges 9, 58
Straining pieces 136
Stretchers 66, 67
Striking plate 225, 228
String-line technique 104
Strings,
inner 107–10, 247
outer 107, 247
return 117
wall (see inner strings)
Strongbacks (in Posi-web floors) 101
Structurally-graded timber 81
Struts 113, 136
Strutting 91
Stuck
moulding 115, 249
rebate 65, 249
Stud,
corner 189
door 185
door-head 185
intermediate 185
wall 184
Studding
fixing problems 191
junctions 189
spacings 192
Sub frames 69
Sunken rebate 65, 248
Surveying/measuring tapes 241
Suspension brackets 232, 237
Swollen timber 70, 114
Tangential cuts 204
Tank supports 181
259
260
Index
Tapered treads 116, 122–4, 128
T-Bars 102
Templates,
arch centre 207
margin 211
saw stool 47, 48
Temporary Bench Mark (TBM) 240
Tenon saws 13
Third-angle projection 4, 5
Three–four–five (3–4–5)
method 57, 157, 242
Threshold 64, 71
Through-dovetails 42
Tie beams 206
Ties,
angle (corner) 135, 153
fixing 62, 63
roof (see ceiling joists)
Tilting fillets 137, 138
Timber connectors 89
Timberstrand™ LSL 95, 96
TJ-Beam® software 96
TJI® joists 95
TJ-Xpert® software 96
Toothed timber-connectors 58, 191
Trammel
beam compass 203
frame 204
rod 203, 204
Transom 69
Trap, roof 136, 180
Tread 107, 123
Trim-It™ floors 99
Trusses,
Fan 175
Fink 175
flat-top 178
girder 177, 178
hip girder 178
hip mono 178
mono or monopitch 179
W 175
Trus Joist 87, 88
Turn buttons 44
Turning piece 203
Tusk tenon joint 89
Twist 249
bits 20
drills 22
Tyvec®
Butyl Tape 167
Eaves carriers 166
Solid membrane 167
Supro membrane 164
Supro Plus membrane 167
Uni-Screw heads 34, 37
Upper floors 88
uPVC windows 74
Valley
boards 137, 138
frames, diminishing 179
junctions 179
rafters 138, 157
Vapour check (barrier) 85–7, 161–6
Vee-ended stool 53
Ventilation,
floor 81–8
roof 137, 163–6
Verge 135, 138
projection 138
Viability Graph 127
Vials 9
Voussoirs 193, 194
W truss 175
Wall
bearings 80, 91
plates 83, 156, 157
strings 107–10, 247
studs 184
Warm deck (flat roof ) 163
Warp 249
Water bars 64
Waterproof adhesive tape 85
Weatherboard 64
Web 249
Wedge gasket 75
Wedges 209
Wet trades 60
Winder,
half kite 116, 117
kite 116
skew 116, 117
square 116, 117
Winding 249
sticks 52
Window
boards 76
indication 6
Windows,
casement 74
dormer 164
eyebrow 168
fixing 74
roof 168
skylight 168
uPVC 74
Work triangle, the 230
Wrecking bar 23
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