guide to External Fire Retardant

guide to External Fire Retardant
External timber
Fire Retardant
Timber preservation, fire retardants and coatings
Treated Timber Specification
Sentrin FRX fire retardant treated timber has been pressure impregnated with a leach resistant (Type LR), exterior grade fire
retardant formulation. It has been processed under ISO9001 controlled factory conditions to provide confidence in
performance and long lasting protection without further maintenance, even in fully weather exposed situations. Treated
timber can meet the requirements of national Building Regulations where Euroclass B or C are required and will significantly
reduce the spread of fire, heat generation and smoke generation. These fire performance properties do not compromise
critical engineering properties such as strength, durability, corrosivity and hygroscopicity.
How do I specify the correct treatment?
Sentrin FRX treated wood products have been tested to BS
EN 13501-1:2002; Fire classification of construction products
Flammability Classifications
Transposition to BS476
and building elements. These ‘reaction to fire tests’ are used to
generate classifications of flammability which are commonly
specified in building regulations. To specify the correct level of
protection the following information is required:
1. Timber species or plywood type and dimensions.
2. Euroclass required (C or B).
3. End use application.
Very limited combustibility
Class O
Class 1
Class 3
What is the Service Life of the treated wood?
Contact us for assistance with detailed specification writing.
Sentrin FRX treated wood products are designed to perform
Sentrin FRX treated wood products meet the requirements of
for the life of the building or structure and require no
LR (leach resistant), HR (humidity resistant) and DI (dry
maintenance. Treated timber has maintained its fire
internal) specifications.
performance in the ASTM D2898 accelerated weathering
What is the appearance of the treated timber?
test, used to approve leach resistant, exterior grade fire
retardant treatments.
Treatment with fire retardant in general, does not alter the
appearance of the timber or wood based panel. Some slight
Typical applications
darkening may occur which will be dependent on the timber
For use in above ground and exterior applications such as
species and the kiln drying process following treatment. There
cladding, decking, shingles, exposed structural timber and
may also be some surface deposits which will not affect the fire
playground equipment.
Timber can be exposed to weathering without
The treatment process involves pressure impregnation with a
compromising the fire performance. If a coating is required
warm liquid followed by at least 72 hours in a high temperature
for aesthetic reasons, Sentrin Chromacoat can be factory
kiln. Consideration should be given as to whether the material
applied. Other coating systems may not be suitable and must
to be treated can withstand this process and we can provide
be tested prior to application.
It is always recommended that representative samples are
processed prior to full scale treatment, especially if a coating is
to be subsequently applied.
User Guide
Storage of treated timber
Following treatment, kiln drying and high temperature curing will reduce the moisture content to below 28%. Treated timber is
usually wrapped following drying to protect from weathering and dirt. If extended storage is required before installation, the
wrapping should be removed to promote airflow through the timber.
Re-working of treated timber
Treated timber should not be machined, planned or milled following treatment. Light sanding with a fine grade sandpaper is
acceptable and will not affect the fire retardant properties. Timber may be cross cut without the need for re-treatment if the cut
ends are butting together in the final structure. Refer to health & safety guidance if any re-working is to be carried out.
Treated and dried wood poses similar hazards as untreated wood. Engineering controls and protective equipment should be used to
minimise airborne wood dust.
Metal fixtures and fastenings
Certain metal products may corrode when in direct contact with wood exposed to water.
Stainless steel or hot dipped galvanised metal fittings are recommended.
Painting and staining
Sentrin FRX treated wood contains resins which are used to improve leach resistance during
weathering. Many paint systems are incompatible with the treated wood and poor adhesion
may occur. PTG Treatments offers factory applied compatible coatings systems in Sentrin
Chromacoat, which has been specifically developed for this application Samples should
always be tested to ensure that the coating provides the intended result.
Treatment Process
Treatment is carried out in high pressure autoclaves to penetrate fire retardant into
the timber to achive the required classification. Timber is loaded into the treatment
vessel and the door sealed. A vacuum is then created inside the to remove air from
the timber. The vessel is flooded with fire retardant solution and high pressure
applied to penetrate into the timber. After the solution is removed a final vacuum
is created to remove excess liquid. The liquid is returned to storage and there is
no waste generated from the process. The freshly treated timber is then held
undercover until it is drip dry before being kiln dried and then heat cured..
Process times vary with the treatment specification but are typically between 90
and 240 minutes. Drying and curing can take up to 2 weeks.
User Guide
Confirmation of treatment
Every consignment of treated timber is issued with a treatment certificate which confirms the fire retardant classification. This is
an important document and may be required by a building regulator. Classification reports are available to be used in conjunction
with the treatment certificate. If required, individual items can be stamped with the fire classification to aid identification.
Quality Assurance
Treatment is carried out under controlled factory conditions and the process is ISO 9001 accredited. A computer controlled
treatment process ensures the correct retention of fire retardant to achieve the required classification. Sentrin FRX is an
impregnated fire retardant and cannot be applied by hand, brush or spray. It provides a level of confidence in performance that
may not be available with treatments applied on site or in uncontrolled conditions.
How it works
When subjected to a fire, the protection technology reacts with the combustible gases and tars normally generated by untreated
wood, converting them to carbon dioxide and water. The layer of char formed on the surface insulates and retards the process
of combustion reducing ignition, the rate of spread of flame, smoke propagation and the amount of heat released. This should
provide increased time for escaping from a building or structure.
Construction Products Regulations and CE marking
UK Building Regulations
Under the EU Construction Products Regulation (CPR),
The fire performance for all material that are to be used in
from 1 July 2013 a construction product will need to be CE
buildings, including wood and wood based panels are stated
marked and accompanied by a declaration of performance
in Document B of the UK Building Regulations:
if it is to be placed on the market in the European
Wall and ceiling linings are Class 1 Surface Spread of Flame
Economic Area and it is covered by either a harmonised
in accordance with BS476:Part 7 or Euroclass C in
European Product Standard or a European Technical
accordance with BS EN13501-1:2002.
Assessment. It is the responsibility of the company or
Higher risk areas, such as escape routes and staircases, and
person placing the product on the market for the first time
external cladding are Class 0 (BS476:Parts 6&7) or
to ensure the CE mark is correct and accurate. PTG
Euroclass B (BS EN13501-1:2002).
Treatments can supply the information required to
These standards relate to ‘reaction to fire’ of a material and
complete a Declaration of Performance (DOP).
not ‘fire resistance’ as in 30 or 60 minute specifications.
Health Safety and Environmental
Sentrin FRX fire retardant treated timber has been pressure treated with a waterbased leach resistant (Type LR) fire retardant.
Many of the health & safety recommendations are the same as those for working with untreated wood.
Health & Safety
● Wear a dust mask, eye protection and gloves when working with wood.
● Treated wood should not be used where it may come into direct or indirect contact with drinking water.
● Do not use treated wood where the preservative may become a component of food, animal feed or beehives.
● Do not use treated wood for mulch.
● Wash exposed areas of skin following handling or working with treated timber.
● Launder heavily soiled clothes separately after working with treated timber.
Waste Disposal
Industrial Emissions Directive
Further information
Sentrin FRX treated timber is not
Wood treatment facilities are
For further information on any
considered as hazardous waste.
covered by EU Industrial Emissions
aspect of timber protection,
Dispose of treated wood and
Directive (IED) which promotes
contact PTG Treatments. Our
waste according to local authority
best environmental techniques to
literature is constantly updated to
regulation. Treated wood will not
reduce and control the impact of
reflect regulatory changes. This
readily burn but can be disposed of
industrial emissions. All PTG
document is uncontrolled so please
in commercial incinerators or
treatment centres comply with the
make sure you have the latest
landfill to local regulations.
requirements of the IED.
version which can be downloaded
Timber Preservation, fire retardants and decorative & protective coatings
Contact Us
Telephone 01777 709855
Treatment Centres Tilbury
01375 858700
01482 329114
01236 720992
01738 635521
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