Fire rated is not a buzzword as fire retardant treatments are meant to reduce the rate at which wood will catch fire and how quickly flames can spread while only seconds matter to escape or fight a conflagration.
What is the difference between fire retardant treated and fire resistant?
Timber is naturally combustible. Fire retardants function by modifying how wood responds to heat. According to the product they can:
Reduce surface flame spread
Reduce heat release
Embrace charring, not fast burning
Allow material to naturally self-extinguish when source of ignition is taken away (in some circumstances).
One must differentiate between reaction to fire (how well the material resists flame) and fire resistance of a wall, floor or door being able to contain that much time for their specific function. A“fire-rated” wall is a system as tested, not just one board. For advice from Timber Merchants Portsmouth, contact www.timbco.co.uk/timber-merchants-portsmouth/
Process of fire treatment
You’ll usually see two approaches:
Factory High Pressure Impregnation: Chemicals are pressed into the timber under high pressure. This produces a deeper penetration and much more consistent performance.
Surface-applied coatings/paints: applied after manufacture. They perform quite well, but the degree of coverage and depth is very crucial to how it behaves over time.
Fire performance may be intrinsic to the product (through its structure), or can also come from a treatment or fire retardant coating. Be sure to always refer to the product specification instead of generalising all types of wood.
The real world meaning of “fire retardant treated”
As a properly specified fire-retardant product, documentation should include:
Fire classification obtained (typically based in European/UK testing standards)
The application of the rating is simply for internal use, or also it can be used publicly as well.
Depending on the type of treatment, some are leachable. For this reason, a product that works well in dry internal conditions is not necessarily going to be appropriate for outdoor cladding unless it has an external-rating.
Common mistakes to avoid
No such thing as “fireproof” (unless treated)
Using internal-rated treated timber outside
Leaving boards unsealed/ and other exposed cut ends
Not verifying full system requirements before mixing products
The takeaway
It is essential to remember that fire retardant timber and sheet materials are not riskfree, they only slow the growth. Agree to those that have a clear test certification as required for compliance in building projects and ensure the rating is well-matched with where it will be used such as internal or external locations.