Plywood is similar to solid wood with comparable
density and thickness and in its behaviour towards fires. Fire retardant
characteristics of plywood are integral in preventing the propagation of fire
at the initial stage. For certain use cases, such as in marine constructions
and railway coach construction, the use of fire treated plywood is desirable.
Chemicals that enhance fire resistant properties of
the wood are introduced at the veneer stage itself. However, in some
impregnation methods, fire resistant properties are introduced in the plywood
after its manufacturing. Some fire retardant chemicals may require special
paints. FRT plywood is widely used as roof sheathing in multifamily dwellings as
party-separation walls. The use of FRT plywood as a substitute for parapet
walls has also increased.
Types of retardant formulations
Most plywood is treated with Type A or Type B
interior-type fire retardant formulations. These two treatments are categorized
by their hygroscopicity which is a measure of the tendency of the material to
absorb moisture from the air, as measured by ASTM (American Society for Testing
and Materials). Type A fire rated (FRT) plywood is intended for use in
environments where the relative humidity is less than 95 percent when the wood
is not exposed to elements. Type B FRT plywood is intended for use in areas where
relative humidity generally does not exceed 75 percent.
FRT wood and building codes
Fire retardant chemicals are used in wood products for
the construction of interior panelling, scaffolding and military buildings. The
treatment for wood shakes and shingles is a more recent application. Certain
building codes allow for the use of FRT lumbar as an alternative to non-combustible
materials for walls and partitions. Some codes also allow for the use of FRT
wood for roof sheathing and roof structural framing in certain types of
building constructions. All codes allow FRT plywood in roofs of buildings where
wood construction is permitted. A combination of chemicals that buffer the
treating solution and encapsulate the fire retardant chemical can alter the pH
and acidic strength of the treating solution while retaining the effectiveness
of the fire retardant chemical.
Standards for comparing FRT
ratings
All FRT rated plywood and boards should bear an
identification mark indicating the flame spread identification. To be
classified as a fire rated board or fire rated plywood, the wood product should
have a flame spread index of 25 or less when impregnated with chemicals by a
pressure process. The flame spread and smoke index for non-combustible ceramic fibreboard
is 0. It is 100 for solid red oak panels. These two indexes are used for
comparing FRT ratings of other wood products.
Exterior fire retardant treatment is undergone for
fire rated board after it is subjected to an accelerated weathering test.
Exterior FRT plywood is used in environments where a relative humidity of 95
percent or more is expected or where high resistance to the leaching effects of
moisture is desired.
Adding to the look and longevity
Plywood increases the aesthetic and longevity of your
furniture, structural elements and other woodwork projects. Ventilation is
essential in all constructions to minimize excess relative humidity and to
prevent moisture build up. Good ventilation helps control the moisture content
of roof systems as moisture cannot be flushed out of a roof plenum in the
absence of proper air movement.
Fire rated plywood offers resistance to ignition,
surface spread of flames and flame penetration. Low flammability of fire rated
board significantly reduces the damage due to fire in your office and home.
Fire resistant boards and fire resistant plywood are specially treated to
generate low amount of smoke in the event of a fire, thus cutting down the
emission of toxic gases like carbon dioxide.
Best quality FRT wood for
commercial and residential uses
Fire rated board and fire rated plywood from reputed
brands such as Matilda Veneer are designed to delay the spread of fire on the
material by 30 minutes. They stay composed in structure even if the board or
plywood is entirely burnt down. It will take 45 minutes or more for the flames
to penetrate through the fire rated plywood and fire rated board so the
building occupants will have enough time to run for safety before the plywood
walls disintegrate. FRT wood by Matilda Veneer is lightweight and economical and
can be easily cut and sized on site, and also nailed, refinished and easily
transported. These can be used as a substitute for a parapet wall between
attached multi-family units, and institutional buildings such as nursing homes
and schools, where entire roof assemblies may be constructed using high-quality
fire retardant plywood and fire retardant board by Matilda Veneer.