Photos courtesy of ProWood

Installing FRTW in buildings can take many forms in walls, floors, roofs, and even interior blocking and backing.

FRTW is not permitted for applications where the material may be exposed to precipitation, direct wetting, or regular condensation, and should never be used in contact with the ground. Ventilation should be provided in compliance with the applicable codes in force at the time of construction. If the wood is to be used in an interior application and becomes wet during construction, it should be allowed to dry before being covered or enclosed.

Typical joining cuts, end cuts, and drilled holes will not adversely affect the fire performance of FRTW, and no field treatment is required to maintain flame spread ratings. However, ripping or milling of FRT lumber is not permitted, as these operations could adversely affect the surface burning characteristics, however, end cuts are permitted. FRT plywood can be ripped as required. FRTW plywood can be cut along either dimension.

Fasteners: The fasteners used in FRTW must be selected to avoid corrosion or degradation from either the treatment chemicals or the installation conditions. Therefore, galvanized steel, stainless steel, silicon bronze or copper, in accordance with applicable sections of the IBC must be used. Even though the FR treatment may not increase corrosion of bare or galvanized steel, galvanizing provides an added level of protection with any treated wood product. The fasteners may also be subject to design value adjustments when specific products are evaluated using an ICC Evaluation Service (ICC-ES) report.

• Jobsite Safety: Some of the safety recommendations of manufacturers of FRTW include the following.
• Do not burn fire-retardant-treated wood.
• Wear NIOSH N95 dust mask and goggles when cutting or sanding wood.
• Wear gloves when working with wood. Some fire-retardant-treated wood chemicals may migrate from the treated wood into soil/water or may dislodge from the treated wood surface upon contact with skin - Wash exposed skin areas thoroughly.
• Wash work clothes separately from other household clothing before reuse.
• Fire-retardant-treated wood should not be used where it may come into direct or indirect contact with drinking water.
• Do not use fire-retardant-treated wood where it may become a component of food, animal feed, or beehives.
• Do not use fire-retardant-treated wood as mulch.

• Waste Disposal: All sawdust and construction debris should be cleaned up and disposed of after construction. Fire-retardant-treated wood may be disposed of in landfills or burned in commercial or industrial incinerators or boilers in accordance with federal, state, and local regulations.
• Finishing: FRTW that is visible in construction or otherwise in need of a finish can be covered using most conventional wood finishing methods. Under normal temperature and humidity conditions, latex, and oil-based paints, as well as water- and solvent-based stains, can be used with FRTW. If prolonged exposure to high humidity conditions is expected, special surface preparation procedures including the use of an appropriate primer are recommended. Before applying any finish, the wood surface should be lightly sanded, cleaned and dry. For the best results, always follow the coating manufacturer’s label instructions.
• Maintenance: Mold growth can and does occur on the surface of many products, including untreated and fire-retardant-treated wood, during prolonged surface exposure to excessive moisture. To remove mold from the treated wood surface, wood should be allowed to dry. Typically, mild soap and water can be used to remove the remaining surface mold.

CONCLUSION

Buildings of all types need to address fire safety. While different combinations of materials and structural systems are possible under the codes and widely used, FRTW is seen as a proven and often preferred material to achieve a readily constructible and fire-tested solution. The end result is that incorporating FRTW into wall and roof assemblies can help make the difference in providing greater safety and lowering the number of casualties due to fire in all types of buildings.

Peter J. Arsenault, FAIA, NCARB, LEED AP is a nationally known architect and a prolific author advancing safer buildings by design. www.pjaarch.com, www.linkedin.com/in/pjaarch