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In a wide variety of residential and commercial applications, the use of fire retardant treated (FRT) wood can reduce the effects of fire and improve the safety of buildings and construction sites. FRT wood is economical, recognized by most major building codes and available in many common lumber and plywood sizes for easy use on the job.

Arch Wood Protection first introduced fire-retardant wood in 1981, under the trade name of Dricon FRT. When exposed to a fire, the chemicals react with the combustible gasses normally produced by untreated wood as it burns, converting them to carbon char, carbon dioxide and water. This protection greatly reduces the damage caused by the fire, since the char slows the rate at which the cross-sectional area of the wood is reduced, so the wood does not lose its strength characteristics as dramatically as untreated wood. Also, the carbon dioxide and water vapor produced help reduce the spread of the flames.

FRT wood is a good choice for use where untreated lumber or plywood products might permit a fire to spread rapidly. This includes cabins and other remote structures where water supplies or fire protection are inadequate, residential and commercial applications where the installation of sprinklers is difficult, such as under raised floor areas, under theater stages or other raised platforms, or in many remodeling situations, and in just about any floor, wall or roof framing application. It is also excellent for use in temporary facilities such as scaffolding, staging, job shacks and other job-site structures that are not normally protected against fire.

For exterior applications where the wood or plywood will be directly exposed to weather, there is FRX. FRX exterior wood is also available in common lumber and plywood sizes, as well as shakes and shingles for roofing and sidewall applications. The borate ingredient in the fire-protection solution makes the wood a less than ideal food source, so it is resistant to termite and fungal damage as well. FRX should not be confused with conventional pressure-treated lumber, however, and is not intended for below-grade or ground-contact applications.


There are certain cutting and handling procedures that need to be followed with FRT and FRX lumber. Cutting the boards to length and drilling holes in them is permissible, and the cut ends do not need to be treated. However, to avoid compromising the chemical protection the lumber should not be ripped or milled, although ripping plywood is acceptable.

Handling treated wood is similar to handling untreated wood, and you should follow the same types of common sense precautions. Use of a dust mask and safety goggles are recommended for protection against airborne dust and wood chips, as well as the use of gloves for protection against splinters and washing your hands after work.

Both FRT and FRX wood can be finished with paint or stain, although the chemical treatments used in FRX may limit some of the finishes that are compatible with it. Fire treatment may also cause some reduction in the strength characteristics of the wood, depending on the species. Prior to designing any structure or applying any surface coatings, talk to your lumber dealer about obtaining a strength adjustment chart, as well as the latest listing of coatings that have been tested and verified as acceptable.

FRT lumber is available in a variety of wood species, including several types of pine and fir as well as hemlock, poplar, redwood, oak, cedar and spruce. In plywood form, it is available in fir, pine and redwood. FRX is available in Douglas fir, southern yellow pine, hem-fir and western red cedar. All are available by special order from most lumber yards and they can also provide you with additional product specifications and application information.


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