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Fire-retardant chemicals reduce the design properties of the wood. In addition, for engineered wood products, the treatments may not be compatible with the adhesives used. The designer is cautioned to verify the effects of fire-retardant treatments (with the supplier) on the strength and performance of any wood product prior to specifying.

Fire-retardant paints and stains can effectively reduce flame spread when properly applied. While typically applied to large expanses of interior wood surfaces such as panel products, they can be applied to timber members when a specific flame-spread rating is required per design regulation. However, it is important to understand these coatings do not increase the fire-resistance rating for large timber or glulam members.

SPRINKLER SYSTEMS
Automatic sprinkler systems have an excellent record of improving fire safety and reducing losses. Many fire codes require that automatic sprinkler systems be installed in commercial buildings, and in some cases, added to existing buildings.

Such sprinkler systems may improve the fire-resistance and flame-spread ratings for a building’s struct-ural system. As a result, an additional storey of height or an increased building area may be permitted (by the codes) for buildings with sprinklers. Sprinkler systems also reduce insurance premiums—with the result that a sprinkler system often pays for itself within a matter of years, depending on the value of the building and its contents.

In addition, the more expensive construction methods required for noncombustible materials increase the cost of financing a project. Increased financing costs generally exceed any potential savings on insurance. Thus, using more expensive construction methods, in order to gain lower insurance rates, may actually result in increased overall costs.

INCREASING ALLOWABLE AREAS FOR HEAVY TIMBER CONSTRUCTION
U.S. building codes place height and area limitations on buildings to safeguard building occupants. While wood construction is typically assigned the lowest, basic allowable heights and areas, the model building codes also provide many options for increasing allowable areas. The following list provides suggestions for how to increase, under U.S. model building codes, the allowable areas for wood construction while maintaining life safety for building occupants:

1. Provide one-hour fire-resistive ratings for structural members and assemblies.
2. Install automatic sprinkler systems.
3. Maintain separation between buildings where possible.
4. Seek unlimited areas where appropriate, for specific types of building uses, by providing open spaces around the building combined with the use of automatic sprinklers.
5. Install properly constructed area-separation walls with protected openings.