INTERNATIONAL BUILDING CODE              

Uses Noncombustible Type Construction - Untreated wood is not permitted. Fire-retardant-treated (FRT) wood may be used in specific instances.

Criteria Fire-retardant-treated wood is any wood product pressure-impregnated with chemicals or other means during manufacture having a flame spread classification of 25 or less and showing no evidence of significant progressive combustion when the test is continued for an additional period of 20 minutes total of 30 minutes. In addition, the flame front shall not progress more than 10.5 feet beyond the center line of the burners at any time when tested in accordance with ASTM E 84. {Ref.: IBC Section 2303.2}

All fire-retardant-treated lumber and wood structural panel products shall be properly labeled with the identi fying mark of an approved testing agency, identification of the treating manufacturer, name of fire-retardant treatment, wood species treated, flame spread and smoke developed index, drying method used after treatment and conformance with appropriate standards as required by Section 2303.2.2 through 2303.2.5.. For fire-retardant-treated wood exposed to weather, damp or wet locations, include the words “No increase in the listed classification when subjected to the Standard Rain Test” (ASTM D 2898). {Ref.: IBC Section 2303.2.1}

Design values for untreated lumber and wood structural panels shall be adjusted for strength for fire-retardanttreated wood. Design value adjustments shall be based on an approved investigation method that considers the effect of the anticipated temperature and humidity that the fire-retardant wood will be exposed to and the type of treatment and re-drying procedures used. {Ref.: IBC Section 2303.2.2}

Fire-retardant-treated wood structural panels (softwood plywood) shall meet the requirements of ASTM D 5516 and ASTM D 6305 where applicable. Each manufacturer shall publish the allowable maximum loads and spans for floor and roof sheathing for its treatment. {Ref. IBC Section 2303.2.2.1}

Fire-retardant-treated lumber shall meet the requirements of ASTM D 5664 for each species of wood treated. Each manufacturer shall publish the modification factors for service at temperature of not less than 80° F and for roof framing. The roof framing modification factors shall take in consideration the climatological location. {Ref. IBC Section 2303.2.2.2}

Where fire-retardant-treated wood is exposed to the weather, damp or wet locations it shall be identified as “Exterior” to indicate there is no increase in the listed flame spread index as defined in Section 2303.2 when subjected to ASTM D 2898.  Where fire-retardant-treat ed wood is exposed to exterior conditions, it shall be identified as “No increase in the listed classification when subjected to Standard Rain Test” indicating the listed flame spread classification has not increased when subjected to ASTM D 2898. {Ref.: IBC Section 2303.2.3}

Interior applications of fire-retardant treated wood shall be marked “Type A” and not have a moisture content greater than 28 percent when tested using ASTM D 3201 procedures at 92 percent relative humidity. {Ref.: IBC Section 2303.2.4}

Prior to use fire-retardant-treated wood shall be dried to a moisture content of 19 percent or less for lumber and 15 percent or less for wood structural panels. Wood kiln dried after treatment (KDAT) shall not exceed the kiln or drying temperatures used previously to dry the lumber and plywood. {Ref.: IBC Section 2303.2.5}

Buildings of Type I and II construction have limited applications for fire-retardant-treated wood as required by IBC Section 603.1. {Ref.: IBC Section 2303.2.6}

Hardwood and decorative fire-retardant-treated wood plywood shall be manufactured and identified as required by Hardwood Plywood Veneer Association Standard HPVA HP-1. {Ref.: IBC Section 2303.3}

Fasteners for fire-retardant-treated wood shall be of hot-dipped zinc-coated galvanized steel, stainless steel, silicon bronze or copper. Fastenings for wood foundations shall be as required in AF&PA Technical Report No. 7. {Ref.: IBC Section 2304.9.5}