Tests of Fire-Retardant Treated and Untreated Lumber-Plywood Nailed and Stapled Joints

Eight different fasteners–either nails or staples– were used to fabricate joints that were exposed for 0, 2, and 7 years in standard (70?F and 65 percent RH) and cold (35?F and 70 percent to 80 percent RH) rooms. Joints were between Douglas-fir dimension lumber and 3/8-inch plywood, with either one or both treated with NON-COM, Pyresote, or borax-boric acid fire-retardant, or left un treated. Loads were recorded for lateral bearing tests at deformations of 0.015, 0.02, 0.03, 0.04, 0.05, and 0.10 inch. Data for joints exposed for 0 and 7 years are tabulated. Load-deformation results were little different among joints exposed for 0, 2, and 7 years in standard or cold conditions. Exposure to cold conditions up to at least 7 years slightly increased the lateral-bearing strength of lumber-plywood joints compared to joints exposed to standard conditions. Results were little different whether the lumber, plywood, or both were treated or not. The 6d common nail was the strongest fastener at lower deformations; the 6d common, the 6d hot-dip galvanized, and the 6d monel nail were about equal, and strongest for overall performance in joints tested to failure.

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