Status of Com-Ply Floor Joist Research

COM-PLY, is a structural sandwich product with a core of particleboard between layers of parallel-laminated veneer. Forest resource studies show that trees provide a sufficient volume and grade of veneer to permit total tree conversion into COM-PLY wall or floor framing. Structural tests show COM-PLY joists have a stiffness about 80 percent that of solid lumber of the same species. The strength of COM-PLY joists exceeds performance levels. Durability and dimensional stability in weathering and laboratory accelerated aging of joists are discussed. In similar studies, COM-PLY studs lost 9 percent of their strength and 9 percent of their stiffness after 24 months of outdoor weathering. COM-PLY studs are more dimensionally stable than sawed solid-wood studs and are essentially warp-free even after long exposures to outdoor weathering. Fastener strengths and rigidities for typical methods of supporting joists meet the strength and deformation limits expected in floor construction. COM-PLY studs have less fire resistance than solid lumber. Sound transmission through walls framed with COM-PLY lumber is about the same as for walls framed with solid lumber. COM-PLY joists can be manufactured for about $160 per thousand board feet at 1978 price levels and can therefore compete very favorably with conventional solid-wood joists in the marketplace.

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