Evaluation of reduced-thickness studs

Reduced-thickness studs, measuring just 1-1/4 inches thick, are being manufactured and marketed by a northern Idaho sawmill company. The studs meet Western Wood Products Association grade standards for stress-rated boards, which allows the assignment of allowable design values. Our evaluation of these reduced-thickness studs included a Best-Opening-Face (BOF) computer estimation of the increased lumber yield, preliminary determination of allowable bearing loads, and a field evaluation in which the studs were used in the construction of a single-family home. The BOF estimation for lumber yield from 9-inch mean diameter, 8-foot logs indicated possible 18 percent increase in recovery when 2 by 4 studs are the primary product being manufactured. In addition, when 2 by 4 and 2 by 6 studs were the primary products being produced, 24 percent more 2 by 4 studs and 14 percent more 2 by 6 studs could be manufactured by sawing to reduced thickness. Engineering calculations demonstrated that the reduced-thickness studs, graded as No. 2 Stress-rated Boards, will support approximately 80 percent of the load-bearing capacity of full-sized 2 by 4 and 2 by 6 No. 2 Structural Light Framing exterior studwalls; a No. 2 Stress-rated Board 2 by 4 studwall will exceed the load-bearing capacity of a full-sized 2 by 4 Stud grade exterior studwall by approximately 19 percent. Finally, field evaluation confirmed that when limited wane was allowed, the reduced thickness stud, offered adequate nailing surface for drywall and exterior panel products.

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