Racking Strength of Walls Sheathed with Structural Flakeboards Made from Southern Species

Ten types of structural flakeboards and two types of southern pine plywood were evaluated. Racking loads were applied to full-size racking panels (8 by 8 ft., according to ASTM E 72) and small panels (2 by 2 ft.). When subjected to a 1,600-pound racking load, 8- by 8-foot panels sheathed with flakeboards containing a mixture of hardwood and pine flakes were slightly stiffer than southern pine plywood (0.10-in. vs. 0.12-in. deflection). Yet, plywood-sheathed panels provided slightly higher strengths for the full-size racking test (6,000 lb. vs. 5,500 lb.). The highest average racking strength, 6,200 pounds, was obtained with the 1/2-inch yellow-poplar- sheathed panels. After a 24-hour water soak, small panel racking resistances and lateral nail strength decreased. The racking strength decrease ranged from 4 percent (5/8-in. oriented mixed high density) to 18 percent (1/2-in. oriented mixed low density). All panel types had racking strength reductions within limits allowed under current standards. The nail strength decrease ranged from 9 percent (5/8-in. random mixed high-density flakeboard) to 27 percent (1/2-in. southern pine plywood). Theoretical racking strengths (derived from a linear mathematical model based on lateral nail resistance) were close to, but consistently higher than, test values.

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