A nailed sheathing-to-lumber joint may fail in one of two possible modes when subjected to a load applied along the axis of the fastener: shank withdrawal from the lumber and nailhead pull-through of the sheathing material. Under certain circumstances, such as strong gusts of wind, hurricanes, or seismic activity, shingles or siding may be loosened or detached as nails are withdrawn. Alternatively, these lifting forces may pull roof or wall panels through nailheads. In either circumstance, the integrity of the structure may be severely impacted.

APA has conducted more than 1,900 tests on wood structural panels (plywood and OSB) of different thicknesses using three different types of nails under three different exposure conditions to investigate the effect of these variables on nail withdrawal strength. I discussed this test program and the results in a paper presented at the 9th World Conference on Timber Engineering in August. A summary is below. Look for APA’s other conference presentations to be posted on the Blog soon.

APA’s extensive test program was conducted to develop nail withdrawal design values for wood structural panels. Tested variables included: nail type (plain shank vs. deformed shank), panel type (plywood vs. OSB) and thickness, and exposure condition. Based on the test results, the recommended allowable nail withdrawal strength for plywood and OSB panels, expressed as an equivalent specific gravity, is 0.40 for plain or screw shank nails and 0.70 for ring shank nails. A wet-use adjustment factor of 0.75 is recommended for applications subject to wet-service conditions. In a separate study, APA evaluated the nailhead pull-through strength of wood structural panels. While nailhead pull-through strength might not be considered in most designs, the results presented in this paper can be used as a reference in evaluating nailhead pull-through performance of wood structural panels.

Download Nail Withdrawal and Pull-Through Strength of Structural-Use Panels for more information on the objectives and results of this test program. Read more about the 2006 World Conference on Timber Engineering.