In many existing retrofits performed by amateurs one not only finds foundation bolts misinstalled but the plywood as well. The 2013 California Building Code considers it a code violation if the nail heads penetrate the surface of the plywood and this is the rule rather than the exception in cripple wall shear walls in existing retrofits. The American Plywood Association developed ways to address this problem to bring the shear walls back to full strength.
Shear Walls with over driven nails
- If more than 20% of the over driven nails around the perimeter of shear wall are over driven by over 1/16″, or if any are over driven by more than 1/8”, additional nails shall be driven to maintain the required shear capacity. For every two fasteners over driven, one additional nail shall be driven.
- If nails were used in the original installation, and are spaced too close to allow the placement of additional nails, then 3 approved staples must be used for every additional nail required.
Under the following conditions, nothing need be done to address this condition.
- If all nails are over driven into shear wall by up to 1/16” during construction under dry conditions (moisture content less than 16%).
- If no more than 20% of the over driven nails around the perimeter of the shear wall are overdriven by over 1/16″ up to 1/8”, no reduction in shear capacity needs to be taken.