Wood Structural Panel Shear Walls Installed with Inboard Rigid Foam Insulation
Technical Topic
Wood structural panel shear walls with inboard rigid foam insulation lose lateral shear strength due to reduced nail bearing capacity when fasteners must penetrate the foam layer before reaching framing. This technical publication addresses how to restore code-equivalent shear performance for these assemblies, providing empirically tested nailing solutions backed by full-scale cyclic shear wall testing conducted at the APA Research Center.
This publication is designed for: engineers, designers, builders, code officials
The publication presents full-scale cyclic shear wall test results for 7/16 Performance Category OSB installed with inboard rigid foam insulation, and translates those results into a nailing schedule that achieves seismic performance equivalent to conventional shear walls built without foam. It explains the Seismic Equivalency Parameters (component overstrength, drift capacity, ductility) used to evaluate the test assemblies, identifies which foam/nailing configurations failed to meet equivalency, and provides adjusted design values — including a stiffness reduction factor for deflection calculations — for use where a prescriptive method does not yet exist.
Key sections include:
Background on shear strength reduction from inboard foam insulation
Table 1: nailing requirements for intermittent wall bracing (WSP method) with inboard foam
Table 2: allowable shear capacity for Douglas-Fir-Larch shear walls with inboard foam
APA full-scale cyclic shear wall test program and Table 3 test matrix
Seismic Equivalency Parameters and test results by assembly configuration
Conclusions on required nail length/spacing and shear stiffness adjustment
Workmanship guidance on slant nailing with foam-thickened assemblies
Published by APA — The Engineered Wood Association.
Published by APA — The Engineered Wood Association.
