Shear walls are wall systems that transfer lateral wind and seismic loads from a roof or floor down to lower levels, and then into the foundation. Under prescriptive design codes for conventional construction, shear walls are referred to as braced wall panels. Braced wall panels serve the same function and have very similar detailing as some shear wall assemblies; however, the term “shear wall” is most frequently associated with an engineered structural system.
Wood structural panel (WSP) sheathed shear walls are the most common shear wall system used in engineered wood-frame buildings. The construction requirements and load capacities of WSP sheathed shear walls are found in the American Wood Council’s Special Design Provisions for Wind and Seismic (SDPWS). In older versions of the IBC and other model building codes, the allowable shear strength of different shear wall assemblies were found in different areas of the model building code; however, they are now located together in the SDPWS document.
Generally speaking, wood shear walls become stronger with thicker sheathing, tighter connector spacing, and larger connectors. High-strength wood shear walls can be double-sided with WSP sheathing on each side and are sometimes required to have framing members larger than typical 2x nominal sized lumber.
There are three types of engineered WSP sheathed shear walls recognized in the SDPWS and in common use:
- The segmented shear wall approach uses full-height shear wall segments with no openings, each with full end restraint against overturning.
- The “force transfer around openings” (FTAO) approach utilizes strapping to transfer forces around openings.
- Perforated shear wall method provides a way to account of the strength and stiffness of shear walls with openings while providing an alternative to the strapping used around openings typically required in other methods.
In addition to the SDPWS-recognized shear wall types, several component manufacturers have pre-manufactured shear wall products intended for use in wood construction. These are not explicitly recognized in the building code and referenced standards. However, manufacturers frequently have code evaluation reports that are reviewed and published by third-party evaluation services to demonstrate that the products meet the intent of the building code when used according to the manufacturer’s instructions and the evaluation reports.