SHEAR WALLS

WHAT THEY ARE AND WHY WE CARE

Written by Okkem Design

Shear walls are specially designed and strategically placed wall segments that enable structures to resist lateral, or sideways, loads such as those from earthquakes or strong winds. A shear wall's ability to resist these forces relies on two key attributes: in-plane stiffness, which helps it stay rigid when pushed from the side, and rotational fixity, which keeps it firmly anchored down and prevents it from tipping or pivoting over its corners.

In residential construction, in-plane stiffness is typically achieved by attaching plywood or a similar sheathing material to every stud in the shear wall segment. The thickness of the sheathing, as well as the type and spacing of fasteners, is carefully selected and specified by a structural engineer to ensure that in-plane forces are effectively transferred through the wall with minimal in-plane deflection or 'racking' (see Fig. 1). Rotational fixity is typically achieved by connecting the bottom corners of the shear wall to the framing members or foundations below using commercially available metal connectors called "hold-downs" (see Fig. 2).

Figure 1: Racking

Figure 2: Rotation

All residential structural drawings should specify the length and location of shear walls, their sheathing material and thickness, the type, size, and location of hold-downs, and all relevant fastener types, spacings, and sizes. This information is typically included in the Shear Wall Plan, Lateral Bracing Plan, Wind Bracing Plan, or other similarly titled drawings. If no shear walls are specified in the drawings, it could mean that an alternative lateral force-resisting system is being proposed. In any case, the proposed system must be identified, understood, and correctly implemented by the builder.

If you have any questions about your project's lateral force-resisting system, please don't hesitate to reach out and schedule a free consultation with one of our design professionals.