Masonry Shear Wall Strength Design Factors

Footings

• Like any wall designed for stability, masonry shear walls require underground footings that provide much of the support for the above-ground structure. A number of factors determine the strength of these footings in a masonry shear wall. Generally speaking, the deeper the wall footings, the stronger the wall. Like the upper portion of the walls, masonry shear wall footings use concrete and metal rebar pieces to create a solid base for the wall.

Concrete

• Since several materials are mixed together to form concrete, not all concrete performs the same. Adding more sand to portland cement, for instance, creates a drier mix, while using less sand creates a wetter mix. Both of these mixing styles have specific purposes but perform differently in masonry shear walls. Another major component of concrete strength is the use of an additive instead of water. Though they cost more, concretes made with additives hold up better.

Wall Thickness

• The thickness of a masonry shear wall determines both the strength of the wall and the insulating properties of the wall. Thicker shear walls provide more stability and insulation than thinner shear walls. Local building codes generally determine the appropriate thicknesses for masonry shear walls. As a building gets higher, the required width of the masonry shear walls in the building increases. Usually, the masonry shear walls in a building remain a uniform width throughout to ensure consistent performance.

Rebar

• Since rebar forms the inner structure of a masonry shear wall, the placement and amount of rebar used in the wall has a major impact on the durability of the structure. Rebar must be laid both vertically and horizontally within the concrete to provide adequate support. Like with wall thickness, building codes dictate the amount of rebar used to support masonry shear walls. These codes also specify the distances between and placement of metal rebar.