Side Story: Hollow Brick: 101


April 2009


How well do you understand hollow brick? Traditionally, the size and number of holes in a brick unit have varied, based on manufacturer capabilities, the type of clay being extruded, the type of firing process, and the intended use of the product. These various hole patterns were categorized into two basic designations: solid brick and hollow brick. Solid brick are defined as having holes (or voids) not greater than 25 percent of the unit’s bed area. Hollow brick are defined as having greater than 25 percent and, at most, 60 percent void areas. Hollow brick are further classified into those with a void area not greater than 40 percent and those with greater than 40 percent voids. In today’s construction, the majority of hollow brick produced is used in two basic applications.

The first is in reinforced or unreinforced, single-wythe structural walls. Hollow brick units provide both the structural component and the brick finish without the need for additional materials. Hollow bricks for this type of use generally range in size from four to eight inches in nominal thickness, with void areas in the 35 percent to 60 percent range. Typical, single-wythe applications of hollow brick include commercial, retail and residential buildings; hotels; schools; noise barrier walls; and retaining walls. The second application of hollow brick is as veneer units. These bricks are generally three to four inches in nominal thickness, with void areas typically between about 26 percent and 35 percent (source: Brick Industry Association Tech Note 41).

The decision to incorporate this material could mean a savings of the both material and fuel used to make the bricks. Pollutants are reduced during the firing of the bricks, and shipping the material is cheaper, due to a reduced weight. You can keep up with changes in the specs and characteristics of hollow brick and all brick materials by visiting


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