The standard sizes are 4,6,8,10, and 12" CMU's. In addition to the “standard” sizes 16" is custom order. Concrete brick is available in typical lengths of 8 and 16 in. (203 and 406 mm), nominal 4 in. (102 mm) width, and a wide range of heights. They may be 100% solid, or may have two or three cores. Like ASTM C 90, Standard Specification for Concrete Building Brick, ASTM C 55 (ref. 4), permits overall unit dimensions to vary +1/8 in. (3.2 mm) from the dimensions specified by the manufacturer. Nominal dimensions of modular concrete brick equal the actual dimensions plus 3/8 in. (9.5 mm), the thickness of one standard mortar joint. However, nominal dimensions of nonmodular sized concrete brick usually exceed the standard dimensions by 1/8 to 1/4 in. (3.2 to 6.4 mm).
Standard Specification for Load-Bearing Concrete Masonry Units, ASTM C 90 is the most frequently referenced standard for concrete masonry units. ASTM C 90 includes minimum face shell and web thicknesses for the different sizes of concrete masonry units. Overall unit dimensions (height, width, or length) are permitted to vary by +1/8 in. (3.2 mm) from the dimensions specified by the manufacturer. Where required, units may be manufactured to closer tolerances than those permitted in ASTM C 90. ASTM C 90 also defines the difference between hollow and solid concrete masonry units. The net cross-sectional area of a solid unit is at least 75% of the gross cross-sectional area.
