Concrete masonry units, commonly known in the building trade as CMU, are
structural units made with cement and fine aggregate and most often used in
commercial buildings, retaining walls, fences, planters, etc. The holes or cells in
the block are used for the placement of reinforcing steel (rebar) horizontally and
vertically and then concrete is poured into the cells to create a formidable
Blocks typically come in several sizes:
6”x8”x16” commonly used for small planters, perimeter fences 6’ high
8”x8”x16” commonly used in commercial buildings
12”x8”x16” sometimes used in commercial buildings where extra support is
needed and also retaining walls.
When designating the size of a unit, the width is the first number, then the height,
and lastly the length. In the examples above the height and length are all the
same but the width of the block is the variable according to the building need. To
be sure there are other sizes of block but these are the most common.