Although a size not listed in the table might be desired for a specific project, special sizes are typically avoided where possible in order to not increase costs unnecessarily. The use of the specified dimensions when ordering and specifying brick is strongly recommended, since a brick name can vary from manufacturer to manufacturer, and a non-modular brick will not have nominal dimensions. To avoid confusion, specify brick using the stretcher position with width first, followed by height, then length. In other words, a modular brick would be specified as 3 5/8 in. x 2 ¼ in. x 7 5/8 in. (92 mm x 57 mm x 194 mm).
There are relationships between width, height and length of brick that were developed as brick masonry construction began. The most common of these dimensional relationships are:
- Two brick widths plus one mortar joint equal one brick length, and
- Three brick heights plus two mortar joints equal one brick length.
Use of these relationships allow corners and openings in brick walls to be constructed with little waste and limited cutting of brick. These relationships allow rowlocks and headers to tie adjacent wythes together and courses of brick in different orientations to align vertically. This has given rise to the rich variety of detailing that is part of the architectural vernacular of brickwork.
Because of greater ease in design and construction, the vast majority of contemporary brickwork uses modular-sized brick and modular dimensioning. The most common modular dimension system for brickwork utilizes a 4 in. (102 mm) grid. The 4 in. (102 mm) grid is used in modular coordination between the brick and concrete masonry units and fits the modular dimensions of other construction materials.