Modular (standard size) blocks are usually about 7 5/8 inches high by 15 5/8 long in order to allow for?

Modular blocks are designed with specific dimensions to facilitate efficient construction and ensure uniformity in building practices. The height of 7 5/8 inches and the length of 15 5/8 inches are intended to create a standard unit that takes into account the thickness of mortar joints when the blocks are laid.

In standard masonry construction, the typical mortar joint thickness is generally around 3/8 inch. This is why the dimensions of the modular blocks are slightly larger than the nominal values, to accommodate this mortar joint. When the blocks are laid with 3/8 inch mortar joints, they will align perfectly, maintaining a consistent modular dimension across the wall.

This allowance for mortar ensures that when calculating the total height or length of a wall, the effective dimensions reflect both the blocks and the mortar used in between. Therefore, the use of 3/8 inch mortar is ideal for achieving the overall desired sizing in modular masonry construction.