How much is the effective thickness of an 8" nominal block after accounting for mortar joints?

The effective thickness of an 8" nominal block, after accounting for mortar joints, is 7-5/8 inches. In construction, nominal dimensions refer to the stated size of building materials, such as blocks, prior to any finishing or installation processes.

For concrete masonry units, the actual size is typically smaller than the nominal size due to the thickness of the mortar joint that is used during installation. A standard mortar joint is usually around 3/8 inches thick. When you subtract the total width of the mortar joints from the nominal width of the block, the calculation is as follows:

1. The nominal dimension of the block is 8 inches.

2. With a mortar joint on the top and bottom, you need to account for 3/8 inches for the joint above and 3/8 inches for the joint below, which totals 3/4 inches (0.75 inches).

3. Subtracting that 0.75 inches from the nominal dimension: 8 inches - 0.75 inches = 7.25 inches.

In fractional terms, 7.25 inches converts to 7-5/8 inches. Therefore, this is why the effective thickness of an 8" nominal block,