What is the maximum size of a bed joint in a masonry wall directly on the foundation?

• A. 1/2 inch
• B. 1/4 inch
• C. 3/4 inch
• D. 3/8 inch

Answer: (C)

Bed joints are the horizontal mortar layers that bond bricks or blocks in each course. When a masonry wall sits directly on a foundation, keeping this first joint from becoming too thick is important for solid bearing and a continuous bond. If the joint is too thick, mortar can slump, the bond quality drops, and load transfer to the foundation becomes less reliable, increasing the risk of cracking and misalignment as the wall settles. Limiting the bed joint thickness to 3/4 inch provides enough mortar to fill small irregularities in the foundation and create a stable bearing plane, while still maintaining a strong, well-bonded connection. So, the maximum size is 3/4 inch.