What is the standard mortar joint thickness between concrete and masonry units (CMU)?

The standard mortar joint thickness between concrete and masonry units (CMU) is typically 3/8 inch. This dimension is commonly used in masonry construction because it provides a balance between structural integrity and ease of construction. A 3/8 inch joint allows for adequate placement of mortar while still being narrow enough to ensure the overall strength and aesthetic of the wall.

Using a joint that is too thick could weaken the bond between the blocks or bricks and potentially lead to issues such as cracking or water penetration. On the other hand, a joint that is too thin might not accommodate the necessary adjustment for alignment during construction or could lead to difficulty in achieving proper bonding. The 3/8 inch thickness thus serves a practical function in ensuring that walls built with masonry or CMU are stable, strong, and visually appealing.