What is the minimum thickness range for the bed joints of the second masonry course?

What is the minimum thickness range for the bed joints of the second masonry course?

• A. 1/8 inch to 1/4 inch
• B. 1/4 inch to 1/2 inch
• C. 3/8 inch to 5/8 inch
• D. 1/2 inch to 3/4 inch

Answer: (B)

Bed joints are the horizontal mortar layers that bond masonry units from one course to the next. For the second masonry course, you need enough mortar to develop a solid bond with the first course, but not so much that the units can’t be laid true or the joint becomes weak from excessive shrinkage or misalignment. The allowable range that balances these concerns is about a quarter inch to a half inch. A joint much thinner than that risks a poor bond and weak shear transfer; a joint much thicker than that can cause alignment problems, excess mortar squeeze-out, and added shrinkage issues. So the minimum practical thickness is 1/4 inch and the maximum practical thickness is 1/2 inch.

Bed joints are the horizontal mortar layers that bond masonry units from one course to the next. For the second masonry course, you need enough mortar to develop a solid bond with the first course, but not so much that the units can’t be laid true or the joint becomes weak from excessive shrinkage or misalignment. The allowable range that balances these concerns is about a quarter inch to a half inch. A joint much thinner than that risks a poor bond and weak shear transfer; a joint much thicker than that can cause alignment problems, excess mortar squeeze-out, and added shrinkage issues. So the minimum practical thickness is 1/4 inch and the maximum practical thickness is 1/2 inch.