A mortar joint's size depends on the material and application, but the most common size is 3/8 of an inch (0.38 inch). This is specified by International Building Codes TMS 602 in the “Specifications for Masonry Structures.” A 1/2 inch (0.5 inch) joint is also frequently used.
Common Mortar Joint Sizes:
- 3/8 inch (0.38 inch): This is the standard and most widely accepted size for many masonry applications.
- 1/2 inch (0.5 inch): Another frequently encountered size, often used alongside the 3/8 inch standard.
- Other Sizes: While less common, mortar joints can vary depending on factors such as the type of masonry (brick, stone, block), the structural requirements, and aesthetic preferences. Joints significantly larger than 1/2 inch are generally considered excessive and may indicate issues with the construction technique or material choice. For example, joints of 1-1/2 inches or larger are often cited as signs of poor workmanship. Smaller joints, while sometimes used for specific aesthetic reasons, can be challenging to work with and may affect the structural integrity of the wall. Block joints, for instance, are theoretically around 10mm but often larger in practice.
Factors Affecting Mortar Joint Size:
The optimal mortar joint size is determined by several factors including:
- Material type: The size of the mortar joint will vary depending on whether it’s for brick, stone, or concrete block.
- Structural requirements: Load-bearing walls may require narrower joints for increased stability.
- Aesthetic considerations: The desired appearance of the finished wall can influence joint size.
Importance of Proper Mortar Joint Size:
Proper joint size is critical for the strength, durability, and overall integrity of the masonry structure. Excessively thick joints can weaken the structure, while excessively thin joints may be difficult to tool correctly. Specifications from sources like the ASCE 6-88 recommend minimum widths of 1/4 inch and maximum widths of 1/2 inch for bed joints in order to ensure both proper tooling and adequate strength.
