Question: Do the tolerances listed in the Masonry Standards Joint Committee Specification for mortar joint thickness (Article 3.3 F.1.b in the 1995 edition or 3.3 G.1.b in the 1999 edition) apply to single-family residential construction?
Answer: The tolerances listed in the MSJC Specification do not generally apply to residential construction. The CABO one- and two-family dwelling code also includes tolerances for mortar joint thicknesses in 605.1.1.1. These tolerances are identical to those in the MSJC Specification. These tolerances do not apply to nonloadbearing masonry (including veneers). They do, however, provide some guidance to judge the quality of masonry work in residential construction, even if they are not considered a code requirement. The permitted variations in mortar joint thickness in CABO and the MSJC Specification are ± 1/8 inch for bed joints and +3/8 inch, -1/4 inch for head joints.