What is the acceptable vertical tolerance allowed in CMU and brick construction?
1/8\" in 10ft and 1/4\" in 20ft?
Acceptable vertical tolerances in cmu and brick are covered in TMS 402/602 Building Code Requirements and Specification for Masonry Structures. The specific location is TMS 602 Part 3 paragraph 3.3 F.2.b. It allows for a +/-1/4" in 10 lf, +/- 3/8" in 20 lf and a 1/2" maximum. Remember when checking these tolerances that the TMS 402/602 may not be the best from an atheistic standpoint. The architect can put tolerances in the project specification that are more stringent than given in the code. They may also reference documents from BIA or NCMA. Read your specifications very carefully to insure that what is stated in the specifications won't require workmanship of a higher level (more costly). Brick workmanship should always be approved using a mockup.
Remember!! There is no ASTM standard for acceptable masonry workmanship.
The "STC" or Sound Transmission Class of a brick can vary based on thickness, hollow or solid, and textured finish among other things. The Masonry Society has a publication called TMS 302 Standard Method for Determining the Sound Transmission Rating for Masonry Walls. It helps calculate the STC of a wall. There is a BIA Technical Note # 5A. It describes a typical 4" brick as having a STC of 45. The best way to determine the STC of brick is to contact your local brick distributor. They should be able to give you the value of the specific brick you want to use.
Jerry Painter, FASTM
Don Beers, PE, GC
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