A Guide for Placing Control Joints in CMU Tutorial

Movement joints are constructed within masonry to accommodate predicted volume changes of the masonry materials as well as relative movement between masonry and adjacent materials. Movement joints are finished with sealant to prevent water entry while the joint changes dimension. Masonry movement joints may be described as one of three types: expansion joints, contraction or control joints, and isolation joints. Control joints (CJs) are used to accommodate volume shrinkage of concrete masonry, including cast stone. According to the National Concrete Masonry Association (NCMA), concrete masonry undergoes irreversible volume shrinkage over time. Most of the size change occurs during the first year after manufacture. As the concrete masonry decreases in size, or volume, the movement (control) joint increases in width. The sealant in the movement (control) joint needs to be capable of continuing to function as intended, by remaining adhered to the joint sides without internal tearing, while being stretched.