Control Joints

Control joints are vertical separations built into a concrete masonry wall at locations where stress concentrations may occur. They are one method used to relieve horizontal tensile stresses due to shrinkage of the concrete masonry units, mortar, and when used, grout. Control joints reduce restraint and permit longitudinal movement. Control joints should be located where volume changes in the masonry due to drying shrinkage, carbonation, or temperature changes are likely to create tension in the masonry that will exceed its capacity. Care should be taken to provide joints at locations of stress concentrations such as: at changes in wall height, at changes in wall thickness, at movement joints in foundations and floors, at movement joints in roofs and floors that bear on a wall, near one or both sides of door or window openings, adjacent to corners of walls or intersections within a distance equal to half the control joint spacing.