Installing joints is the most effective way to control cracks in masonry. There are three types of movement joints: control joints, expansion joints, and isolation joints. Concrete masonry should be constructed with control joints. Clay masonry should be constructed with expansion joints. And when necessary, isolation joints should be used in both types of masonry. INSTALL CONTROL JOINTS IN CONCRETE MASONRY A control joint is nothing more than a predetermined, straight crack in concrete masonry. The strategy of combining joint reinforcement, bond beams, and control joints has been the most effective way to control shrinkage cracking in concrete masonry. Control joints also must be designed to transfer lateral wind loads from one side of the joint to the other. Usually sash blocks and shear lugs are used at control joints for this purpose. INSTALLING EXPANSION JOINTS IN CLAY MASONRY Clay brick generally expands as it absorbs moisture or freezes. To accommodate this, expansion joints must be installed. An expansion joint provides space for the brick to move when its volume increases. The width of the joint is critical. If the joint is too narrow or if dirt in the joint prevents movement, huge compressive stresses can build up and crush the brick. The amount of expansion is affected by the temperature of the brick when it is installed, by creep and shrinkage potential of the backup material, and by the amount of insulation behind the brick. ISOLATION JOINTS Isolation joints are installed wherever masonry abuts other building materials or wherever new masonry abuts existing masonry. An isolation joint breaks the bond between the masonry and the other material and allows the two to contract and expand independently.