Control joints or articulation joints are full-height vertical separations built into the brick work allowing brick separation.This is to accommodate limited differential movement,generally caused by seasonal affects, thereby protecting the wall from unwanted cracking.
They may be present in the middle of a continuous wall, or before a corner. They are either within the wall or placed alongside windows or door openings in an attempt to conceal their presence. They are meant to allow movement but maintain the weatherproof function of the masonry cladding protecting the building.
When these joints widen outside of tolerance, the degree of differential movement has likely exceeded the design limits of the building and the cause of the foundation failure should be addressed. There may be associated signs of distress farther along the wall away from the joint such as cracks in the brick work or internally within the plaster, which indicate the origin of the settlement influencing the control joint appearance.
Alternatively, control joints can close up at top, compressing the flexible sealant and causing adjoining brick panels to become impacted. This develops when the position of the control joint along the wall becomes lower than the adjacent sections of wall. If the degree of variation is significant enough, cracks may form in the brick work higher on the wall around the control joint due to interference as the panels lean in toward each other. Cracks with vertical displacement can also develop closer to the ground through the relative absence of foundation support allowing suspended bricks to drop.