Movement joint (expansion joint)

A movement joint (also called an expansion joint) is a deliberate gap designed into a building element so it can expand and contract with temperature and structural movement without cracking or buckling. Materials grow and shrink as they heat and cool, and in Dubai the swing between a 50°C facade in the sun and a cold, AC-chilled interior — plus day-to-night and seasonal ranges — makes that movement large. So curtain walls and aluminium facades, big tiled floors and terraces, long runs of blockwork, and screed all need movement joints at planned intervals, filled with a flexible sealant (not rigid grout or mortar) so the gap can open and close. It's different from a control joint, which is cut into concrete to make any inevitable crack happen along a neat chosen line. Skip or wrongly fill movement joints and you get the classic Dubai failures: tiles that 'tent' and pop off a terrace, cracked grout lines, buckled cladding, and failed perimeter seals. Sealant makers such as Sika publish the movement-joint systems used here. Getting the joint spacing and the right flexible sealant is specialist work for an aluminium and metalwork specialist in Dubai or a tiling/waterproofing pro, not something to caulk over with whatever's in the tube.