Applied exterior finishes

Cracking within the surface finish can result from a number of causes. Aside from the obvious structural faults, the effects of moisture and temperature movements in the background could induce stresses within the finish which can only be relieved by cracking or delamination. Long term creep within a concrete structure can induce stresses within a tile finish unless adequate provision for movement is made.

Movement joints should be at least 3-4m vertical centres and be at least 6mm in width. They should also pass through the tiles, the intermediate background and where required to the background itself. Joints should also occur at changes in background material and coincide with main movement joints.

Dark coloured finishes absorb heat and exacerbate thermal movements that must be accommodated by the provision of joints. A 4m wide concrete panel with a dark finish could have as much as a 4mm range of movement.

The formation of cracks permits water ingress with subsequent risk of frost attack, chemical reactions and also localised carbonation of concrete backgrounds (which could then permit steel reinforcement bar corrosion).