Applied exterior finishes

Background failure is most likely to be as a result of chemical problems such as sulphate attack within brickwork. If unsuitable materials are used, soluble sulphates can be dissolved by water ingress behind the finish. These sulphates may then react with water to form ettringite at the interface of the background and the rendering finish, with subsequent spalling together with expansion of the brick joints.

Similarly, the effects of reinforcement corrosion can cause spalling of render and tile finishes, the expansive forces generated being sufficient to push off applied finishes.