Deflection

Deflection is the temporary bending of roof or wall cladding that occurs under load when the material is subjected to forces within its elastic limits.

Deflection under distributed load is a voluntary limit of wall cladding, deformation causing residual deflection after application of point load is a serviceability failure of roofing.

Temporary deflection under load is not considered for roof load tables as it has not been found to affect weathertightness. Temporary deflection under load of wall cladding is a recommended limitation for aesthetic reasons, but it is not mandatory.