Masonry facades

While problems with brick slips led to their decline in popularity, a failure to accommodate movement also affected brick panel construction, leading to some significant failures. In extreme cases, expansion of the brick coupled with contraction of the frame led to fracturing of brick support knibs or, and more commonly, distortion in the brick outer leaf, leading to bowing and in some cases loosening of the brickwork.

A common problem is the excessive overhanging of bricks at the bottom edge of the panel. The maximum overhang of the brick over the panel should be no more than one third of the thickness of the brick - for example, with 102mm bricks, a maximum of 34mm. However, inaccuracy of construction can lead to parts being rather more than 34mm - perhaps up to 50mm or more. This eccentrically loads the bricks and coupled with the effects of expansion can lead to the bowing and loosening of the bottom courses of brickwork.

The effects of expansion in a brick panel can be significant, particularly if the joint between the frame and the panel is unable to accommodate it. Movement of as little as 0.5mm in a 3,000mm panel can cause the panel to bow out of plane by as much as 25mm at mid span if the ends are restrained. (Why do buildings crack?, BRE Digest 361, 1991)

Deflection of floor slab rotates edge beam and disrupts brick cladding