Masonry facades

While a small fire of low intensity will have little effect on a wall other than cosmetic damage, a more intense and prolonged incident will cause expansion and probable cracking, spalling and bulging. The effects will depend on the materials used, their thickness and other factors such as the degree of restraint. Loss of mortar bond is quite possible. (Repairing brick and block masonry, BRE Digest 359, 1991)

Clay bricks are burnt during their manufacture so will usually respond reasonably well to fire. If temperatures are very high, some vitrification of the clay can occur. Concrete and calcium silicate bricks are not exposed to the same temperatures during manufacture and can suffer more harmful effects such as spalling and delamination.

The main risks to masonry arise as a result of structural components that are built into or bear upon it. Steel frames can distort significantly and disrupt masonry, while other components such as galvanised plates, wall ties and the like can lose their corrosion protection. Plastic wall ties, although relatively unusual, can be destroyed.