Distress of cavity walls is sometimes attributable to corrosion or absence of the metal ties. BRE research has shown that steel ties made before 1981 could corrode prematurely. Generally the wall bulges, cracks or leaks, but if subjected to high wind loads it might even collapse.

This Guide shows how to assess masonry wall ties and, when appropriate, how to replace them. It summarises guidance given in more detail in other BRE publications, covering what to look for (several photographs from IP13/90 illustrate typical cracking patterns on a smaller scale than in the IP), how to assess the extent of damage and decide whether replacement is necessary, and how to replace the corroded ties with resin-glued ties or expanding stainless steel ties.