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Cavity Wall Tie Failure

Since the 1920's, most properties in the UK have been constructed with the main walls incorporating a cavity. A cavity helps reduce the risk of damp penetration and improves insulation standards. The two leaves of the cavity wall, which are usually of brick or blockwork are held together by ties, which provide additional stability to the wall. Usually these ties were of metal. With age these ties tend to corrode and fail causing the inner and outer leaves of the wall to become unconnected and therefore unstable.

If the problem is not identified and dealt with, horizontal cracks may be the first external signs of a problem, but corrosion can continue without external evidence. Older types of cavity ties can rust and expand causing movement and bulging of masonry, and possible eventual collapse in high winds.

Improved galvanising processes were introduced in 1981 and properties built before this date are generally at greater risk to wall tie corrosion. Some types of mortar can be more corrosive and the type, height and location of a property can affect its vulnerability. Sometimes properties are constructed with insufficient wall ties. Research by the BRE (Building Research Establishment) has indicated that up to two million dwellings suffer from cavity wall tie corrosion or failure.

Surveyors look for evidence of deterioration or failure and will normally have local knowledge of this type of problem. When suspicions are aroused, a surveyor is likely to recommend closer examination of the cavity ties using an endoscope (a small optical instrument which is used to view the interior of the cavity) so that the extent of any problem can be assessed.

Specialist companies carry out remedial work to replace cavity wall ties and since this work can largely be carried out externally there is minimal disruption and damage to the interior of the property. These contractors can usually provide a guarantee in respect of their work.