The performance of the cavity wall
The strength of the wall is gained from the tie between the two leaves of the outer and inner walls. The outer leaf protects the interior of the building, and provides the decoration and weather resistance ot the exterior of the property. The loads imposed on on the internal leaf are distributed through the wall, as long as the wall ties are in good condition. Any variation in the relationship between these two leaves will lead to the wall acting as two single leaves and not as a unit. The failure of the wall tie will affect the performance of the wall. Not only will the leaves act independently because they are no longer linked together, but also the corrosion of the metal of the tie may distort the wall and cause loads to be applied concentrically. The load may fall on the inner leaf, or at an angle to the inner leaf, resulting in an overturning moment, which can lead to the failure of an already weakened wall.

Loading
The cavity wall performs in a specific way. The loads of internal floors and roof are supported on the inner leaf of the wall, but because of the link between the two leaves of the cavity, it is the complete wall which carries the load. The weight on the inner leaf is redistributed on to each leaf, so that the load strikes the foundations around the centre line of the cavity wall. The failure of the wall to act as a unit will lead to foundations being loaded concentrically, because the load is applied to half the wall. If the foundations were under strength, this may place too great a strain on them and lead to failure. If the foundations have deteriorated, or were undersized, this redistribution of the load applied to them may lead to a more serious failure.

The result of tie failure
Instability
The wall components may become loose and fall from the face of the building. Lightweight cladding on the face of a structure is more likely to fail when placed under stress by high winds.

Redistributed load
The failure of the metal tie reduces the strength of a cavity wall and may result in the collapse of a structure if the redistributed load is beyond the capacity of either leaf. The tie failure will mean that each leaf will act independently, making them more vulnerable if either leaf has to take all the load.