Cavity wall ties are used to tie the internal and external leafs of brickwork together. Original wall ties would have been placed into the mortar joints of a cavity wall during construction.

Cavity wall tie corrosion or failure arises due to moisture penetration into the outer leaf of brick work. Prior to the 1930`s cavity wall ties were not galvanised and therefore offered no protection against corrosion. Between 1964 and 1981 the British Standard for weight of galvanising was actually reduced, which has since been found to be inadequate, offering a substandard level of protection.

The location of a property or elevations that are more exposed to driving rain can also affect the potential for wall tie corrosion.

Moisture penetration into the masonry causes the wall tie to corrode, this eventually leads to expansion of the wall tie. In some cases more than three times its original size.

The most recognisable symptom of cavity wall tie corrosion is horizontal or stepped cracking of mortar joints, generally at regular intervals to an affected elevation. This can, if not remedied, lead onto outward bulging of masonry and internal cracking of plaster. At worst can cause structural weakness and/or collapse.

After an initial inspection is undertaken, a course of remedial action will be proposed. A variety of stainless steel wall ties are available, from mechanical, resin, or drive in (dry-fix). The specific wall tie required will be assessed on the condition of the masonry involved.

New wall ties will be installed at regular pre-determined intervals. Original wall ties will generally then require isolation from the outer leaf of masonry. This may in some cases involve protective PVC coverings being installed.