What are Cavity Wall Ties?
Cavity walls have existed for many years but during the 1930’s and in subsequent years it became popular to use zinc galvanised ties to hold the two leaves of brickwork together. Often the zinc galvanised coating has deteriorated over the years, exposing the steel inners which are vulnerable to corrosion.
Metal detectors are used to locate the old troublesome ties. With an endoscope the surveyor can check the condition of the old tie.
Wall Ties ensure the stability of a cavity wall structure, tying its weather protecting, brick facade to the main body of the structure.
How to identify Cavity Wall Tie failure
- Horizontal Cracks – in mortar, often a high level, caused by expansion of corroded wall ties.
- Bulging brickwork – caused by snapped wall ties, which have corroded. This can make your property unstable.
- Lintels sagging
- Cracks or separation of window reveals
The use of black ash mortar is also known to accelerate this corrosion. A thorough investigation and wall tie survey is essential.
Cavity Wall Tie Replacement
Having diagnosed the presence of broken or corroded ties, the surveyor will then decide upon the most appropriate replacement tie system.
This may include isolation of the existing wall ties from the outer wall using an expanding foam, removing the ties completely from the wall or indeed no action at all. This will all depend on the type of existing tie and their condition. The property will be re-tied using stainless steel drill ties. This is usually at a density of 2.5 ties/m2 overall with additional ties at the sides of openings.