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Wall Tie Corrosion

old brick wall

I find that I have been writing short articles for Sussex Local’ for some 10 years… Doesn’t time fly! I recall that the first such article concerned cavity wall tie corrosion issues, so I thought it would be about time to revisit the topic.

In the Middle Ages walls were as often as not formed around a structural timber frame with infill panels constructed in either brick flint or other locally sourced materials. Until circa 1900 walls were of mainly solid construction and thereafter modern property was more normally constructed with cavity brick or block walls.

A cavity wall is constructed with two skins of brick or block work with a ‘cavity’ between them. This cavity serves to minimise the likelihood of water penetration through the wall, and adds to the insulation qualities of a building.

Chris Ennis, Property Doctor, Chartered Surveyor
Chris Ennis, Property Doctor

One of the frequent problems associated with cavity walls is ‘wall tie failure’. Wall ties are the metal strips which adjoin the inner and outer skins of brickwork together. They commonly rust and disintegrate and can cause horizontal and diagonal fractures to occur in brickwork. Many of the properties I inspect are, or have been affected to some extent by this very
common defect.

There are many forms of wall tie… Early designs may have been constructed in cast iron, but more modern equivalents include twisted wire, galvanised metal and more latterly, stainless steel. I recall that on one occasion during a demolition we came across a ‘tie’ that was formed using a sardine can opening key…probably laid by a brick layer having just finished his lunch.

When the wall ties rust, they expand in size and cause the characteristic horizontal and diagonal cracking clearly seen on many 1920/1930 properties. In extreme cases the cracking can elevate the walls and roofs to produce what we call the ‘pagoda’ effect which is visible on the gable ends of affected walls. There have been instances in Worthing, where walls have been unstable to the point of imminent collapse.

If you live in a property with cavity walls, examine the external surfaces on the south and west elevations…. If you notice cracking, call me and I can put you in touch with a local contractor who can solve the problem.

Chris Ennis FRICS is a Chartered Surveyor Tel: 01903 261217 email: surveyor1@talktalk.net www.propdoctor.co.uk