Cavity walls have always presented builders with a unique problem. While the cavity is a vital part of modern household design to not only allow for better insulation but also damp proofing, they can be structurally weak. While the inner wall (or leaf) will typically be supported from inside the house by the various walls and floors attached to it, the same cannot be said for the outer wall. This typically stands alone and therefore without additional support would risk falling over in severe weather.
Cavity wall ties therefore serve to link the weaker outer surface of a cavity wall to the stronger inner wall. In this way both parts of the cavity wall support each other, producing a far more robust overall structure.
So far so good, however there are a number of common problems that can occur with cavity wall ties, depending on the age of the property and how well the cavity wall ties were installed to begin with.
These days, cavity wall ties tend to be made from stainless steel, though some plastic or composite materials are now increasingly used to reduce corrosion. Older houses frequently possess cavity wall ties that are made from far less corrosion-resistant metals. Over time these can therefore begin to rust.
Rust can damage your cavity walls in two ways. Firstly, as might be expected, the rusting metal ties serve to weaken the wall, increasing the chances of your walls bowing out of shape. This can be very dangerous and in more extreme cases has even been known to result in the outer wall of houses falling down completely.
The other risk that rusty cavity wall ties pose is that as the rust progresses, so the wall tie expands. This in turn can cause further damage to your wall, damaging mortar and in some cases causing cracks to appear in the brickwork.
A second problem sometimes seen in cavity wall ties, which is less frequently experienced though no less serious, is where cavity wall ties have been improperly installed to begin with. In some cases, even on new-build properties, wall ties that are too short have been used – or cavity wall ties of the correct length have not been properly embedded in the wall.
As can be seen from the above descriptions, problems with cavity wall ties can be very serious indeed and, if left unchecked can be very troublesome to repair. It is better to act as quickly as possible if you have your suspicions so that remedial work will be both easier and cheaper to complete.
So what can you expect from a cavity wall tie expert? The first step is to carry out a detailed survey of your property. Many common problems with cavity wall ties are easily observable with the naked eye simply by examining the outer brickwork of a property.
However to gain a deeper insight it is customary to drill a small hole in the outer wall and insert an endoscope so that the cavity wall engineer can lay eyes on the actual cavity wall ties themselves. The Building Research Establishment (BRE) has laid out a detailed framework for assessing the condition of cavity wall ties based on their physical appearance.
This is reassuring because as the property owner it can be easy to feel helpful in such situations. However you need not feel at the mercy of cavity wall tie companies; the systems put in place for cavity wall surveys help to ensure that you get only the most accurate diagnosis and – if necessary – treatment.
After the initial assessment has been made your engineer will be able to discuss the various options available to you. In many cases it will be necessary to undergo cavity wall tie replacement, in order to remove corroded wall ties and instead swap them for the very latest wall ties that meet current quality assurance standards.