Cavity Wall Ties
1. Wall Tie Survey
A wall tie survey aims to establish the condition of the wall ties within your external cavity walls. Wall ties are so-called because they “tie” the inner and outer leafs of your cavity walls together. As wall ties age, they eventually rust and corrode, leading to failure. This results in the cracking and deformation of your walls, and can lead to collapse of walls if the problem is not rectified.
Using the latest in optical boroscopes and metal detection technology, our operatives can find, survey and replace wall ties which are in poor condition or corroding; along with wall ties that have already failed. This technology allows the Surveys carried out to be non-destructive as the survey only requires small holes (diameter of a pen) to be drilled in the outside mortar joints in order for our boroscope to be inserted into the cavity.
A Wall Tie Survey will ascertain the condition of the existing wall ties, if and where the wall ties need replacing, along with deducing the best and most cost effective method of wall tie replacement for your house.
2. What is a Wall Tie?
External walls are normally constructed of 2 x 112mm walls built 50mm apart. To stop these walls collapsing a wall tie is placed across the cavity to tie both leafs together. A wall tie is normally made of metal which is coated with zinc or bitumen.
3. What is wall tie failure?
Wall tie failure is the corrosion of the protective coating of the wall tie, and not as most people assume the actual breaking of the tie.
4. Why replace the wall ties?
The metal wall ties rust over a period of time, this rusting will cause the tie to expand up to 7 times the original thickness, assuming a tie is approximately 4mm when new it could expand up to 28mm.
The pressure caused by the ties expanding causes horizontal cracking, bulging of the damaged walls and in extreme cases the collapse of damaged walls.
It is therefore essential to identify the type of existing cavity wall ties present, in order for the correct treatment to be undertaken, as either isolation of the existing corroding wall ties from the outer leaf embedment may be required or complete removal of the existing corroded wall ties may be required.
5. Do the existing wall ties need to be removed?
Not necessarily, thin metal wall ties such as twisted wire ties (Butterfly Ties) do not have a sufficient thickness of metal to cause horizontal cracking of the mortar bed joints due to the expansion as a result of the corrosion process, as such these wall ties, and many other types can be left in place, along with the installation of the new Stainless Steel cavity wall tie system.