What are the signs of cavity wall tie failure?
Visual evidence can be seen by horizontal cracking through the brickwork and mortar of external wall surfaces or hairline cracking to external render. In its advanced stage, the corrosion of the wall ties will expand causing horizontal cracking in the brickwork and eventually loss of stability between the two skins of brickwork. If corrosion is severe or neglected this may lead to bulging of the wall.
It’s not just older properties are affected by the failure of cavity wall tie systems. New build properties are also being found to require supplementary wall tie systems where insufficient ties have been implemented or omitted altogether in the build process.
Wall Tie Surveys
Our structural remedial surveyors use a combination of visual impression and investigatory procedures when carrying out a wall tie survey. A visual inspection will be carried out in the first instance and if further investigation is needed to assess the condition of the wall ties within the cavity wall, then we will carry out an intrusive wall tie survey. This will involve the use of a metal detector to locate the wall ties and via a small hole drilled into the wall, inspection of the condition of the wall ties inside the cavity using a borescope camera.
During the wall tie survey, our structural remedial surveyor will be assessing for the grade of corrosion to determine if and what actions need to be taken. A thermal imaging camera can also be used to indicate signs of moisture which may be impacting the corrosion to the wall tie.
Installation of Wall Ties
A combination of works is usually required in order to install a full wall tie system correctly. Remediation works can involve isolating the failed ties and installing high grade ties made from a non-corrosive material meaning the wall will be left stable and secure for many years to come.
The wall tie installation itself is completed by drilling through the outer wall and into the inner wall usually from the outside of the building. Once the wall ties are installed, random ‘pull out’ testing is carried out to ensure the correct fixing strength has been achieved.
Wall tie replacement is a technical process and accordingly we use only our own trained and experienced in-house structural repair surveyors and operatives to survey and carry out this work. It is important to note that a structural survey carried out by a qualified Structural Engineer may be necessary in the first instance. We will advise if this is the case.
Other Types of Structural Repairs
In addition to wall tie replacement, other structural repairs may also be necessary to form part of a full long lasting repair system. Such structural repairs include crack stitching, installation of lateral restraints and carrying out a concrete repair to corroded and spalling concrete such as window cills.
Re-pointing of brickwork or masonry protection applications such as Stormdry may also be necessary to stop and reduce the amount of moisture that can penetrate through the wall. This is particularly common where soft porous bricks are present.