Cavity Wall Tie Replacement
Cavity walls have been constructed since the beginning of the 20th century and were implemented to offer better protection from the elements as well as reduce the amount of unnecessary heat loss from the property. The system comprises of two separate walls, the internal and external walls which are ‘tied’ at strategic intervals using a form of wall tie commonly made of metal coated in bitumen or zinc, known as cavity wall ties.
If your property is suffering from wall tie failure then this can mean that both skins (or leaves) become independent of each other. This means that the property can become structurally unsafe and a danger to those that may be in it or around it.
What is Wall Tie Replacement?
Wall tie replacement is the replacing of corroded or otherwise damaged wall ties that hold together the internal and external walls with replacement wall ties that are designed to be retrofitted into existing walls. Corrosion of wall ties is particularly common in coastal areas as a result of the high salt content.
Identifying Cavity Wall Tie Failure
There are a number of clear signs to look out for to see if your properties wall ties are affected:
• Horizontal Cracks – in a mortar, often at a high level, caused by the expansion of corroded wall ties.
• Bulging walls/brickwork – caused by snapped wall ties, which have corroded. This can make your property unstable.
• Bowing walls
• Lintels sagging
• Cracks or separation of the window reveals
Carrying Out a Wall Tie Survey
A wall tie survey is usually straight forward and takes around an hour or so to conduct. With the survey relying heavily on the inspection of the outside of the property these surveys have to be carried out in daylight hours. When the surveyor arrives at the property they will initially inspect the exterior of the property. In particular, they will look at the following:
• The construction of the property
• Any cracks or bulges that are visible
• Check for the presence of a cavity wall and if so if there is any insulation within the cavity
Following on from this the surveyor will then locate the exact positions of the ties by using a metal detector. This may involve the use of a ladder depending on any areas of concern identified with the initial external inspection. Once the location of a selection of wall ties has been identified the surveyor will drill an inspection hole.
To check the condition of the wall ties within the wall a borescope is used. A borescope can be viewed as the endoscope of the construction world. Where there is no insulation present in the cavity the surveyor will have a very good view of the wall ties as the borescope illuminates the wall ties.
The condition of the wall ties can then be graded in line with digest 401 published by the Building Research Establishment. This document explains how to grade the condition of the wall ties as well as recommending actions that need to be taken. There are nine classes of wall tie ranging from 1 where the wall tie is showing no signs of corrosion and shiny through to 9 where there is visible corrosion to the ties.
Other factors are also taken into consideration by the surveyor such as the type of wall tie, the number of wall ties used, the presence of cavity wall insulation and the general exposure of the building to the elements.
In cases where there is cavity wall insulation present, a borescope surveyor may not be possible and a more invasive method of checking the condition of the wall ties may be required.
Why we are trusted to do the job
Timberwise have fully trained and experienced surveyors who have a range of solutions at their disposal to solve your cavity wall tie problem. Our surveyor will recommend the most suitable structural repairs for your property as well as providing a written report for the work to be carried out.
Need a Cavity Wall Tie Replacement in your property
If a problem with cavity wall tie corrosion has been identified, our specialist technicians who will provide the right treatment to your corroded wall ties. Contact Timberwise via our let’s chat button by calling on 0800 288 8660 or you can request a survey online.