Wall tie replacement for cavity walls
Cavity walls are two leaves of masonry held together by metal ties. In older cavity walls, those ties can corrode and fail, letting the outer leaf crack, bulge or lose support. Wall tie replacement fits new remedial ties and deals with the old ones before the damage spreads. ADB SW’s masonry and structural work covers South Devon. Send photographs of any horizontal cracking and the age of the house if known.
Why wall ties fail
Many houses built with cavity walls through the twentieth century used steel ties with a protective coating that was thinner than later standards require. Over decades, moisture in the outer leaf corrodes them. Wire ties gradually thin until they lose their strength, while thicker strip ties can expand as they rust and push the mortar joints apart.
Exposure speeds this up. Walls facing prevailing wind and rain, and houses close to the sea where salt is carried in the air, tend to see corrosion earlier. Black ash mortars, used in some areas, can also be more aggressive towards ties. Age alone is not proof of failure, but it is a reason to look.
Signs of wall tie failure
The most typical sign is horizontal cracking in the mortar joints, repeating at regular vertical intervals that match the tie spacing. Expanding ties can make the outer leaf rise slightly, lifting the roof edge or opening cracks at window heads. Bulging walls, cracked render along regular lines and gaps at the eaves can all point the same way.
Not every horizontal crack means failed ties. Thermal movement, sulphate attack and other defects can look similar. A proper assessment uses a borescope or opens up sample points to see the condition of the ties inside the cavity and identify the type and spacing before any remedial design is agreed.
How wall tie replacement works
Remedial ties are installed from outside by drilling through the outer leaf into the inner leaf and fixing a stainless steel tie that grips both. Mechanical, resin and helical tie systems are available, and the right choice depends on the masonry and the cavity width. Ties are fitted to a pattern that meets current guidance, with extra ties around openings and at edges.
The old ties also need attention. Where they are expanding, they are usually removed or isolated so they cannot continue to crack the outer leaf. Holes are then filled with matching mortar and any cracked joints repointed, so the finished wall looks tidy. Where the outer leaf has bulged or moved significantly, sections may need taking down and rebuilding.
Arranging an assessment and quote
Cost depends on the wall area, height and access, the type of masonry, the number of old ties that need removing rather than isolating, and any rebuilding or repointing afterwards. Rendered walls may need render repairs once the ties have been installed. Scaffolding is often required for upper floors and gable walls.
For an enquiry, send photographs of the cracking, the elevations affected and any survey report that mentions wall ties. ADB SW can discuss the scope and provide a written quote. Where significant movement is involved, a structural engineer’s input may be recommended before the remedial work is specified.
Common questions
What are the signs of wall tie failure?
Horizontal cracks in mortar joints at regular vertical intervals, bulging brickwork, cracks at window heads, lifting at the eaves and cracked render running in straight lines.
How long does wall tie replacement take?
It depends on the wall area, access and whether old ties need removing. Many houses take days rather than weeks, but scaffolding and rebuilding add time.
Do old wall ties have to be removed?
Expanding ties that are cracking the masonry are usually removed or isolated. Thin wire ties that have simply lost strength may be left in place once new ties are fitted.
What affects the cost of wall tie replacement?
Wall area, height and access, masonry type, the number of ties to remove or isolate, and any repointing, render repairs or rebuilding needed afterwards.
Tell us about your project
Send the property details and the work you have in mind so the scope can be discussed before a quote is agreed.