Wall tie condition survey
An inspection of the metal ties that hold the two leaves of a cavity wall together, which can corrode and cause cracking or bulging.
About this service
A wall tie condition survey checks the metal ties that hold the inner and outer leaves of a cavity wall together. When ties corrode, the rust expands and lifts the mortar beds, creating horizontal cracks and, in time, bulging brickwork. In the worst cases the outer leaf loses its connection to the structure behind and can become unstable in high winds.
In London the problem is mostly found in houses from the interwar period onwards, because most Victorian and Edwardian homes have solid walls without ties. Early ties were often galvanised steel with thin protection, and in some areas black ash mortar made corrosion faster. The classic sign is a horizontal crack in the mortar repeating every few courses, matching the spacing at which ties were built in.
We inspect the brickwork, use an endoscope to look at ties through small holes in the mortar where accessible, identify the tie type and judge its condition. The report sets out whether replacement is needed and how extensive it should be. It is signed off by a chartered engineer (MICE). Surveys start from £250 + VAT, which is modest compared with replacing ties that are actually sound.
When you need it
- You see horizontal cracks in mortar joints at regular intervals
- Walls appear to bulge or lean
- A survey has flagged possible wall tie failure
What's included
- External inspection of the brickwork
- Endoscope checks of ties where accessible
- Assessment of tie type and condition
- Replacement recommendations
How it works
- Initial detailsWe ask about the property's age, the cracking you have seen and any survey that raised concerns, then confirm the fee and visit time in writing.
- External inspectionThe engineer examines each elevation for horizontal cracking, bulging, lifting at roof level and other signs of tie corrosion, as well as alternative causes of cracking.
- Endoscope checksSmall holes are drilled in mortar joints at selected points so an endoscope can view ties in the cavity, revealing their type and degree of corrosion.
- Report and recommendationsYou receive a wall tie condition report explaining what was found, whether replacement is needed, which elevations are affected and what a sound repair specification should include.
What you receive
Is it really wall tie failure? Ruling out other causes
Horizontal cracking is not always caused by ties. Thermal and moisture movement, sulphate attack in mortar, roof spread pushing walls outwards, and failed lintels can all produce cracks that look similar to an untrained eye. Replacing ties will not fix any of these. That is why our inspection looks at the whole wall, not just the ties, and why the endoscope checks are important. Our guide on signs of wall tie failure explains the patterns we look for.
Some homeowners are told they need full tie replacement on the strength of one crack. A proper survey may show the problem is limited to one elevation or level, or that ties are corroded but not yet failing. If replacement is recommended, the work should include new remedial ties fixed into sound masonry and, in many cases, isolation or removal of the old ties. Bulging walls may need further work, which can be covered by remedial works design.
Frequently asked questions
What are the signs of wall tie failure?
The most common sign is horizontal cracking in mortar joints repeated at regular intervals up the wall, typically every few courses. Others include bulging or leaning outer brickwork, cracking at window heads, and the roof edge lifting slightly where the wall has expanded. These signs develop slowly, often over many years, and should be checked by an engineer.
How do you check wall ties without damaging the wall?
We drill small holes in mortar joints, not bricks, and insert an endoscope to see the ties in the cavity. The holes are tiny and easily filled afterwards. A metal detector may also be used to locate tie positions. This allows us to assess tie type and corrosion without taking down any brickwork.
Do Victorian houses have wall ties?
Most do not. The majority of Victorian and Edwardian houses in London have solid brick walls, bonded together with headers rather than ties. Cavity walls with ties became common in the interwar period. Some later extensions to older houses do use cavity construction, so it is worth checking how each part was built.
Is wall tie replacement covered by home insurance?
Usually not. Wall tie corrosion is generally treated as gradual deterioration rather than a sudden event, and most policies exclude it. It is worth checking your own policy wording. An engineer's report helps you understand the extent of the work needed before you obtain quotes from specialist contractors.