If you live in an older brick property in South Wales, Swansea, Bristol or Cardiff, wall tie corrosion might be something you have heard mentioned but not fully understood. Knowing what to look for and when to get help can prevent small defects from turning into expensive structural repairs.
What are wall ties, and what do they do?
Most brick houses built from the early 1900s onwards have cavity walls. This means there is an outer brick layer and an inner block or brick layer, with a gap between them for insulation and moisture control.
Wall ties are metal straps that sit in this cavity and link the inner and outer leaves together. They help the two layers act as a single, stable wall so your brickwork does not bulge or separate over time.
In older homes, these ties were usually mild steel with a galvanised coating to slow down rust. Over decades, that protection can fail, leaving the steel exposed to moisture, salts and air, which leads to corrosion.
How wall tie corrosion starts in older homes
Wall ties are hidden inside the cavity, so you never see them directly. Instead, they slowly deteriorate out of sight while the brickwork continues to look normal from the outside, especially in the early stages.
Several factors make older galvanised wall ties more likely to corrode:
Moisture in the cavity from rain penetration, porous bricks or leaking gutters
Mortar salts that react with metal and speed up corrosion
Age of galvanising, as old coatings were thinner and degrade over decades
Coastal exposure around Bristol Channel and South Wales, where salt-laden air is more aggressive
As the steel rusts, it expands. This expansion can push on the surrounding mortar and brickwork, eventually causing movement and cracking that becomes visible outside.
What does wall tie corrosion look like?
Because the ties are buried, you are looking for patterns in the brickwork rather than the metal itself. Not every crack means corroded ties, but there are some typical signs that raise suspicion.
Regular horizontal cracking in mortar joints
One of the most common indicators is thin, fairly straight cracks running along the mortar bed joints. These often appear:
At regular heights on the wall, sometimes following the line where the wall ties were placed during construction. The cracks can be more visible on exposed elevations or near corners.
Bowing or bulging brickwork
As ties corrode and lose strength, the outer leaf can start to move away from the inner leaf. You may notice sections of wall that look slightly bowed or uneven when viewed along the surface.
This can be subtle at first, especially on long walls or gable ends, and may be easier to spot in low sunlight where shadows highlight the distortion.
Stepped cracks and cracks around openings
Cracks that step along the mortar joints in a zig-zag pattern, often above or beside windows and doors, can suggest wall tie problems or other structural movement.
Gaps appearing at the corners of window or door frames, or bricks dropping slightly at the lintel ends, are also warning signs that the wall is not being held together properly.
Rust staining and spalled brick faces
In some cases, corrosion can lead to brownish rust stains bleeding through the mortar or brick faces. Bricks may also start to spall, where the front surface breaks away or flakes.
These symptoms alone are not proof of wall tie issues, but when combined with cracking and age of property, they strengthen the case for a professional survey.
Why guessing the cause of cracks is risky
Cracks in masonry can come from many sources, such as foundation movement, thermal expansion, roof spread or even minor settlement. Wall tie corrosion is just one possible cause.
Trying to diagnose the problem by eye, or simply filling cracks without investigating, can lead to the real issue continuing unchecked behind the scenes. This is particularly important where safety and structural stability are concerned.
A trained surveyor will assess the pattern, width and location of cracks, along with the building’s age, materials and exposure. They then use specialist tools to check the condition of the ties directly.
How a wall tie inspection or survey works
A proper wall tie survey is designed to confirm whether corrosion is present, how advanced it is, and whether it explains the visible problems. It also helps rule out other types of structural movement.
Typical steps in a wall tie inspection include:
External visual check of all elevations, noting cracks, bowing and previous repairs
Use of metal detectors to locate existing wall ties within the cavity
Small inspection holes drilled in mortar joints for a borescope camera or direct inspection
Recording tie condition across different wall areas to build a full picture
The survey findings are then set out in a clear report, usually with photos, explaining whether remedial work is needed and how urgent it is. This gives you a solid basis for any next steps, rather than guesswork.
Role of cavity wall insulation, debris and bridging
Many homes in Swansea, Cardiff, Bristol and across South Wales have had cavity wall insulation fitted over the years. In some properties this can influence moisture behaviour within the cavity.
If insulation is poorly installed, becomes saturated, or if debris and old mortar droppings bridge the gap between inner and outer leaves, moisture can linger around wall ties or track across the cavity. This can potentially speed up corrosion or lead to damp issues.
That said, not every home with cavity insulation will have wall tie problems, and not every corroded tie is caused by insulation. A good survey will look at the overall cavity condition, including insulation type, damp patterns and any bridging, before drawing conclusions.
When to call a wall tie specialist
If you notice regular horizontal cracking, bulging brickwork or stepped cracks around windows and doors, especially in a property built between roughly 1920 and 1980, it is sensible to seek specialist advice.
You should also consider a survey if you are buying or selling an older house in South Wales, Swansea, Bristol or Cardiff and the survey report flags potential wall tie concerns. Resolving questions early can avoid delays and renegotiations later.
Choose a contractor with specific experience in wall tie inspections and repairs, not just general building work, so you can be confident the correct diagnosis and treatment are recommended.
What happens after a wall tie survey?
The outcome of a wall tie survey will depend on how advanced the corrosion is, how many ties are affected, and whether the wall is already distorted. There are three broad paths that may be suggested.
Monitoring where movement is minor
If the survey shows only early-stage corrosion with no significant distortion, the recommendation may be to monitor rather than carry out immediate work. This can involve periodic visual checks and repeat measurements of any cracks.
This approach can be reassuring, as it confirms a professional is keeping an eye on the situation, rather than leaving you to wonder if things are getting worse.
Installing remedial wall ties
Where existing ties are corroding but the brickwork is still broadly in its original position, the common solution is to install remedial wall ties. These are usually stainless steel, designed to resist future corrosion.
New ties are fixed through the outer leaf into the inner leaf at set spacing, often using specialist resins or mechanical fixings. The fixing points are then patched to blend in with the surrounding mortar or brick colour as closely as possible.
Isolating or removing failed ties
Simply adding new ties is not enough if the old ones continue to expand as they rust. As part of a full remedial scheme, damaged ties are usually isolated or removed so they can no longer exert pressure on the brickwork.
Isolation methods vary, but the aim is always the same: stop the old metal from causing further cracking while the new stainless steel ties take over the structural role.
Making good and repointing
After remedial ties are installed and old ones dealt with, the final steps focus on appearance and weather protection. Cracks are raked out and repointed, and any disturbed areas are made good.
A careful contractor will take time to match mortar colour and joint style as closely as possible so the repairs blend in. This not only improves the look of your home but also helps keep moisture out of the brickwork.
Next steps if you are concerned about wall tie corrosion
Wall tie problems can sound worrying, but with a proper survey and a clear plan, they are usually manageable and can be resolved in a controlled way. The key is not to ignore warning signs or rely on guesswork.
If you own a property in South Wales, Swansea, Bristol or Cardiff and are seeing suspicious cracking or bulging in your brickwork, you can arrange a professional wall tie survey with Cavi Clear Ltd. Their team can assess the condition of your walls, explain the findings in plain language and advise on the most appropriate solution for your home.
To book a wall tie survey or discuss your concerns, contact Cavi Clear Ltd on 01639790426.
