Cavity wall tie failure is one of the most common structural issues affecting UK homes, yet most homeowners don’t realise there’s a problem until cracks begin to appear. If you’re seeing horizontal cracking in brickwork or subtle bulging to an external wall, corroded wall ties could be the underlying cause. At CavClear, we carry out specialist cavity wall tie surveys nationwide. Here’s what you need to know.
What Are Cavity Wall Ties?
Cavity wall ties are metal connectors built into the cavity between the outer brickwork and the inner blockwork of a property. Their purpose is to hold the two leaves together while still allowing the cavity to perform its job of preventing moisture transfer.
They are small components, but structurally critical. Without them, the outer brick leaf has no restraint against wind load or movement. Most properties built between the 1920s and early 1980s were constructed using mild steel wall ties and that’s where the problem often begins.
The Main Cause of Wall Tie Failure: Corrosion
The primary reason cavity wall ties fail in the UK is corrosion. When mild steel is exposed to moisture inside a cavity, it begins to rust. As steel corrodes, it expands significantly creating internal pressure within the mortar bed joints where the ties sit.
Over time, this expansion forces the surrounding brickwork apart. The result is typically horizontal cracking along mortar lines, often appearing at regular intervals that match the spacing of the wall ties. This isn’t cosmetic cracking. It’s structural movement caused by expanding metal within the wall.
Why Do Wall Ties Corrode?
Moisture is the trigger, but several factors contribute to accelerated corrosion. In older properties, protective galvanisation on wall ties was often thin or inconsistent. Once that coating breaks down, corrosion can progress rapidly.
Environmental exposure also plays a role. Homes in coastal areas or high rainfall regions are more vulnerable due to increased moisture penetration. In some cases, retrofitted cavity wall insulation can worsen the issue if it becomes saturated. Wet insulation can hold moisture against the wall ties, significantly accelerating corrosion. This is why wall tie failure and cavity wall insulation defects are sometimes discovered together. Age alone is another factor. Many properties are now reaching the stage where original ties have simply exceeded their lifespan.
How to Spot Failing Cavity Wall Ties
The most recognisable sign is horizontal cracking in the mortar joints, typically running straight across the brickwork. You may also notice slight bulging or bowing of the external wall. In more advanced cases, cracking can appear around window and door openings, or the brickwork may begin to separate slightly from the frame. The pattern is usually consistent and evenly spaced, a strong indicator that the issue lies within the wall rather than with foundations or lintels.
What Happens If It’s Left Untreated?
Wall tie corrosion does not stabilise on its own. As rust continues to expand, cracking worsens and structural stability can be compromised.
In severe cases, the outer brick leaf can lose adequate restraint. While this is rare, it is why early diagnosis is important.
Beyond structural concerns, wall tie failure can also affect mortgage approvals and homebuyer surveys, particularly if cracking is visible.
The earlier the issue is identified, the more straightforward and cost-effective the solution tends to be.
How Is Wall Tie Failure Resolved?
The modern solution is the installation of new stainless steel remedial wall ties. Specialist ties are inserted through the mortar bed joints and mechanically fixed to both leaves of the wall. The original corroded ties are isolated to prevent further expansion, and affected mortar joints are made good. Stainless steel ties are highly resistant to corrosion, providing a long-term structural fix.
Professional Cavity Wall Tie Surveys Nationwide
Accurate diagnosis is essential. Not all horizontal cracking is caused by wall tie failure, and misdiagnosis can lead to unnecessary work.CavClear provides specialist cavity wall tie surveys across the UK, using non-invasive inspection methods and detailed reporting to clearly identify whether corrosion is present and to what extent. If you’ve noticed cracking brickwork, bulging walls, or concerns raised in a homebuyer survey, arranging a professional inspection is the first step.
Concerned About Cracking Brickwork?
Cavity wall tie failure is common, but when identified early, it is entirely manageable. If you suspect corroded wall ties, contact CavClear today to arrange a professional cavity wall tie survey. Call 0333 220 2463 or enquire online to book your inspection.
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