Wall Tie Replacement in Liverpool

What are wall ties and why do they fail?

A cavity wall is two thin walls, or leaves, with a gap between. Metal ties built into the mortar joints of both leaves hold them together, so they work as one wall against wind and loads. In much 20th-century construction, and some earlier cavity work, those ties were mild steel, sometimes galvanised. LABC Warranty’s guidance on wall tie replacement in existing buildings describes common types such as vertical twist, fishtail and butterfly wire ties. Over decades, moisture in the outer leaf corrodes them.

Corrosion fails in two ways. Thick flat ties, such as vertical twist, can rust and expand within the mortar of the outer leaf, lifting the brickwork and opening horizontal cracks. Thin wire ties, such as butterfly ties, tend to corrode away quietly, leaving the outer leaf unrestrained with almost no visible warning. Coastal exposure, porous bricks, poor-quality original zinc coatings and defective pointing can all speed up the process.

What are the signs of wall tie failure?

• Horizontal cracks in the bed joints, repeating at regular vertical intervals. LABC notes ties are typically at 450 mm vertical centres, so cracks roughly every six courses of brickwork are a classic pattern.
• A bulging or bowing outer leaf, particularly on gable walls and at high level where the wall is least restrained.
• Cracking around window and door openings and at the corners of the house.
• Lifting at the roof line or verge, as expanding ties push up the outer brickwork.
• No signs at all, in the case of corroded wire ties. An inspection with a borescope through a drilled joint is the only way to know.

Horizontal cracking can have other causes, such as sulphate attack on mortar or expansion of the brickwork, which is one reason an inspection matters before deciding on tie replacement. Where cracks are diagonal or tapering, foundation movement may be involved instead, and our structural crack repair page explains how those are approached.

How is a wall tie problem confirmed?

The engineer or specialist inspects the crack pattern and the condition of the brickwork, then uses a metal detector to locate existing ties and a borescope through small holes drilled in the mortar to see the ties inside the cavity. Sometimes a few bricks are removed to expose ties in the outer leaf, so their thickness and corrosion can be judged. This identifies the tie type, its spacing and how badly it has corroded, which shapes the remedial specification.

How is wall tie replacement carried out?

1. Specification. The engineer sets out the remedial tie type, the pattern and density, and how the old ties are to be dealt with. LABC Warranty cites around 2.5 remedial ties per square metre, staggered away from the old tie positions, as a typical arrangement.
2. Access. Scaffolding or other safe access is arranged for the full height of the affected walls.
3. New ties fitted. Stainless steel remedial ties are installed through the outer leaf into the inner leaf, fixed mechanically or with resin depending on the specification and the masonry.
4. Old ties dealt with. Where old ties are expanding and cracking the brickwork, they may need to be isolated or removed from the outer leaf. Where thin ties have simply corroded away, isolation may not be needed. BRE Digest 329 covers how this is decided.
5. Making good. Drill holes and opened joints are repointed to match, and cracked or displaced brickwork is repaired or, if badly lifted, rebuilt.
6. Sign-off. The work is inspected against the specification by the engineer, and by Building Control where it applies.

Is wall tie replacement the same as fixing a bowing wall?

They overlap but are not the same. Replacing ties reconnects the two leaves; it does not by itself restrain a wall that has lost its connection to floors or roof, and it will not straighten a wall that has already bulged significantly. Where an outer leaf has moved too far, the engineer may specify rebuilding that section with new ties. Our bowing wall repair page covers restraint and rebuilding, and badly corroded steel lintels, which often fail alongside old ties, are dealt with through lintel replacement.

Which Liverpool homes are likely to need new wall ties?

Cavity walls became common in the inter-war years, so inter-war and earlier post-war houses are the main age range where original mild steel ties have reached, or are reaching, the end of their life. Homes on exposed coastal fronts, such as parts of Crosby, Wallasey and Southport, see more wind-driven rain, which can accelerate corrosion. Many Victorian houses have solid walls without cavity ties at all, though some later Victorian and Edwardian houses do have early cavity construction. We carry out remedial tie work across Merseyside alongside our underpinning and subsidence repairs in Liverpool.

What affects the cost of wall tie replacement?

The area of wall to be treated, the number of elevations, and the height of the building set the baseline. Scaffolding is often a significant part of the cost. After that: the tie type and density specified, whether old ties must be isolated or removed (which is far more labour-intensive than simply fitting new ones), the extent of cracked or lifted brickwork to rebuild, repointing to match, and any related work to lintels or restraint. We quote against the engineer’s specification once the inspection has shown what is needed.