Structural Crack Repair in Liverpool

How do you tell a structural crack from a cosmetic one?

Most houses have some cracks. Hairline cracks in new plaster, shrinkage cracks where ceilings meet walls and fine lines along plasterboard joints are common and usually harmless. The BRE's damage categories, set out in Digest 251, grade cracks from 0 to 5. Categories 0 to 2, with crack widths up to about 5 mm, are described as aesthetic and usually need only redecoration. Categories 3 and 4 affect serviceability, such as weather-tightness and doors or windows that stick. Category 5 is about stability and is likely to need structural intervention.

Width is only part of the picture. These features often point towards a problem worth investigating:

• A crack that is new, or that is visibly getting wider over weeks or months.
• Cracking that shows on both the inside and outside face of the same wall.
• A crack that is wider at the top than the bottom, or one that runs down through the damp-proof course.
• Stepped cracks around bays, corners, or at the junction with an extension.
• Horizontal cracks in mortar joints at regular heights, which can be a sign of corroding wall ties.
• Bulging or leaning brickwork, or brickwork sagging over an opening.

Photograph and date any crack you are worried about, with a ruler alongside. That record is useful to an engineer, an insurer and us. The subsidence and cracks guide goes into more detail on reading crack patterns.

What causes structural cracking in Merseyside homes?

We see a recurring set of causes on underpinning and structural repair jobs across Liverpool, and each one needs a different fix:

• Foundation movementSubsidence from clay shrinkage or leaking drains, heave from swelling clay, or a footing that is simply too shallow. The cause has to be dealt with before cracks are repaired.
• Failed lintelsCorroded steel, rotten timber or missing lintels over bays and openings lead to cracking and sagging above windows and doors. See lintel replacement.
• Corroded wall tiesOlder mild steel ties rust and expand, cracking bed joints and pushing the outer leaf out. See wall tie replacement.
• Lack of restraintGable walls and long flank walls not properly tied to floors and roof can bow and crack.
• Junction movementExtensions and bays built on different foundations from the main house move differently, opening a crack at the joint.
• Thermal and moisture movementLong runs of masonry without movement joints can crack as they expand and shrink. This is often not a foundation problem at all.

What does the repair process look like?

1. Initial call and visit. We ask where the cracks are, how wide, whether they are new or growing, and about trees, drains, extensions and any insurer or buyer involvement, then visit to look.
2. Engineer's assessment. Where the cause is not obvious, a structural engineer's survey comes first. The engineer may ask for crack monitoring, trial pits or a drain survey.
3. Cause dealt with. A drain repaired, a lintel replaced, wall ties renewed or, where the engineer specifies it, the foundation strengthened.
4. Crack repair. Typically raking out and stitching the crack with helical bars, replacing broken bricks, rebuilding badly damaged sections and repointing to match.
5. Making good. Internal plaster cracks repaired once the structure is sound, and the wall left ready for decoration.

Do cracks after subsidence need underpinning?

Usually not. The RICS consumer guide says fewer than 5% of properties affected by subsidence require underpinning. Once the cause is removed and monitoring shows the house has stopped moving, the cracks themselves can be repaired. Underpinning is considered when the cause cannot be removed or the footing is too shallow for the ground, and the decision is the engineer's (and, on an insurance claim, the insurer's). If it is needed, we explain the options, from mass concrete underpinning to piled solutions, in plain English.

Where in Merseyside do these repairs come up?

Crack repair work follows older housing. Bays and long terraced elevations in places like Wavertree and Walton often show cracks around openings and at shared walls, while larger Victorian and Edwardian villas in Birkenhead, including Oxton and Claughton, bring tall gables and big window openings. Whatever the property, the approach is the same: find the cause, then repair to the engineer's design.

What affects the cost of structural crack repair?

Price depends on how many cracks there are and how long, the wall thickness and brick type, access and scaffolding, whether lintels or wall ties are involved, any investigation or monitoring, Building Control involvement and internal making-good. We quote in writing once the engineer's specification is settled, rather than putting a figure on an unknown cause.