Crack Repair: What Every UK Homeowner Should Know

Noticed a line popping up on your wall or floor? It might be more than a cosmetic issue. Cracks can signal movement, moisture, or even structural trouble. The good news? Most cracks are fixable if you act early and know what you’re dealing with.

How to Spot Serious Cracks

First, grab a ruler or a crack‑width gauge. Measure the width at three points – top, middle, bottom – and note the widest spot. In the UK, anything wider than 3 mm in a foundation slab or 1 mm in brickwork should raise a red flag. Look also at the pattern: a single straight line usually means shrinkage, while a stair‑step or jagged line often points to structural stress.

Next, check the orientation. Horizontal cracks on walls are more concerning than vertical ones because they can indicate pressure from soil or water. If the crack is growing – you can tape a piece of paper over it and mark the ends – you have a problem that needs professional attention.

Best Ways to Repair Different Cracks

For tiny hairline cracks (under 1 mm), a simple filler or flexible sealant does the trick. Clean the area, apply a polyurethane‑based product, and smooth it with a putty knife. This stops moisture from getting in and keeps the surface looking neat.

Wider cracks (1‑3 mm) in brick or blockwork need a bit more work. Use a masonry crack repair kit: chisel the crack to a V‑shape, clean out dust, then push in a cement‑based epoxy. The V‑shape gives the filler a good grip, and the epoxy expands slightly as it cures, sealing the gap tightly.

When you’re dealing with foundation cracks wider than 3 mm, it’s usually time to call a structural engineer. They’ll assess the cause – be it subsidence, settlement, or poor drainage – and recommend a repair method such as underpinning, grout injection, or installing a steel reinforcement plate. Trying a DIY fix on a heavy‑load foundation can do more harm than good.

If the crack appears in a concrete slab, clean it thoroughly, then use a hydraulic cement that sets quickly even under water. Press the mix deep into the crack with a trowel, and finish with a smooth layer to match the surrounding floor. For large slab cracks, a specialist may inject a polyurethane resin that expands and fills the void, restoring strength without heavy digging.

Don’t forget moisture management. Many cracks widen because water seeps into the ground and pushes against walls. Check your guttering, downspouts, and drainage around the property. Adding a French drain or improving soil grading can stop future movement.

Finally, keep a record. Photograph each crack, note the date, and track any changes over weeks or months. This documentation helps contractors understand the progression and can be useful for insurance claims if the issue worsens.

Crack repair might feel daunting, but with the right tools and a clear plan you can stop most problems before they get expensive. When in doubt, trust a qualified professional – it’s better to spend a little now than to face a costly structural failure later.