Concrete Driveway Repair: What Can Be Fixed and What Can't

Fine cracks that aren't moving, worn joints and small areas of flaking can all be repaired. A slab that has sunk, lifted or broken into pieces that rock underfoot can't, because the fault is in the ground beneath it, and anything you put in the crack will open up again. So the first job is working out which kind of damage you have, and the order below runs from most common to least.

1. Fine shrinkage cracks

These are thin, often wandering cracks, usually near a corner, a drain cover or the narrowest part of the drive. Concrete shrinks as it cures and dries, and if a joint isn't in the right place to take that shrinkage, the slab makes its own.

How to check: both sides of the crack are level, nothing moves when you stand across it, and it hasn't widened over a year.

The fix: clean the crack out, fill with a flexible concrete crack filler or sealant that suits the width, and reseal the surface. On imprinted concrete a filler can be tinted, but it won't vanish. The trade view is that rigid concrete can't be patch-repaired invisibly; the aim is to stop water getting in, not to make the crack disappear.

2. Joint problems

Plain concrete and pattern imprinted concrete driveways both have control joints (sawn lines) and expansion or isolation joints (a flexible strip where the slab meets a wall or another surface). Their sealant perishes, grit packs in and weeds take hold.

The fix: rake out, clean and re-seal with a flexible joint sealant. This is cheap, and it matters. Joints are where water gets under a slab.

If a drive has cracked in a straight line across its width every few metres and has no joints at all, the joints were never cut. Pavingexpert's rule of thumb is a joint roughly every 30 times the slab thickness, so about every 3m on a 100mm slab. The cracks have become the joints; seal them as joints.

3. Spalling and surface flaking

Spalling is when the top few millimetres flake or pop off, exposing the stone below. The usual causes are water freezing in the surface, de-icing salt, a surface that was overworked, finished with extra water or cured badly, and (on an imprinted drive) sealer that was allowed to wear away for years.

The fix: small areas can be cleaned back to sound concrete, roughened, patched with a polymer-modified repair mortar feathered to the surface and then sealed. Large spalled areas are a resurfacing or relaying question. On imprinted concrete a patch will show against the pattern, so many owners choose a restoration of the whole surface instead.

Prevention: keep the sealer up to date and go easy with rock salt, especially in the first winter.

4. Cracks with movement (structural)

Wide cracks, cracks where one side sits higher than the other, or a section that rocks when you drive over it are structural. The slab has lost support underneath.

The common causes are:

• A thin slab. LABC Warranty guidance gives 100mm as the minimum for a driveway slab, increased to 150mm on poor ground or clay. Thinner than that and normal car loads crack it.

• A poor sub-base. Too thin, not compacted, or laid on topsoil. The LABC minimum sub-base for a light-duty drive is 100mm of well-graded crushed stone.

• Soft ground. Old service trenches, a filled-in pond, tree roots removed, or clay that shrinks in dry summers.

• Water. A leaking drain or a downpipe discharging under the slab washes out the sub-base.

• Heavy loads. A skip, a lorry or a motorhome on a slab built for a car.

The fix: cut out the failed section back to sound concrete, sort the ground and sub-base underneath, and recast it. Filling a moving crack is a waste of money. On imprinted concrete the new section won't match exactly, so a neat repair often uses a contrasting band or border to frame the new area, which is the approach pavingexpert recommends after service work.

5. Sinking or lifting slabs

A whole bay that has dropped, or a lip where the drive meets the pavement or garage, means the ground has moved over a large area. If it's tipping water towards the house, it's urgent: LABC guidance is that drives should fall away from the building at no less than 1:80.

The fix: that bay comes out and is relaid on a rebuilt base, with drainage sorted if water caused it. If several bays are going, relaying the drive is usually cheaper over ten years than chasing sections.

What you can do yourself

These are fine for a careful homeowner:

• Filling fine, stable cracks with a suitable flexible filler.

• Raking out and resealing joints.

• Cleaning, killing moss and resealing the surface.

• Watching cracks: mark the ends in pencil with the date and check again in six months.

Do repairs in mild, dry weather. Cemex's guidance on concrete in the cold is that fresh concrete which falls below 0°C can freeze and be ruined, and most repair mortars and fillers have a minimum temperature on the tub.

When to call a contractor

Get a contractor out if the crack is wider than a coin's edge, stepped, growing, or the slab moves; if water ponds towards the house; or if a section has sunk. Those are base problems, and they need cutting out and rebuilding. At that point it's worth comparing the repair price against relaying the whole drive, which our concrete driveway cost post breaks down. A patio with the same symptoms is the same decision, and the concrete patio cost guide covers the patio side.

Concrete repair questions, answered

Are cracks in imprinted concrete normal?

Fine cracks along the sawn joints are expected; that's what the joints are for. Cracks across the pattern away from the joints usually point to a slab that was too thin, poorly based or not jointed. The trade line is that correct sub-base preparation and well-formed crack control joints should prevent unwanted cracking.

Can you repair a crack invisibly?

Not on concrete. You can make it neat, sealed and colour-matched as closely as possible, but a repair will always be visible up close.

Will my guarantee cover cracks?

That depends on what the guarantee says. Drive Tech's 10-year guarantee covers materials, workmanship and structure on the imprinted drives we lay, which is why we build them to full depth on a compacted base with mesh.

If your drive is past saving, we'll explain why on site rather than sell you a repair that won't last. For a look at the damage anywhere around Wolverhampton, Walsall or Cannock, contact us and Pete will come and look at it.