When Concrete Repair Is Not Enough, and What to Do Instead

What can surface repair realistically fix?

Surface repair fixes damage that lives in the top of a stable slab: hairline and shrinkage cracks, small potholes, spalling, broken joints and chipped edges, followed by a two-coat recolour. It restores the look and the integrity of the surface you walk and drive on.

What it cannot do is change what is happening under the slab. It does not lift sunken concrete, refill a washed-out base or stop ground movement.

Which signs mean the slab is moving?

The clearest sign is a height difference: one side of a crack or joint higher than the other, or a section of driveway that has visibly dropped. Others include slabs that rock when driven over, gaps opening between the slab and a wall, and cracks that grow from one season to the next.

• A step across a crack or a joint.
• Sunken areas where water now collects.
• Slabs that rock, tilt or sound hollow.
• Cracks that widen or lengthen over time.
• Similar cracks appearing in nearby walls or steps.
• A crack that reopens soon after being repaired.

What else makes surface repair the wrong answer?

A slab that is crumbling across most of its area is one case. Rebuilding nearly every square metre piece by piece costs effort without giving you a sound slab at the end.

Exposed or rusting steel is another. It means reinforcement inside the concrete is corroding, which is a matter for a qualified professional to assess, especially on slabs over garages, ramps or anything structural.

Finally, a hole that reaches soil or a void shows that the base has gone. Patching the top of it, as explained in our guide on potholes and spalling, does not restore the support underneath.

Who should you call when repair is not enough?

Start with a qualified engineer or surveyor who can investigate the cause. They can tell you whether the movement has stopped, what is causing it and what work is needed underneath.

If the answer is replacement, a builder carries out the demolition and new slab. We do not do structural surveys, foundation work, demolition or new concrete, so we have nothing to sell you in that scenario except honest advice.

If the engineer confirms the slab is stable or the cause has been dealt with, surface repair becomes an option again. Then our crack repair, pothole repair and imprinted concrete repair services apply.

Do you need permission for repair or replacement in Andalusia?

Andalusia's planning law, Ley 7/2021 (LISTA), sets out which works need a licence (art. 137) and which can be done with a declaración responsable (art. 138); according to a municipal model form, art. 138.1.a covers minor, technically simple works that need no project. Its general regulation is Decreto 550/2022.

In Málaga city, the planning department's list of works treats minor works that need no project as a declaración responsable in general, while some areas, such as protected settings, need a licence. The city's fee ordinance lists the repair or coating of exterior slabs in gardens, pool areas and common areas as a minor work.

For Marbella, Estepona, Mijas, Fuengirola, Benalmádena and Torremolinos, the procedure has not been verified (to be verified). Depending on the municipality and the area, a declaración responsable or a licence may be needed, so confirm with your ayuntamiento before any work starts, especially for replacement.

What happens to the rubble if a slab is replaced?

Breaking out concrete produces construction and demolition waste, which in Spain is regulated by Real Decreto 105/2008 on the production and management of that waste. Whoever does the replacement should explain how the rubble will be handled.

This is one of the practical differences between the two routes. Repair leaves the slab in place, so there is no demolition rubble to deal with.

What if the damaged concrete belongs to a community?

If the slab is a common element, such as a shared driveway or the ramp to a community garage, decisions go through the community. Under the Ley de Propiedad Horizontal, art. 10.1, works necessary for proper upkeep and the duty of conservation are compulsory and do not need prior agreement of the owners' meeting, which only decides how the cost is shared.

Improvements that are not required need a qualified majority under art. 17. The administrator is the right person to say which category your works fall into.

How do we handle borderline cases?

When photos show something that might be movement, we say so and suggest an engineer before we quote. We would rather lose a job than paint over a problem that will come back.

Our article on red flags before repairing concrete gives you a quick checklist, and the guide on crack types explains the signs in more depth.