Concrete Repair near you

Patching earns its keep where the defect is local and the cause has stopped. A single spalled corner on an otherwise sound step, damage from an impact, a hole left by a removed fixing, or a small area of surface breakdown at a door threshold are all good candidates, provided the surrounding concrete rings solid when it is tapped and the steel, if any is exposed, is treated before the mortar goes on.

Patching is the wrong answer where the deterioration is widespread or still active. If tapping the surface finds hollow areas well beyond the visible damage, if several separate craters have opened along the same line, or if the concrete is saturated because water keeps arriving from a failed gutter, a blocked gully or a raised garden, then patch repairs will simply move the failure a few centimetres outwards each time. The same is true of a slab that has broken because the ground under it has moved: rebuilding the top of it leaves the cause entirely untouched.

The most useful thing you can ask a contractor is what they think the mechanism is, what evidence supports that, and what they expect to happen to the concrete next to their repair. Someone who has sounded the surface, looked for the water, and can say where they intend to cut back to is giving a different kind of answer from someone who has quoted a number of square metres of filler.

Reinforced autoclaved aerated concrete, usually shortened to RAAC, is described by HSE as a lightweight form of precast concrete commonly used in buildings in the United Kingdom between the mid-1960s and the mid-1980s, mainly in roofs and occasionally in floors and walls. HSE states plainly that it is less durable than traditional concrete and that there have been problems as a result which could have significant safety consequences, namely that it is liable to collapse.

This matters to homeowners because RAAC turns up in housing as well as in schools and public buildings, particularly in flat-roofed properties of that period. It looks different from ordinary concrete: pale, with a bubbly, aerated texture rather than visible stones, and soft enough that a screw or nail can be pressed into the surface. Panels may bow or sag, and from below you may see a gap opening between two adjacent panels.

The response is not a contractor with a bag of repair mortar. HSE's guidance to anyone responsible for the management, maintenance or alteration of buildings is to establish whether the building contains RAAC and then take steps to manage and control the risk, and it points to a competent structural engineer to assess it and develop a management plan. If a surveyor, a builder or a neighbour raises RAAC in a property of that age, treat it as a structural engineering question and stop anybody drilling, loading or cutting into the panels in the meantime.

Cement is the part of a concrete repair that injures people, and the injuries are worse than most homeowners imagine. HSE states that a serious burn or ulcer can rapidly develop if wet cement is trapped against the skin, and that in extreme cases these burns may need a skin graft or cause a limb to be amputated. The classic domestic version is kneeling in fresh concrete in ordinary trousers, or a boot filling with wet mix and being left on for the rest of the afternoon, because cement burns are not immediately painful the way a heat burn is.

There are two slower effects as well. HSE says cement can abrade the skin and cause irritant contact dermatitis, and that cement also contains hexavalent chromium, or chromate, which can cause allergic contact dermatitis through sensitisation. It notes that manufacturers add an ingredient to reduce that risk but that the addition is only effective for a limited period, after which chromium levels may increase again. That is why bagged cement carries a shelf life and why old stock in the back of a garage is not the bargain it appears to be.

None of this makes a repair a job to avoid, but it does set the standard you should see on site. Waterproof gloves and covered arms and legs, knee protection that does not soak through, boots that are tucked into rather than filled by the mix, and washing water available on site rather than at the end of the day. A crew mixing repair mortar barehanded in your garage is telling you something about how the rest of the job will be run.

The first stage is defining the repair area, which is almost always larger than the visible damage. The surface is tapped to find the hollow, debonded concrete around the crater, and the edges of the repair are cut to a square shoulder rather than feathered, because a feathered edge has no thickness at its perimeter and breaks away. Cutting is where the dust risk sits, and it should be done with water suppression or on-tool extraction rather than dry.

Then the steel is dealt with. Corroded reinforcement is exposed all the way around, back to sound bright metal beyond the corrosion, cleaned, and treated or replaced as the specification requires. Leaving the back face of a bar buried in chloride-contaminated concrete is the classic reason a repair fails: the corrosion simply continues behind the new mortar and pushes it off in turn. Where the steel has lost significant section, that is an engineering question rather than a mortar question.

Finally the repair is rebuilt and cured. A bonding treatment or primer is used if the mortar requires it, the repair material is placed in the thicknesses it is designed for rather than in one deep dollop, it is finished to match the surrounding surface, and it is protected while it gains strength. Ask what the curing arrangement is, particularly outdoors between autumn and spring, because a repair left to freeze in the first few days will not reach the strength it was bought for.

The variables here are diagnosis, access and depth rather than area. A quotation moves according to how much sound concrete has to be cut away to reach a solid edge, whether reinforcement is involved and in what condition, whether the repair is at ground level or on a step, a balcony or a wall where working platforms are needed, how much breaking out and cutting is required and how the dust and debris will be controlled, what repair material the specification calls for, and whether the water that caused the damage is being fixed as part of the same job or left for later. A structural engineer's involvement, where the defect turns out to be structural, is a separate and worthwhile cost.

LokalMatch exists to get you those quotations side by side. Post the job once with your postcode, photographs of the damage and what you know about its history, and concrete and building contractors who cover your area will contact you directly. It costs a homeowner nothing to ask, since the professionals pay for the requests they receive. LokalMatch does not carry out repairs, does not set prices and does not vet, rank or recommend anyone who gets in touch, so satisfying yourself about their diagnosis, their insurance and their method statement remains your responsibility.