Concrete Repair near you

Queensland's Standards and Tolerances Guide gives homeowners a way to answer that without an argument. For concrete floors it reproduces a damage classification drawn from AS 2870, which combines crack width with the change in offset measured from a 3 m straight edge placed over the defect. Hairline cracks under 0.3 mm with an offset under 8 mm are negligible; fine but noticeable cracks under 1.0 mm with an offset under 10 mm are very slight; distinct cracks under 2.0 mm with an offset under 15 mm are slight; wide cracks of 2 mm to 4 mm with 15 mm to 25 mm of offset are moderate; and gaps of 4 mm to 10 mm with more than 25 mm of offset are severe.

The guide then states which of those are defects: Category 3 and 4 cracks to slabs are defects, and Categories 1 and 2 are not. It also notes that local deviation of slope from the horizontal or vertical of more than 1:100 will normally be clearly visible, and that overall deviations in excess of 1:150 are undesirable, and that the past history of damage should be taken into account in judging whether it is stable or likely to increase.

Two other clauses are worth knowing before you commission a repair. The guide says repairs to exposed concrete slabs are defective within twelve months if they do not, as closely as practicable, match the existing work in appearance, colour and texture, while accepting that minor variations in finish are not defective. And where the slab is part of a termite management system, any repair is defective unless on completion the termite management system is appropriately reinstated in accordance with the NCC.

It starts with a survey rather than a patch. The whole element is sounded — tapped or chain-dragged — to map every delaminated area, not just the ones that have already fallen off. Repairing only the visible damage is how a balcony ends up being scaffolded three times in five years, because the hollow areas beside the patch fail next.

Then removal, and it goes further than people expect. The concrete is broken out well past the edge of the damage and, critically, behind the reinforcement rather than just up to it, so the steel can be cleaned all the way around. Corrosion products are removed, the steel is treated or supplemented, and any bar that has lost too much section is replaced or spliced — that last judgement belongs to an engineer, not to a repair operator.

Rebuilding then restores the section and the cover, using a repair mortar with a bond coat, formed and compacted rather than smeared, and cured properly. The finish is matched as closely as practicable, which is the standard Queensland's guide sets, though an honest contractor will tell you that a repair will always be visible to a degree. Finally the cause is addressed: a leaking joint, a failed balcony membrane, a downpipe discharging onto the slab, or a fixing that broke the cover.

Concrete is a crystalline silica substance, and cutting, grinding and breaking it produces respirable dust. SafeWork NSW lists concrete among the materials containing crystalline silica and states a workplace exposure standard for respirable crystalline silica of 0.05 mg per cubic metre averaged over eight hours, and names cutting, sanding and drilling as activities that create the fine dust.

Since 1 September 2024 that work has been more tightly regulated. The Work Health and Safety Amendment (Crystalline Silica Substances) Regulation 2024 amended the New South Wales Work Health and Safety Regulation 2017 to provide for stronger regulation of the processing of materials containing crystalline silica across all industries, with additional duties where processing is assessed as high risk: worker instruction, information and training on the health risks, a silica risk control plan based on the risk assessment, air monitoring with results given to the regulator, and health monitoring for workers.

For a homeowner, the honest use of that is as a screening question rather than an obligation. Ask what dust control the contractor uses — on-tool extraction, water suppression, exclusion of the area — and whether they have assessed the processing. A contractor who breaks out a balcony soffit dry, on a suburban street, with no extraction, is showing you how they approach the rest of the job as well.

Patching is right when the damage is localised, the cause is identified and fixable, and the element is otherwise sound. It is the cheapest option and the one most likely to be recommended, which is exactly why the sounding survey matters — patching a mapped 20 per cent of a balcony soffit is a repair; patching the 5 per cent you can see is a deferral.

Resurfacing suits a slab whose surface has worn, dusted or pitted but whose reinforcement is intact and whose movement has stopped. An overlay or a bonded topping can give a new wearing surface without demolition. It is the wrong answer over active corrosion, because the corrosion continues underneath and will lift the new surface off in a few years.

Replacement becomes the sensible choice when the reinforcement has lost significant section over a large area, when the element has moved so far that the damage categories put it in the severe range, or when the cause cannot be fixed without taking the element apart anyway. That is an engineering judgement, and on a balcony, a suspended slab or anything structural, it should be made by a structural engineer rather than by the contractor who would be doing the repair.

Ask for the survey. A concrete repair quote should include the extent of delamination found by sounding, marked on a sketch or photograph, not just a square metre rate. Then the method: how far the breakout goes past the damage, how the steel is treated, what repair material is used, how the cover will be restored, how it will be cured and how the finish will be matched. And the cause: what is being done so it does not recur.

Where the concrete is structural — a balcony, a suspended slab, a beam, anything holding something up — get a structural engineer involved before the contractor, not after. The same applies where the slab forms part of a termite management system, because Queensland's guide is explicit that a repair to such a slab is defective unless the system is reinstated in accordance with the NCC.

Licensing is a state matter: Queensland runs a concreting licence class through the QBCC whose published scope is concreting including installing formwork, reinforcement and concrete, plus incidental work of another class, and New South Wales offers a licence check through Service NSW covering residential building work and the occupational trades. The Australian Consumer Law guarantees apply on top. Post photographs of the damage, including any rust staining, on LokalMatch and ask each contractor whether they intend to sound the whole element before quoting.