Concrete Cancer & Spalling Repair in Sydney
Spalling is repaired by removing the damaged concrete back to sound material, cleaning and treating the exposed reinforcement, and reinstating with a repair mortar. Every step before the last one is invisible in the finished job, which is why the finished job is not what to judge it by.
What concrete cancer repair in Sydney actually involves
Concrete cancer and concrete spalling describe the same failure. Reinforcing steel inside the slab corrodes; rust occupies several times the volume of the steel it replaces; the pressure cracks the concrete cover and pushes it off. On a balcony that usually appears first at the slab edge or on the soffit underneath, as a crack, then a rust stain running down the face, then a piece of concrete on the ground.
Breakout, treat, reinstate
The repair sequence is breakout, treat, reinstate. Damaged concrete is cut back past the corrosion until sound material and clean steel are reached — which is nearly always further than the visible damage suggests, because the corrosion travels along the bar. The reinforcement is cleaned back to bright metal and coated. Repair mortar is packed into the recess and finished. Where the cause was water getting in, the water has to be dealt with too, or the same bar rusts again behind the new mortar.
This is why patching does not hold. A cosmetic patch over corroding steel hides the stain for a season and leaves the mechanism running. The tell is a repair that fails at its own edges within a year or two — the sound concrete next to the patch spalling next, because the bar was never treated where it continued.
What concrete cancer repair costs in Sydney
| Job | What it covers | Typical range |
|---|---|---|
| Minor work — guide A (Atomic Projects) | Two current published guides give a per-square-metre rate for minor concrete cancer work, and they disagree by about three times on the same description. This is the lower of the two. | A$250–600 |
| Minor work — guide B (awesim) | The same job, the higher published rate. Neither guide is wrong and neither is a quote for your building — the gap between them is the reason a real number follows an inspection. | A$700–1,500 |
| Severe or structural repair | Both guides publish the same band here — the one figure on this page the two sources agree on. | A$1,200–2,500 |
| Extensive beam or column repair | The upper band from the guide that publishes one. Structural elements rather than a balcony edge. | A$2,000–4,000 |
Ranges reflect typical Sydney jobs and vary with access, site conditions and scope. Bands published in two current Sydney and NSW cost guides, shown separately because they disagree. Not a quote for your building. A firm price comes from a site visit — call (02) 9072 0403 or use the quote form.
Concrete Cancer & Spalling Repair in Sydney — common questions
How do I know if it is concrete cancer or just a crack?
Rust staining is the difference worth looking for. A crack with a brown stain running out of it, or a patch of soffit that sounds hollow when tapped, is the pattern. Hollow concrete is found by sounding rather than by eye, which is why an inspection marks out a bigger area than a photograph suggests.
Is my balcony dangerous?
Concrete falling from a soffit is the case to treat as urgent, because the piece that falls lands somewhere. If material has already come away from an overhead surface, keep people out from underneath it and get it looked at rather than waiting for the next piece.
How long before it needs doing again?
Not in the repaired area, if the reinforcement was cleaned back to bright steel, treated and properly re-covered, and whatever was letting water in was dealt with at the same time. Elsewhere on the same building is a different question — the rest of the structure is the same age and has had the same exposure.
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