Concrete Cancer & Spalling Repair in Sydney — questions and answers
The questions below come up on nearly every call. Where two published sources disagree, both are shown.
Call (02) 9072 0403Cost
How much does concrete cancer repair cost in Sydney?
Two current published guides agree on severe or structural work at A$1,200–2,500+ per square metre, and disagree on minor work, where one publishes A$250–600 per square metre and the other A$700–1,500 per square metre. That is roughly a threefold gap on the same broad description. Whole-job figures from one of the two run from about A$1,500–5,000 for cosmetic spalling reachable from a ladder up to A$40,000 and beyond for a building-wide programme, with scaffolding alone able to exceed A$15,000. None of those is a quote for your building.
Who pays in a strata building — the owner or the owners corporation?
It depends on whether the affected element is common property or part of the lot, and that boundary is the thing to establish before anyone quotes. In a Class 2 building the structural slab is generally common property even where a balcony is used exclusively by one lot, which usually puts the repair with the owners corporation rather than the owner — but the answer is set by the strata plan and the by-laws for that building. NSW Fair Trading publishes guidance on the common property boundary, and your strata manager will have the plan.
| 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. The published guide bands quoted in these answers are on the pricing page in full. None is a quote, and neither source states how GST is treated. A firm price comes from a site visit — call (02) 9072 0403 or use the quote form.
Process
Does patching or painting over it work?
No, and it usually makes the next repair bigger. Painting over a stain leaves the reinforcement corroding behind it, and the corrosion continues along the bar past the patch. The tell is a repair that fails at its own edges within a year or two, taking the sound concrete beside it.
Will it come back?
Not in the repaired area if the reinforcement was properly cleaned, treated and re-covered and the water that started it was dealt with. It can appear elsewhere on the same building, because the rest of the structure is the same age and has had the same exposure. That is why a scope on an older block often covers an elevation rather than a single balcony.
Timing
How quickly can someone get to me?
Form and phone enquiries are passed to a local provider, who contacts you directly. Whoever calls you back works the corridor your building sits in, because the Eastern Suburbs, the Northern Beaches, the Shire and the North Shore are four different jobs.
Is concrete cancer structural, and how urgent is it?
It is corrosion of the structural reinforcement, so it is structural by definition — but the urgency depends on where it is and how far it has gone. The case to act on immediately is spalling on an overhead surface: a soffit shedding concrete drops it on whatever is below. Keep people out from under it and get it inspected rather than waiting to see whether more comes away.
Permits and approvals
Do I need an engineer?
Sometimes, and it is a scope question rather than a formality. Where reinforcement has lost enough section to matter, or where the repair is to a structural element such as a beam or column rather than a slab edge, a design is needed rather than a method. On Class 2 buildings the NSW Design and Building Practitioners scheme requires a regulated design produced by a registered design practitioner and lodged on the NSW Planning Portal, which puts an engineer in the process by law rather than by choice.
Source: NSW Government guidance on remedial building work in regulated buildings
Service area
Which suburbs do you cover?
Sydney's Eastern Suburbs, Northern Beaches, Sutherland Shire, Lower North Shore and Inner West — Bondi through Maroubra, Manly through Narrabeen, Cronulla and Caringbah, and Mosman through Marrickville.
What is magnesite, and why does it come up?
Magnesite is a floor topping laid over concrete slabs in a lot of mid-century Sydney unit blocks — you may see it as a hard, sandy-grey layer under the floor covering, often on balconies and landings. Where it is present and has been getting wet, it is associated with corrosion of the slab reinforcement underneath it, and an inspection of an older block will usually check for it. Whether it is the cause in a particular building is something the inspection establishes, not something to assume from the era.