Concrete Crack Repair & Water Ingress in Sydney
Water is what starts most concrete cancer and what restarts it after a repair. Cracks, failed waterproof membranes and blocked drainage are the routes it takes, and fixing the concrete without fixing the route puts the same repair back on the same balcony.
What concrete cancer repair in Sydney actually involves
Not every crack is concrete cancer. Shrinkage cracking in a slab is common and often harmless; a crack that is leaking, staining or lifting the surface next to it is a different matter. The pattern worth acting on is a crack with rust colour coming out of it, or white crusty deposits along it — efflorescence, which is salts carried out of the concrete by water moving through it, and which means water is moving through it.
Finding the route the water takes
On balconies the usual route is a waterproof membrane that has reached the end of its life under a tiled surface. Water gets past the tiles, sits on a membrane that no longer sheds it, finds the slab edge or a penetration, and works its way to the reinforcement. Lifting a corner of the covering is often how it is confirmed. The fix is a membrane and a fall that actually drains, not a sealant along the crack.
Where a repair has already been done and the water was not addressed, the same bar corrodes behind the new mortar and the repair fails at its edges. This is the most common reason a building has two generations of patch on the same balcony — the second one done because the first one was only ever half the job.
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. Published guide bands for concrete repair are on the pricing page. They are not quotes, 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.
Concrete Crack Repair & Water Ingress in Sydney — common questions
Is efflorescence a problem in itself?
The white deposit is not damaging on its own — it is a symptom. It means water is moving through the concrete and coming out somewhere, and that water is what corrodes reinforcement. Treat it as a sign to find the route rather than as something to scrub off.
Can the membrane be replaced without lifting the tiles?
Generally not, if the membrane is under them. A liquid-applied membrane over the top of an existing tiled surface is sometimes offered; whether it is appropriate depends on what is underneath and where the water is currently going, which is an inspection question rather than a product question.
The balcony was repaired a few years ago and it is spalling again — why?
Most often because the water was never addressed. A repair that treats the concrete but leaves the membrane, the fall or the drainage as they were puts the same bar back in the same conditions, and it fails at the edges of the previous patch. Two generations of patch on one balcony is the common pattern.
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