Who is responsible for concrete cancer in a strata building? In most cases, the owners corporation. Under section 106 of the NSW Strata Schemes Management Act 2015, the owners corporation has a strict duty to properly maintain and keep common property in a state of good repair — and carparks, balcony structures, and shared building elements are almost always classified as common property. This isn’t general guidance you should rely on without checking your own scheme’s by-laws and getting advice specific to your building, but as a starting point, if the concrete cancer is in a shared carpark or in the structural balcony slab (as opposed to, say, a lot owner’s balcony tiling or balustrade), it’s the owners corporation’s responsibility to act.
That said, “who’s responsible” is only the first question. What follows — how it gets funded, how it gets scoped, and how it gets delivered without turning residents’ lives upside down — is where most strata committees actually need help.
Why carparks and balconies are the highest-risk areas
Concrete cancer can appear almost anywhere in a building, but in our experience working across Western Sydney strata properties, two locations come up again and again: carparks and balconies.
Carparks are exposed to a specific combination of moisture sources — water tracked in on vehicles, drainage from the levels above, condensation, and in some buildings, direct water penetration through construction or waterproofing defects. The underside of carpark slabs, where the reinforcing steel sits closest to a damp, low-airflow environment, is a classic location for advancing corrosion. It’s also one of the more serious ones from a safety perspective, because deteriorating concrete overhead in an occupied carpark is a falling-hazard risk, not just a maintenance issue.
Balconies fail for a related but distinct reason: waterproofing membrane failure. Balcony slabs are directly exposed to weather, and if the membrane beneath the tiles or surface finish has degraded, cracked, or was installed incorrectly in the first place, water finds its way to the structural slab and the reinforcing steel beneath. Once that starts, it typically progresses regardless of how well the visible tiled surface looks.
Both locations share a common thread: by the time damage is visible, the underlying corrosion has usually been active for a while.
Working out who’s responsible: a simple way to think about it
Strata by-laws vary between schemes, so this isn’t a substitute for checking your own scheme’s registered by-laws, but the general starting logic looks like this:
Step 1: Is the affected concrete common property? Structural slabs, carpark structures, external walls, and the structural component of a balcony (as distinct from finishes a lot owner has added) are typically common property under the standard strata plan.
Step 2: If it’s common property, the owners corporation’s section 106 duty applies. The owners corporation must properly maintain and repair it — this is described in case law as a strict, largely non-discretionary obligation, not something that can simply be deferred indefinitely for cost reasons.
Step 3: Check whether a lot owner’s by-law variation shifts responsibility for a specific element. Some schemes have by-laws that shift responsibility for certain balcony finishes (tiles, balustrades installed by a lot owner) to the individual lot owner, while the structural slab itself remains common property.
Step 4: If there’s a dispute about classification, get advice. Where it’s genuinely unclear whether an element is common property or part of a lot, a strata lawyer or NSW Fair Trading/NCAT guidance is the appropriate next step, not a decision to make informally at a committee meeting.
How capital works planning fits in
Once concrete cancer repair is identified as a common property responsibility, the next question is funding. This is where the 10-year capital works fund plan, required under section 80 of the Strata Schemes Management Act 2015, becomes relevant.
If your scheme’s capital works plan already anticipated concrete or waterproofing remediation, funding the repair may be a matter of drawing on the existing fund, potentially combined with a special levy if the identified cost exceeds what’s been set aside. If the plan didn’t anticipate the issue — which is common, since concrete cancer often isn’t visible until it’s already progressed — the committee will typically need to commission a proper assessment, get a scoped quote, and then put a special levy or a revised capital works contribution to owners for approval.
This is also a good moment to get the 10-year plan reviewed and updated, since section 80 requires it to be reviewed at least every five years in any case, and a concrete cancer finding is a natural trigger to bring that review forward.
Managing the disruption to residents
This is usually the practical concern that worries a strata committee most, understandably. A few things genuinely help:
Staging the work zone by zone rather than closing an entire carpark or all balconies at once, wherever the scope of damage allows it. Clear, early communication to owners and residents about what’s happening, why, expected noise and access impacts, and realistic timing — vague updates create more anxiety than detailed ones. Scheduling noisier work (breakout, demolition) within reasonable hours and giving residents specific notice rather than a general date range. Providing alternative parking arrangements where carpark bays are affected, even if temporary and imperfect.
None of this eliminates disruption entirely — structural concrete repair is inherently disruptive — but a contractor experienced in occupied strata buildings will have a genuine staging and communication plan, not just a start date and an end date.
Frequently asked questions
Will owners have to pay a special levy for concrete cancer repair?
Often, yes, unless the capital works fund already has sufficient funds allocated. The exact mechanism — special levy, increased regular contribution, or drawing down existing capital works funds — depends on your scheme’s financial position and is a decision for the owners corporation at a general meeting.
How long does concrete cancer remediation typically take in a strata building?
This depends heavily on scope. Isolated repairs in a small area might take one to two weeks. Remediation across a full carpark or multiple balconies commonly runs from several weeks to a few months, and larger-scale, multi-building remediation projects can extend well beyond that.
Can the committee be held liable for delaying repairs?
Given the strict nature of the section 106 duty, an owners corporation that’s aware of a defect and unreasonably delays addressing it can potentially expose itself to a claim from an affected lot owner. This is a matter for your strata lawyer to advise on for your specific circumstances, but it’s a meaningful reason not to sit on a known concrete cancer finding.
Do all balconies in a building need to be inspected once one is found to have concrete cancer?
It’s a reasonable and common precaution. If one balcony has failed waterproofing or advancing corrosion, others built to the same original specification and exposed to similar conditions are at elevated risk, and a building-wide assessment is usually the sensible next step.
Stakat Building works with strata managers and owners corporations across Sydney on concrete cancer assessment and remediation in carparks, balconies, and common property structures, including staged programmes designed to minimise disruption to residents. If your committee is dealing with a concrete cancer finding and needs a clear scope and cost picture before the next general meeting, we’re happy to help.