Mould in Your Apartment: Your Legal Rights When the Owners Corporation Won't Act

Mould in Your Apartment: Your Legal Rights When the Owners Corporation Won't Act

Mould is the slow-burn version of a strata problem. A leak floods your bathroom and you know within hours. Mould creeps along a wall, behind a wardrobe, beneath the carpet — and by the time you see it, you have been breathing the spores for months. Asthma worsens. Children develop coughs that don't resolve. Personal items become unsalvageable. And the owners corporation tells you, often, that the mould is your problem to manage.

In most cases, this is wrong. Mould in apartments is overwhelmingly caused by water — water leaks, condensation, inadequate ventilation, failed waterproofing — and water issues in strata buildings are overwhelmingly the responsibility of the owners corporation. Recent decisions of NCAT and VCAT have made this position increasingly clear, and the compensation available to affected owners now extends well beyond the cost of cleaning the mould itself.

This article walks through what causes mould in strata buildings, who is legally responsible, what compensation you can claim, and what to do when the OC refuses to act.

What Actually Causes Mould in Apartments

Mould requires three things: moisture, organic material to grow on, and temperatures above about 5°C. In an Australian apartment, the second and third are always present. The variable is moisture.

The four primary moisture sources, in roughly the order of frequency, are leaks from common property (failed waterproofing membranes in bathrooms above, blocked common drains, deteriorated façade sealing, defective roofing), condensation caused by inadequate ventilation (poorly designed bathroom and kitchen exhausts, sealed windows in bedrooms, ducted air conditioning that does not handle humidity), thermal bridging through external walls (older buildings without insulation, where cold external walls draw moisture from internal air), and leaks from neighbouring lots (washing machine overflows, internal plumbing failures, balcony drainage failures in the apartment above).

The first three of these are common property issues. The fourth is sometimes a lot owner issue, sometimes common property — and the distinction matters legally.

A specialist mould inspection report is often necessary to establish which category the problem falls into. A mould species analysis, combined with a moisture mapping survey of the affected walls and ceilings, will typically identify the source within a few hours of investigation. The cost of such a report is usually $400-$800 and is recoverable from the OC if common property is found to be the cause.

The Legal Framework: Why Mould Is Usually the OC's Problem

In NSW, section 106 of the Strata Schemes Management Act 2015 imposes a strict duty on the owners corporation to maintain and repair common property. The duty applies regardless of fault, regardless of the OC's financial position, and regardless of whether the OC knew about the defect.

In Victoria, section 46 of the Owners Corporations Act 2006 imposes an equivalent duty. In Queensland, the Body Corporate and Community Management Act 1997 contains similar provisions, with the precise scope depending on the format plan. In every Australian jurisdiction, the principle is consistent: the OC is responsible for the structural fabric of the building and for any common property element that contributes to a moisture problem.

When mould is caused by a failed waterproofing membrane, by inadequate ventilation built into the original construction, by façade sealing that has deteriorated, or by any defect in shared plumbing, the OC's duty engages. The owner is not required to prove that the OC was negligent or unreasonable. The owner only needs to establish that the moisture source is on common property.

The owner is required to mitigate their own loss. Once the moisture problem is identified, the owner must take reasonable steps to prevent further damage — moving furniture, turning off any contributing internal source, allowing the OC's contractors access to investigate. Failure to mitigate can reduce the compensation a Tribunal will award.

What You Can Recover

The compensation available where mould is caused by common property is broader than many owners realise.

The first category is repair and remediation costs. This includes the cost of professional mould remediation by a licensed contractor, replacement of affected materials (carpets, plasterboard, tiles, joinery), and any structural works required to address the moisture source.

The second category is replacement of damaged personal property. Mould-affected clothing, furniture, mattresses, books, and electronics are often unsalvageable. The OC's strict liability extends to the value of these items, subject to the obligation to mitigate.

The third category is alternative accommodation. Where the apartment becomes uninhabitable during remediation, the OC is liable for the cost of alternative accommodation for the period the owner cannot reasonably live in the unit. For investor owners, this becomes lost rent.

The fourth category is health-related expenses. Where mould exposure has caused or worsened a medical condition, the cost of medical treatment, time off work, and related expenses can be claimed. Establishing the causal link generally requires medical evidence, but where the link is documented, Tribunals have awarded compensation.

The fifth category is expert and legal fees. The cost of mould inspections, building consultants, and (in NCAT proceedings) legal representation is recoverable in many cases.

The sixth category is general damages for loss of amenity. This is the smallest of the categories and is awarded sparingly, but recent NCAT decisions have included modest amounts for the disruption and stress of dealing with prolonged mould issues.

What to Do When the OC Won't Act

The procedural pathway is well established. Most cases resolve before reaching the Tribunal — but only if the owner follows the right steps in the right order.

The first step is documentation. From the moment mould is identified, photograph everything. Date-stamp the photos. Record the date the mould first appeared. Save communications with the OC and the strata manager. Keep receipts for any expenditure. The documentary record is what determines the strength of any subsequent claim.

The second step is professional inspection. Engage an independent mould or building consultant to identify the moisture source and produce a written report. Provide the report to the OC immediately, formally, in writing. The report converts a vague complaint ("there is mould in my apartment") into a specific allegation against common property ("the bathroom waterproofing membrane on level 4 has failed and is causing mould in apartment 304").

The third step is a formal demand. Write to the strata manager and the committee, attaching the report, identifying the section of the relevant Act that applies, requesting that the OC carry out remediation works within a specified period (typically 14-28 days for an initial response), and reserving the right to claim compensation. Send the demand by email with delivery confirmation, and follow up if no response is received.

The fourth step is mediation. In NSW, mediation through Fair Trading is free and is required before NCAT will hear most strata disputes. In Victoria, conciliation through Consumer Affairs Victoria performs the same function. In Queensland, the BCCM Commissioner's office mediates. Mediation typically takes 6-8 weeks to schedule and resolves a substantial proportion of disputes — usually because the OC's solicitor explains, plainly, that the OC will lose at the Tribunal.

The fifth step is the Tribunal. Applications can be self-represented, attract a modest filing fee, and are heard within 4-6 months. The Tribunal can order the OC to carry out specified works, pay compensation, and in extreme cases, appoint an administrator.

The sixth step, available in NSW since October 2025, is a complaint to NSW Fair Trading under the expanded enforcement powers. Fair Trading can investigate, require documents, issue compliance notices, and seek enforceable undertakings. This is the appropriate path where the OC has ignored Tribunal orders or where there is a pattern of failure.

Recent Tribunal Decisions

The pattern of decisions over the past three years has been consistently in favour of owners where common property is the moisture source.

NCAT decisions in 2024 and 2025 have ordered owners corporations to fund mould remediation, replace affected materials, fund alternative accommodation for periods of months, and pay compensation for personal property losses. The March 2026 Appeal Panel decision concerning bathroom waterproofing affirmed the strict liability principle in clear terms — the OC's argument that it had been "doing its best" with limited funds was rejected.

VCAT decisions have followed a similar path. Where the moisture source is established and the owner has acted reasonably, the OC's liability is rarely successfully resisted.

The cases that the OC wins are generally those where the owner failed to mitigate, where the moisture source was inside the lot rather than on common property, or where the owner could not produce a credible inspection report identifying the source.

What Committees Should Be Doing

For committees, the pattern is the same as with leaks: early intervention prevents most disputes. The OC that commissions a mould inspection within days of a complaint, acts promptly on the findings, and communicates clearly with the affected owner avoids almost all of the contested outcomes.

The OC that delays — for budget reasons, because a single committee member is sceptical, because the strata manager has not pushed the matter — exposes the building to claims that are larger than the original repair cost.

The starting point is treating any reported mould as a potential breach of the OC's duty. The OC should commission a moisture and mould inspection within seven days of a complaint. If the source is common property, repairs should be authorised without waiting for legal pressure. If the source is in a lot or in a neighbouring lot, the OC should communicate this clearly with evidence.

The second step is reviewing the building's broader moisture risk profile. Mould complaints in one apartment are often a symptom of a building-wide issue — inadequate ventilation in original construction, failed waterproofing in multiple bathrooms, façade sealing approaching the end of its design life. A single complaint should prompt a wider review.

The third step is documentation. Every report, every inspection, every repair decision should be logged. The OC's documentary record is what determines whether a Tribunal accepts that the OC acted reasonably.

The State-by-State Picture

The framework is broadly consistent across Australian jurisdictions, with some procedural variation.

How UnitBuddy Helps

UnitBuddy's defect tracking module captures every mould report with photos, inspection findings, communications, and repair decisions, and surfaces the OC's response time as a governance metric. The system flags any defect that has been open beyond the OC's policy threshold, produces the documentary record required for Tribunal proceedings, and gives owners visibility over what the OC is actually doing about reported issues.

For committees, the platform converts what is often a fragmented email trail into a clear, time-stamped record — the difference, in many cases, between a successful defence at Tribunal and a costly award against the OC.

Mould is rarely just a cleaning problem. It is almost always a moisture problem, and moisture problems in strata buildings are almost always the OC's responsibility. The owners who get this right are those who act early, document carefully, and treat the legal framework as the genuine source of leverage it actually is.