Mould in a NSW strata apartment is a responsibility question before it is a cleaning one. If the moisture comes from common property, such as the roof, external walls, balcony waterproofing or shared plumbing, the owners corporation must repair the source; if it comes from inside your lot, such as your own shower, fittings or ventilation, it is yours. The strata plan and by-laws decide the boundary, and evidence of where the water is coming from decides the argument.
This is general information, not legal advice. Specific disputes should go to a strata lawyer, NSW Fair Trading or NCAT.
Common property or lot: the basics
NSW Government guidance on strata repairs and maintenance gives the general split. The owners corporation looks after common property, including the roof and gutters, boundary walls, the concrete floor slab, external plumbing, balconies and structural elements. Lot owners look after their own property, such as internal walls, carpet, plumbing fixtures and appliances. For water leaks, the source decides who pays: a leak from your property is yours, a leak from common property is the owners corporation’s.
The exact boundary varies by scheme. Check the registered strata plan and by-laws, or ask for the common property memorandum. In many buildings the boundary sits at the inner face of the external wall, so the wall itself is common property but the paint and plasterboard lining are not; windows and balconies are often where schemes differ.
Where strata mould usually comes from
Balconies. A failed balcony membrane that lets water into the unit below, or into a common ceiling, is usually a common property problem. Water ponding on your own balcony because of a cracked tile or blocked outlet may be yours, depending on the scheme.
Windows and external walls. Water entering around frames or through cracked render in rain is commonly a common property issue, though window ownership varies by scheme. Notify the strata manager in writing each time.
Shared drainage stacks. The vertical drain stack is normally common property; a leaking joint can wet several lots and the wall cavities between them. Which side of the connection has failed usually needs a licensed plumber to establish.
Exhaust fans. A bathroom fan that discharges into the ceiling void rather than outside fills the void with humid air and causes ceiling mould. Whether the ducting is common property depends on the scheme; see exhaust fan venting and mould.
Inside the lot. A leak from your own shower waterproofing or fittings, or condensation from a bathroom that is not ventilated, is generally the lot owner’s responsibility.
Water from the unit above
If the upstairs owner’s shower membrane or pipework has failed and water is coming through your ceiling, the upstairs owner is generally responsible for their fitting and may be liable for damage to your lot. If the water is coming through the slab or a shared stack, it is a common property issue. Photograph the damage as it happens, notify both the neighbour and the strata manager in writing, and ask the owners corporation to arrange an assessment. If you need water extracted and drying started quickly, see water damage and mould response.
Getting the owners corporation to act
The NSW Government’s strata guidance sets out the escalation where the owners corporation will not repair:
- Write to the strata manager. Describe the mould and its location, the likely source, and the repair you want. Attach dated photos and any inspection report.
- Put a motion to the next general meeting asking the owners corporation to investigate or approve the repair. Other owners affected by the same defect may support it.
- Apply for mediation with NSW Fair Trading. It is free. NCAT’s page on strata schemes orders says that for orders requiring mediation, you must attempt Fair Trading mediation before applying to the Tribunal.
- Lodge a complaint with Fair Trading if mediation fails; it can issue compliance notices or seek enforceable undertakings.
- Apply to NCAT to settle a dispute about repairs to common property.
If your lot was damaged because the owners corporation failed to repair common property, the same NSW Government page says you can take action for your loss, but only within six years of becoming aware of it. Do not withhold levies or start work on common property yourself; arranging your own repair and claiming it back is risky if responsibility is disputed. Get advice before spending money you hope to recover.
Newer buildings and defects
Mould in a relatively new building is often a construction defect, especially failed waterproofing. The NSW Government’s guidance notes a six-year statutory warranty period for residential buildings, a building bond for new buildings of four or more storeys, and complaints to Building Commission NSW about serious defects in buildings up to ten years old. If the owners corporation is not pursuing a defect claim, lot owners can press for it through general meeting motions.
Why an independent moisture report matters
Most strata mould disputes turn on where the water is coming from, and “it’s condensation” is a common first answer. An independent mould inspection and moisture assessment that maps moisture readings back to a source, such as an external wall, a balcony membrane or a stack joint, gives you evidence to take to the strata committee, mediation or NCAT. Enquiries through this site are passed to an independent local contractor who inspects and reports in their own name.
Tenants and insurance
A tenant in a strata unit deals with their landlord, not the owners corporation. The landlord must fix the problem under the tenancy, and pursues the owners corporation where the source is common property. The NSW rental mould disputes guide covers the tenant’s path.
For insurance, the owners corporation’s building policy usually responds to damage from a sudden insured event affecting the building, while a lot owner’s own policy covers contents and, depending on the policy, lot improvements. Gradual leaks through a defect are commonly excluded under both. The home insurance and mould guide explains the sudden-versus-gradual test.
Frequently asked questions
Who is responsible for mould in a strata unit in NSW?
The owners corporation if the moisture comes from common property such as the roof, external walls, balcony waterproofing or shared plumbing; the lot owner if it comes from inside the lot, such as their own shower or fittings. The strata plan and by-laws set the exact boundary.
The owners corporation says the mould is my fault. What can I do?
Get an independent assessment of the moisture source and put it to the strata manager in writing. If they still refuse, raise a motion at a general meeting, then apply for Fair Trading mediation, which is required before most NCAT strata applications.
Can I fix the mould myself and claim the cost from the owners corporation?
It is risky. Give the owners corporation written notice and a chance to repair first, and get advice before spending money you intend to recover, because responsibility may be disputed.
Can I claim compensation if common property damaged my lot?
NSW Government guidance says a lot owner can take action against the owners corporation for loss caused by its failure to repair, within six years of becoming aware of the loss.
What if water is leaking into my unit from upstairs?
If it comes from the upstairs owner’s fittings, such as their shower, they are generally responsible. If it comes through the slab or a shared stack, it is a common property issue for the owners corporation. Document it and notify both in writing.
If you need the moisture source in your apartment identified and documented, describe the problem and your suburb on the quote form and an independent local contractor can quote the inspection.