Mould Prevention in Sydney Rentals

Mould is one of the most contentious issues in Sydney rentals — and one of the most common. Sydney's humid subtropical climate, combined with older housing stock and tight apartment ventilation, creates ideal conditions for mould growth. And when it appears, the question of who is responsible and what to do about it is rarely straightforward.

This guide covers how mould forms, where to find it first, how to prevent it, how to clean it safely, and what your rights are as a NSW tenant.

Why Sydney is Particularly Prone to Mould

Mould spores are always present in the air — the question is whether conditions allow them to colonise. They need three things: moisture, a surface to grow on, and warmth. Sydney's climate delivers all three for much of the year:

• Average relative humidity in Sydney sits between 60–70% year-round, peaking in summer (December–March)
• Coastal proximity and humid winds mean even well-ventilated apartments can struggle during extended humid spells
• Older construction (pre-1990s) often lacks adequate ventilation, sarking, or cavity insulation — making internal condensation far more common
• Small apartments with poor cross-ventilation create stagnant air pockets where moisture accumulates

Where Mould Appears First

These are the areas to check regularly — particularly in the early warning stage when small black or grey spots first appear:

Prevention: The Daily and Weekly Habits That Matter

Most bathroom and kitchen mould is preventable with consistent ventilation habits. These are the habits that make the biggest difference:

• Run the exhaust fan every time you shower — leave it running for at least 10 minutes after you finish. If there's no exhaust fan, open the window and door to create airflow.
• Wipe down shower walls after use — a squeegee takes 30 seconds and dramatically reduces surface moisture that mould needs.
• Keep the bathroom door open after showering to let moisture escape into the rest of the dwelling.
• Run the rangehood when cooking, especially when boiling or frying — these activities release significant steam.
• Don't dry clothes indoors without ventilation — a full load of laundry releases approximately 2 litres of moisture into the air as it dries. If you must dry indoors, open a window.
• Leave a gap between furniture and external walls — especially wardrobes and bed heads. At least 5cm allows air to circulate and prevents moisture buildup behind furniture.
• Check under sinks monthly — slow drips under kitchen and bathroom sinks are common and often undetected for months.

How to Clean Mould Safely

For small surface mould patches (under approximately 1 sqm), you can treat it yourself. For larger infestations, or mould that keeps returning despite treatment, professional remediation is safer and more effective.

What you'll need: white vinegar in a spray bottle, microfibre cloths, rubber gloves, an N95 mask, and safety glasses.

1. Ventilate the area — open windows and run the exhaust fan before you start.
2. Wear your protection — gloves, mask, and eye protection. Mould spores become airborne when disturbed.
3. Spray white vinegar generously onto the affected area and leave it for 30–60 minutes. Vinegar kills approximately 82% of mould species and is safe for most surfaces.
4. Scrub with a stiff brush for grout and textured surfaces. Use a cloth for smooth surfaces like tiles and painted walls.
5. Wipe dry thoroughly — leaving moisture behind defeats the purpose.
6. For stubborn grout mould, a paste of baking soda and water applied with a toothbrush and left for 10 minutes before scrubbing is effective.
7. Dispose of cloths — don't rinse and reuse; seal them in a bag and bin them.

Your Rights as a NSW Tenant

Under NSW tenancy law, mould responsibility depends on its cause:

• If mould is caused by a building defect (roof leak, inadequate ventilation, rising damp, faulty exhaust fan) — the landlord is responsible for remediation and the underlying repair.
• If mould is caused by tenant behaviour (not ventilating, drying clothes indoors without airflow) — the tenant may be responsible for cleaning costs.
• Where cause is disputed, landlords cannot simply blame the tenant without evidence.

If you discover mould caused by a building issue, notify your property manager immediately in writing (email is sufficient) and document with dated photos. Under NSW law, landlords must address building maintenance issues within a reasonable timeframe. If they don't, you can escalate to the NSW Civil and Administrative Tribunal (NCAT).

Important: never let a landlord deduct bond for mould remediation caused by a building defect. Photograph everything.