You've noticed black spots creeping across the bathroom ceiling. The kitchen window fogs up every morning. Your clothes smell musty even after washing. If you're renting in Australia, humidity and mould are not just cosmetic problems. They damage your health, your belongings, and your bond money. This guide walks you through the exact steps to identify, prevent, and fix mould in your rental home.
Why Humidity and Mould Are Worse in Australian Rentals
Australia's climate is humid. Sydney averages 65% humidity year-round, with coastal suburbs like Manly and Bondi hitting 75% or higher. Brisbane and Melbourne are even wetter. When you add poor ventilation, old plumbing, or a landlord who won't fix leaks, mould thrives.
Mould grows when moisture stays above 60% humidity for more than a few days. In a rental, you often can't control the building itself. You can't replace windows, install extraction fans, or fix rising damp. But you can control the moisture you create inside, and you can document problems for your landlord.
Health matters too. Mould spores trigger asthma, allergies, and respiratory infections. If you're a student, worker, or new migrant already adjusting to a new country, a mouldy home makes everything harder. You get sick more often. You sleep poorly. Your mental health suffers.
Spot the Problem Before It Spreads
Mould doesn't appear overnight. It starts small and spreads fast if you miss it. Learn where to look and what to do when you find it.
Where mould hides in rental homes
- Bathroom tiles, grout, and silicone seals around the shower
- Window frames and sills, especially on the south side of the house
- Under kitchen sinks and around pipes
- Bedroom corners where cold air meets warm air
- Inside wardrobes and cupboards with poor air flow
- Laundry areas and around washing machines
- Carpet edges and under rugs in damp rooms
Check these spots once a week. Use a torch and look closely at corners, seals, and fabric. Black or green spots, white fuzzy growth, or a musty smell are all signs.
What to do when you find mould
Small patches (less than 1 square metre) you can clean yourself. Large patches or mould inside walls need your landlord to act.
For small mould:
- Take photos and date them. You'll need these for your landlord.
- Spray the area with a 1:1 mix of white vinegar and water, or use a commercial mould killer like Dettol.
- Scrub with an old toothbrush or cloth.
- Wipe dry immediately.
- Leave the area to air dry completely.
For large mould or mould you can't reach:
- Take photos immediately.
- Write to your landlord or real estate agent in writing (email counts). Describe the location, size, and what caused it (e.g. "water leaking from the roof" or "condensation on the bathroom window").
- Ask them to fix it within 7 days. Under NSW tenancy law, landlords must keep rental homes in good repair and fit for habitation.
- If they don't respond, contact the NSW Fair Trading Rental Bonds Board or your state's equivalent.
Keep all emails and photos. These protect you if your landlord tries to claim mould damage against your bond.
Cut Moisture at the Source
The fastest way to stop mould is to stop creating excess moisture. You control this more than you think.
Ventilation: your first defence
Open windows for 10 minutes every morning, even in winter. This swaps humid indoor air for fresh outdoor air. Do this after showers, cooking, or using the washing machine.
If your rental has exhaust fans in the bathroom or kitchen, use them every time. Run them for at least 20 minutes after a shower or cooking session. Leave the door open so air flows out, not just around the room.
If there's no exhaust fan, ask your landlord to install one. It's a cheap fix (around $300-500) and they can claim it as a tax deduction.
Reduce moisture from daily activities
- Hang wet clothes outside or in a well-ventilated laundry, not in bedrooms or living areas.
- Wipe down shower walls and the bathroom mirror after every shower.
- Close the bathroom door while showering to contain steam.
- Use lids on pots while cooking to trap steam.
- Dry dishes in a rack rather than a cupboard.
- Don't use a clothes dryer indoors. If you must, vent it outside.
- Avoid using a humidifier (yes, even in winter).
These small changes cut indoor humidity by 10-15%. Over a week, that's the difference between mould growing and mould stopping.
Fix leaks and rising damp
If water is coming in from outside, no amount of ventilation will help. Leaks are your landlord's responsibility.
Signs of leaks or rising damp:
- Water stains on ceilings or walls
- Soft or spongy plaster
- Peeling paint or wallpaper
- A damp smell that doesn't go away even with ventilation
- Mould that comes back within days of cleaning
Report these in writing immediately. Take photos. Your landlord must fix structural problems within a reasonable time, usually 14 days for urgent repairs.
Control Temperature to Stop Condensation
Condensation is moisture in the air turning into water droplets on cold surfaces. It's the reason your bathroom mirror fogs up and your bedroom windows drip in winter.
You can't heat your entire home if your landlord won't pay for it. But you can be smart about where you heat and how.
Keep bedrooms and living areas warmer
Mould loves cold corners. If your bedroom is 15°C and the air is 80% humidity, condensation forms on walls and windows. If it's 18°C, humidity drops to 65% and mould stops growing.
Use a small heater in the bedroom during winter. A 2000-watt heater costs about $0.50 per day to run. It's worth it to avoid mould repair costs and health problems.
Insulate windows and pipes
Cold window frames attract condensation. If your rental has single-glazed windows, this is hard to fix without your landlord's help. But you can:
- Use thermal curtains or heavy drapes to trap warm air.
- Wipe condensation off windows every morning before it soaks into the frame.
- Leave curtains open during the day to let sunlight warm the glass.
Pipes under sinks also sweat in winter. Wrap them with foam pipe insulation (about $5 at Bunnings). This stops condensation forming underneath.
Protect Your Belongings and Your Bond
Even if you prevent mould, humidity damages your things. Protect what matters.
Store items safely
- Use plastic storage boxes instead of cardboard. Cardboard absorbs moisture and falls apart.
- Add silica gel packets or moisture absorbers to wardrobes and cupboards.
- Don't store items directly on the floor. Use shelves or boxes to allow air flow underneath.
- Leave space between items in wardrobes so air can circulate.
- Store important documents in a waterproof container.
Document the condition of your rental
When you move in, take photos of every room, especially any existing mould or damp. Send these to your real estate agent within 7 days. This protects you if your landlord tries to blame you for pre-existing damage when you move out.
Keep a log of any moisture problems you report. Write the date, location, and what you reported. Keep copies of all emails to your landlord.
When you move out, take photos again. If there's new mould that you caused (e.g. by not ventilating), your landlord can claim it against your bond. But if it's pre-existing or caused by structural problems, you have proof.
Know Your Rights as a Renter
In NSW, your landlord must keep the rental in good repair and fit for habitation. This means no mould from leaks, rising damp, or poor ventilation that the landlord can fix.
You must keep the rental clean and not cause damage. This means you need to ventilate properly and not create excess moisture.
If your landlord refuses to fix mould caused by structural problems, you can:
- Contact the NSW Fair Trading Rental Bonds Board for advice.
- Lodge a complaint with your state's tenancy tribunal.
- In serious cases, break the lease without penalty if the home is uninhabitable.
Other states have similar rules. Check your state's fair trading or tenancy authority for exact details.
Useful Official Sources
- NSW Fair Trading - Tenant rights, landlord obligations, and dispute resolution.
- NSW Health - Information on mould and health risks.
Frequently Asked Questions
Is mould in a rental home the tenant's responsibility or the landlord's?
It depends on the cause. If mould is from structural problems like leaks or rising damp, the landlord must fix it. If it's from poor ventilation or excess moisture you create, you're responsible for cleaning it. Always report mould in writing and take photos to prove who caused it.
How do I clean mould safely without damaging the rental?
For small patches, spray with a 1:1 vinegar and water mix or use a commercial mould killer, scrub gently, and wipe dry. For large patches or mould you can't reach, report it to your landlord in writing. Never use bleach on porous surfaces like grout, as it can damage them.
What humidity level is safe in an Australian rental home?
Keep indoor humidity between 40% and 60%. Above 60%, mould starts to grow. You can check humidity with a cheap digital meter from Bunnings (around $15). Ventilation and reducing moisture from cooking and showers are the fastest ways to lower it.
Can I break my lease if my rental has a serious mould problem?
In NSW, if mould makes the home uninhabitable and your landlord won't fix it, you may be able to break the lease without penalty. Contact NSW Fair Trading or your state's tenancy authority for advice before taking action.
Will mould damage my rental bond?
Yes, if you caused it through poor ventilation or excess moisture. Take photos when you move in to prove pre-existing conditions, and keep records of all mould reports to your landlord. This protects you at bond return time.
What's the cheapest way to reduce humidity in a rental?
Open windows for 10 minutes every morning, use exhaust fans while cooking and showering, hang wet clothes outside, and wipe down wet surfaces. These cost nothing and cut humidity by 10-15%. A small heater in winter costs about $0.50 per day and prevents condensation.
This is general information only. It is not legal, migration, financial, tax, medical, or professional advice. Always check official sources before acting.