How to stop mould from growing in your home

mould growing on wall with cleaning products in front

Danny Baggs

Posted October 31, 2022

Mould can cause major damage to your home if not properly prevented...and once it’s there, mould is notoriously hard to get rid of. Here’s how to effectively safeguard your home from mould.

Victoria has seen all sorts of weather patterns in the last few years, from cold and damp winters to flood-prone summers – both of which can cause excess moisture in the air and in the home. This excess moisture has the potential to cause mould on both indoor and outdoor surfaces. 

“There’s a risk that mould may develop any time an area of your home is allowed to stay wet for an extended period,” says Head of RACV Trades Kieran Davies. Mould typically grows on walls and wallpaper, in wardrobes on clothes, in bathrooms, carpets, kitchens, books, insulation material, wood, and any other surface that doesn’t have proper ventilation, according to Davies.

With Victoria experiencing more wet weather thanks to the return of La Niña, as well as a negative Indian Ocean Dipole event, there has never been a more important time to protect your home from mould. 

Mould in the home can be a much bigger problem than people think. “While mould is particularly concerning due to the health impacts on occupants, the unsightly marks may require re-plastering or painting affected areas,” Davies says. “Associated moisture can also cause significant damage and rotting to the timber structure of the roof or floor of a home and other wood like weatherboards.”

What is mould?

Mould is a type of fungus that grows and spreads on damp, poorly ventilated areas. Although mould originates from plant and animal matter, its reproductive spores become airborne and can float indoors. “Mould spores thrive on damp, moist or warm surfaces,” Davies says.

While "black mould" is often associated with toxic health risks, the colour of mould isn't an indicator of its danger. "Black mould" can refer to several species of mould that are dark green or black, such as Stachybotrys chartarum.

The more common types of mould to appear in the home are:

  • Alternaria – occurs in damp indoor spaces, such as in showers or under leaky sinks

  • Aspergillus – often grows indoors on dust, powdery food items, and building materials like drywall

  • Cladosporium – can grow in cool or warm areas, tending to appear on fabrics and wood surfaces

  • Penicillium – tends to grow on materials with water damage; usually blue or green in appearance.


mould growing in a windowsill

Mould is a type of fungus. Image: Getty

What does mould look like?

“Mould can look quite different depending on where it grows, as well as the type of mould it is,” says Davies. “Keep an eye out for white, black, yellow, blue, or green spots that look like a stain on the surface.” Rarer moulds can appear grey, orange or brown.

How to stop mould in your home

The best way to reduce mould in the home is to minimise moisture in all areas, according to Davies. “Since poor ventilation is one of the main causes of mould, the best thing to do is ensure you have as much ventilation as possible throughout the home, under the floors, and in the roof.”

Purchasing dehumidifiers for any humid areas of your property is one of the best ways to stop mould from forming. Dehumidifiers can help absorb excess moisture from the air, improve air circulation and quality, and reduce allergens like dust. These benefits create an inhospitable environment for mould to thrive. Air purifiers can help further by filtering mould spores out of the air, effectively stopping reproduction – but it won’t treat active mould growing on surfaces.

How to stop and prevent mould in the bathroom

Proper waterproofing can help prevent mould in the bathroom. “It’s essential that all bathrooms are correctly waterproofed and that the roof is weathertight,” Davies says.

Grout mould – the kind that blackens the white lines between your bathroom tiles – is particularly prevalent in domestic bathrooms. To help prevent grout mould, you can:

  • Regularly clean your bathroom with safe antifungal solutions that also get rid of soap scum (soap residue that allows mould to thrive)

  • Keep the shower door, bathroom door and any bathroom windows open after showering to air out the space

  • Install an exhaust fan and leave it on during your shower and for about 20 minutes afterwards

  • Reseal the grout once or twice a year after a thorough clean and dry.

Fixing leaking plumbing and ensuring all water is dried up after showering or using the bath can also make a difference,” says Davies.

To avoid mould from growing on your bathmat and towels, choose materials that are easily washable and regularly launder them. Keep fabrics dry between showers by hanging them up properly. Likewise, dry your shower curtain between showers and regularly wash it.


mould growing in a shower

Mould is common in domestic bathrooms, especially on shower tiles. Image: Getty

How to stop and prevent mould in the laundry

When it comes to the laundry, the type of dryer you have can make a big impact on moisture levels. Heat pump clothes dryers typically don’t need ducted venting to prevent mould, because they recycle the warm air they produce. Condenser dryers, on the other hand, produce a lot of high-heat air that needs to be properly ventilated to prevent mould.

Turning on any exhaust fans when the dryer is in use can help funnel the resulting hot, moist air out of the room. If you have a European-style laundry (washer/dryer tucked behind doors in a cupboard-like space), keeping the doors open while the dryer is running can also help.

A dehumidifier is another great investment to reduce moisture in the air in the laundry.

How to stop and prevent mould on windows

A great way to prevent mould on windows is to dry off condensation. “On cold mornings, give the windows a wipe with a soft, clean cloth to remove excess moisture,” says Davies. “It’s also a good idea to open the windows and allow airflow, which naturally removes dampness from the air.”

Cleaning your windows with vinegar is another great way to kill mould and bacteria living on glass surfaces. You can make your own cleaner by distilling white vinegar into a spray bottle and spraying directly onto the surface, then wiping clean with a microfibre cloth.


Chelsea Smith from The Organising Platform demonstrates how to make eco-friendly cleaning sprays and scrubs using natural, everyday ingredients.

How to stop and prevent mould in the wardrobe

Finding mouldy spots on your clothes can be frustrating, but there are a few steps you can take to ensure mould doesn’t creep into your wardrobe. 

Ensuring that your clothes are completely dry before putting them away is key. “When damp clothing meets cold internal surfaces like the ceiling or walls of the wardrobe, tiny water droplets will collect on the cold surfaces as the air cools, causing patches of mould to grow,” Davies says.

Allowing clothes to ‘breathe’ in your wardrobe – meaning, not jamming your closet to the brim and allowing air to flow through from your bedroom – will also help prevent moisture, as well using a dehumidifier to keep walls, ceilings and clothes dry.

How to stop mould in the bedroom

Much like the wardrobe, the best way to stop mould in the bedroom is preventing dampness. Leaving wet objects (like raincoats or umbrellas) on chairs, beds or carpets makes moist surfaces that can lead to mould spots. Opening bedroom windows (and/or balcony doors if you have them) is another simple action that promotes air flow and dries up dampness. 

“Fresh air is a great and cheap way to get ventilation through the home,” Davies says. “It can be unpleasant during the depths of winter, but opening doors and windows for even an hour a day can dry up a lot of moisture.”

Ensuring heating and cooling systems are regularly maintained is another way to reduce mould in bedrooms. That’s because air conditioner and heater filters can become clogged with dust, bacteria and mould over time. When you switch on a dirty air conditioner, it could pump out contaminated air and shoot mould spores all over the room. RACV Trades can service your heater or air conditioner.

How to stop mould growing on house foundations

Completing jobs around the house like cleaning gutters, fixing leaky pipes and maintaining roofs can have a big impact on whether water drains properly or whether it accumulates and causes dampness, leading to mould.

Leaking pipes is a leading cause of ‘rising damp’: oversaturated ground beneath your house that forces stone, brick and mortar in your foundation and subflooring to soak up the water and start growing mould. Get leaky pipes professionally fixed as soon as possible to mitigate the risk of rising damp.

Always take care working at height on a ladder and use safety equipment such as gloves and non-slip shoes. Seek professional help for any job beyond your level of skill on a ladder or physical ability.


How do I stop mould as a renter?

Landlords are required to provide a property that is free from mould and damp. If mould forms during your tenancy because of a property defect – such as the property not having adequate ventilation or the building having structural damage that caused rising dampness – then it is the landlord’s responsibility to remedy. In addition, if mould forms very soon after your tenancy begins, it could be considered a pre-existing problem.

On the other hand, you may be liable for mould removal costs if you didn’t take reasonable steps to prevent mould during  your tenancy. Luckily, you can follow most of the above advice for preventing mould, such as wiping down condensation-heavy windows with a microfibre cloth, turning on the bathroom exhaust during and after showering, and regularly cleaning bathroom tiles.

If you notice mould forming, contact your landlord or real estate agent for advice and document all correspondence between you on the matter.

Does bleach remove mould?

Bleach does not kill mould – it just removes the colour from the mould, so it’s invisible to the naked eye. But the mould will remain there, growing and posing a health hazard. Instead, reach for baking soda and white vinegar or a methylated spirits solution to kill your mould. Both these ingredients ‘explode’ the microscopic structure of the mould, immediately killing it.

Make sure to spot test on any new surface before cleaning. Be aware that vinegar is highly acidic and can damage surfaces like grout over time. Methylated spirits are generally safe to use on hard surfaces like grout, glass, stone, ceramic, marble, chrome, et cetera – plus they are biodegradable and eco-friendly.


woman displaying natural cleaning ingredients like white vinegar, baking soda and tea tree oil

Natural ingredients like white vinegar and baking soda kill mould much more effectively than bleach. Image: Matt Harvey

How to deal with mould after flooding

Floods and storms can result in pooled water sitting in and around your house for extended periods of time. This creates perfect conditions for mould to grow, especially considering that floodwater is generally full of bacteria. The Victorian Department of Health reports that high mould levels are likely if a house is flooded for more than two days.

If you return home after a flood and notice water damage, visible mould or a strong musty smell, quickly clean up and dry out your home to minimise mould. Ask your insurance company to advise you on their mould policy before you start, to make sure you don’t void any coverage you’re entitled to, and take photos, videos and notes before you start the clean-up.

You can help minimise mould after flooding by:

  • Opening all doors and windows to naturally air out the house

  • Removing any pooled water from inside and around the house

  • Moving any wet or flood-damaged items (especially soft or absorbent materials like carpet, rugs, mattresses, bedding, clothing, wallpaper, and other objects that can’t be properly cleaned, sanitised and dried) in a shed or garage until your home insurance claim is processed

  • Removing wet plasterboard and insulation to allow your internal wall spaces to properly dry out

  • Cleaning, disinfecting and drying hard surfaces like floors, walls, benchtops, ceilings and wall studs

  • Using fans and dehumidifiers to completely dry out the house once safe power returns to the area.

It's recommended to hire professional cleaners rather than tackle mould-affected areas yourself if you have a weakened immune system, allergies, lung disease or severe asthma. If you’re cleaning up after flood damage, wear protective gear like rubber gumboots, rubber gloves, shower cap, protective overalls, and a P1 or P2 mask.

If you are not affected by flooding, consider donating to people affected by storms and flooding via a reputable charity like GIVIT. Find out other ways to help and give support after a natural disaster here.


Mould and your health

Since mould spores float through the air to land on surfaces and reproduce, it’s all too easy to accidentally ingest mould spores. 

The Victorian Department of Health reports that mould can cause respiratory infections, worsened asthma, worsened allergic reactions, wheezing, sneezing, coughing and nasal congestion. People with pre-existing medical conditions like severe asthma, lung diseases, weakened immune systems, or allergies are more susceptible to mould exposure.

If you’re concerned about mould and your health, you can seek medical advice and contact your local council.


RACV Trades can help get your home in order.
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