Australia’s Mould Problem Is Growing: Is Your Home at Risk?

Mould is a familiar problem in many Australian homes, but recent findings have put the issue back in the spotlight. Following an unusually wet winter, Airtasker reported a 12% increase in mould removal tasks over just three weeks (at the time of writing), suggesting more households are finding themselves dealing with unwanted mould.

But some parts of Australia appear to be more susceptible than others. An analysis looking at factors including mould removal jobs, Google search trends, humidity, rainfall, temperature and dwelling conditions ranked the areas considered most at risk—and Sydney’s Eastern Suburbs came out on top, earning the unexpected title of Australia’s “mould capital”.

Of course, you don't need to live in one of Australia's identified mould hotspots to experience a problem. Wherever there is persistent moisture, high humidity, condensation, poor ventilation or water damage, mould can find the conditions it needs to grow—and sometimes it may be developing before you even realise it's there.

So, what can these latest findings tell us about the mould risk in our own homes? In this guide, we'll look at where Australia's mould hotspots are, why certain homes may be more susceptible, where mould can hide and what you can do to treat existing mould and help prevent it from returning.

Sydney’s Eastern Suburbs have been named Australia’s “Mould Capital”

Sydney’s Eastern Suburbs may be known for their beaches, harbour views and some of the country’s most sought-after properties, but recent data has highlighted a less desirable characteristic: mould risk.

An analysis by Airtasker ranked Sydney’s Eastern Suburbs as Australia’s most mould-prone region, giving the area a reported “mouldiness score” of 61.32 out of 100. The ranking considered several factors, including mould removal jobs, Google search activity, humidity, rainfall, temperature and local dwelling conditions.

And it wasn’t the only part of Sydney to rank highly. Five Sydney regions appeared in the national top 10, alongside several areas of Queensland and Tasmania.

Source: Airtasker

Importantly, being named a mould hotspot doesn’t mean every property in these areas has a mould problem. The ranking is better viewed as an indication of where a combination of environmental conditions, housing factors and reported mould activity may make the issue more common.

It also raises an interesting question: why do areas as different as Sydney’s Eastern Suburbs, Cairns and Tasmania’s West and North West all appear on the same list? The answer comes down to more than location alone.

Why are some parts of Australia more prone to mould?

Looking at the mould hotspot rankings, there’s an interesting mix of locations. Sydney accounts for five of the top 10 regions, while warmer and more humid areas such as Cairns, the Sunshine Coast and Gold Coast also feature prominently.

So, why are some parts of Australia seemingly more prone to mould than others?

Mould thrives where there is moisture, and local climate can make it easier for that moisture to build up. Areas that experience high humidity, frequent rainfall or prolonged damp conditions may naturally provide a more favourable environment for mould growth.

But outdoor weather is only part of the picture. What happens inside the home matters too. Some of the most common factors that can contribute to mould include:

• High humidity – Moist air can create damp conditions, particularly when indoor humidity remains high for extended periods.

• Condensation – Moisture can collect on windows, walls and other cool surfaces, especially during colder weather.

• Poor ventilation – Bathrooms, laundries, kitchens and other moisture-producing areas can stay damp when there isn't enough airflow.

• Leaks and water damage – Leaking roofs, plumbing problems and water entering through walls or windows can leave building materials persistently damp.

• Limited airflow – Mould can develop in enclosed or poorly ventilated areas such as wardrobes, cupboards and behind large pieces of furniture.

• Building conditions – Insulation, drainage, ventilation and the overall condition of a property can influence how effectively moisture is managed.

This also helps explain why mould isn't exclusively a tropical or warm-weather problem. A humid Queensland home and a colder Tasmanian home may develop excess moisture for very different reasons. In cooler conditions, for example, warm indoor air meeting cold surfaces can create condensation, providing the moisture mould needs.

Read related article: Winter vs. Summer Mould: What’s the Difference

Ultimately, your postcode alone doesn't determine whether you'll have mould. Local weather can increase the risk, but the amount of moisture, ventilation and airflow within an individual property can make just as much difference.

And that means even if your area didn't appear among Australia's top mould hotspots, your home could still have the right conditions for mould to grow.

Where should you look for hidden mould?

Mould isn't always as obvious as a dark patch spreading across a wall or ceiling. Sometimes it can develop in damp, poorly ventilated or rarely disturbed areas, meaning a problem may be growing before you notice visible signs.

If your home has recently experienced heavy rain, a leak, water damage or persistent condensation, it's worth paying closer attention to areas where moisture can collect or take longer to dry.

Some common places to check include:

• Behind wardrobes and large furniture – Limited airflow between furniture and walls can allow moisture to linger.

• Inside cupboards and wardrobes – Enclosed spaces can trap humidity, particularly when they have little ventilation.

• Around windows and window frames – Regular condensation can leave frames, seals and surrounding surfaces damp.

• Bathrooms and shower areas – Check ceilings, grout, silicone seals, behind fixtures and other areas regularly exposed to moisture.

• Under sinks and around plumbing – Slow or unnoticed leaks can create persistent dampness inside cabinets.

• Ceilings and upper walls – Discolouration or damp patches may indicate a roof leak or another source of moisture.

• Laundries and kitchens – Steam, drying clothes and everyday water use can increase indoor moisture when ventilation is limited.

• Carpets and other porous materials – Areas affected by leaks, flooding or prolonged dampness may not always dry as quickly as they appear to.

• Around air conditioners and vents – Condensation and moisture can develop around air-conditioning components, so these areas are also worth checking.

Look beyond what you can see

Your eyes aren't your only tool for spotting a possible mould problem. A persistent musty or damp smell, recurring condensation, peeling or bubbling paint, water stains and damp patches can all indicate that excess moisture is present—even if you can't immediately see mould.

Pay particular attention if the same area keeps becoming damp or mould returns soon after you've cleaned it. That can be a sign that the underlying moisture problem hasn't been resolved.

Small mould patch or bigger problem? Know when DIY remediation may not be enough

Not every mould problem requires the same approach. Small, isolated patches of surface mould may be manageable at home, particularly when you can identify and address the source of the moisture. If you're tackling a smaller mould problem yourself, you can follow the practical steps in our Guide on How to Test, Clean & Prevent Mould Growth with SAN-AIR, which covers how to identify, treat and manage mould around the home. 

However, it may be time to seek professional help if the mould is widespread, keeps returning, has developed after significant water damage, or may be growing inside walls, ceilings or other difficult-to-access areas. Mould affecting porous materials or covering a large area can also require more specialised treatment.

The key is knowing when a mould problem has moved beyond a straightforward DIY job. If you're unsure who can help, read our guide Who to Call for Mould Problems: The Experts You Need for Every Type of Mould Issue for a breakdown of the different professionals and when you might need them.

Conclusion: Keeping mould under control at home

Whether or not your suburb appears on Australia’s list of mould hotspots, the conditions inside your home ultimately matter most. Mould can develop wherever excess moisture, dampness and poor ventilation create the right environment for it to grow.

Managing mould effectively also means looking beyond the patch you can see. Cleaning or treating existing mould is important, but if the underlying source of moisture remains, the problem may simply return.

A more complete approach involves four key steps:

Identify the problem → Control the moisture → Treat existing mould → Support ongoing mould management

This could mean fixing leaks, improving ventilation, managing condensation and humidity, treating mould-affected areas appropriately, and taking ongoing steps to help keep your indoor environment better protected.

Most importantly, keep an eye on areas where mould has appeared before. Regular checks can help you spot returning moisture or mould early, before a small problem has the chance to become a much bigger one.

Wherever you live in Australia, staying aware of the conditions that encourage mould—and dealing with them early—is one of the best ways to help keep your home cleaner, drier and better protected.

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