Where mould thrives: study reveals Australia's mouldiest cities
Australia’s unseasonably wet winter has created the perfect conditions for mould to thrive. Sydney has already had its wettest August in 27 years, and forecasters warn even more rain is on the way.
Weather patterns in both the Indian and Pacific oceans are driving the downpours, and experts say a La Niña could form in the months ahead, bringing an even wetter Spring. With more damp days ahead, several regions are most at risk of mould, and Airtasker has unveiled where they are, which can officially be crowned Australia’s mouldiest.
To find out, we analysed several key factors, including the number of tasks posted on Airtasker for mould removal experts and Google searches for mould-related queries, as well as climate conditions and housing risk.
The mouldiest regions in Australia
Sydney’s Eastern Suburbs took the top spot as Australia’s mouldiest area, scoring 61.32 out of 100 on the mould index. The region ranked first for mould removal tasks, with the maximum task score of 100, an immense 547% above the national average. It also scored high for rainfall, averaging 4.2mm a day, and landed in the middle of the board for other contributing factors.
Close behind was the tropical city of Cairns, with an index score of 60.67. The warm, humid climate and heavy rainfall gave it the highest climate risk score in the country, pushing it up the rankings.
Five Sydney regions made the top 10 overall. While they face only moderate climate risk compared to tropical areas, they recorded strong search interest in mould removal and a high volume of Airtasker listings for mould-related jobs.
The least mouldy regions in Australia
Western Australia’s Outback took the crown as Australia’s least mouldy region, scoring just 9.15 out of 100. Its dry, arid climate keeps mould growth at bay, reflected in the low number of mould-related tasks and searches. Lower population density also means fewer properties at risk and fewer mould removal jobs being posted.
The bottom 10 were dominated by outback and remote regions in the warmer, drier, and less populated parts of the country, including Queensland and South Australia’s outback.
But it wasn’t all remote areas. A few Perth regions – North West, South West, and Inner Perth – also made the list. Across the state, low structural vulnerability and moderate-to-low climate risk went hand-in-hand with low searches for mould-related queries and tasks posted on Airtasker.
The mouldiest capital cities in Australia
With five Sydney regions appearing in the national top 10, it’s no surprise Sydney ranks as the mouldiest capital city in Australia. Over the past five years, the city has recorded almost 120% more mould removal tasks than the national average on Airtasker, and the highest volume of mould-related Google searches per 100,000 population. Its climate, combined with a high proportion of older homes with major cracks, contributes to a mould score of 92.48 out of 100.
Darwin comes in as the second most mouldy capital, with a score of 82.41. While the Darwin SA4 region narrowly missed the national top 10, the city’s high temperatures, heavy rainfall, and one of the highest rates of dwellings with major cracks give it a significant climate and structural risk.
The mouldiest regions by state
New South Wales
Sydney areas dominate the mouldiest parts of New South Wales, with six of the top 10 mouldiest spots. The Eastern Suburbs take out the top spot as the state’s worst-affected region. At a suburb level, Randwick records the highest share of mould-removal tasks on Airtasker (11%), closely followed by Bondi Beach (10%).
Richmond-Tweed in Northern NSW breaks up the Sydney stronghold in fourth place, driven by high search interest for mould removal as well as higher humidity, temperature, and rainfall compared to many other NSW regions.
Tweed Heads and Byron Bay are the suburbs experiencing the most mould in the region, based on Airtasker data.
Other areas to watch out for if you’re concerned about mould include Coffs Harbour, the Mid North Coast, Newcastle, and Lake Macquarie.
Victoria
Victorian regions score relatively low on the mould index overall, with the highest being Outer East Melbourne at 42.66, placing 36th nationally.
At a suburb level, Bayswater accounts for nearly 10% of mould-removal requests on Airtasker in the region, followed by Ringwood at 8%.
This area has a higher climate risk than many other Victorian regions, thanks to its higher humidity, lower temperatures, and greater rainfall.
A similar trend is seen in Melbourne’s South East, which comes in second for the state. In third place, and the first region outside Melbourne, is Warrnambool and South West Victoria, driven mainly by high search interest for mould-related issues.
Queensland
Queensland is home to some of the most mould-prone regions in Australia, with Cairns named the most mould-prone region in the state, with an index score of 60.67. Its warm, humid climate and high rainfall give it the country’s highest climate risk score for mould. Cairns City records the highest share of mould-removal tasks on Airtasker, with more than one in five jobs coming from the area.
The Sunshine Coast follows in second place with a score of 51.91, driven by similar tropical conditions and strong mould indicators. On the Sunshine Coast, Buderim tops the list for mould-removal tasks on Airtasker (11%), followed by Maroochydore (6%). In third place is the Gold Coast, scoring 51.71, where consistently high humidity and above-average rainfall contribute to its ranking.
Brisbane’s eastern suburbs, inner city, and several surrounding regions also appear in Queensland’s top 10, showing that mould risk is spread across both coastal and urban areas.
Western Australia
Western Australia may dominate the list of Australia’s least mouldy regions, but which parts of the state face the highest risk? While mould isn’t a major issue overall, Bunbury ranks as WA’s most at-risk area. This is largely due to its higher climate risk score, with above-average humidity and rainfall compared to the rest of the state. Bunbury also recorded a high level of Google search interest for mould-related queries, with 311.3 searches per 100,000 residents.
South Australia
Compared to the rest of the country, South Australia faces very little risk of mould. Even its mouldiest region – Adelaide Central and Hills – only ranks 47th nationally. It tops the state due to a higher climate risk score and stronger mould response indicators than other SA regions, but these figures are still low when compared to the more mould-prone states. Within the region, Fitzroy stands out as the most mould-prone suburb, with one in five Airtasker mould-removal tasks posted there.
How Australia's mould problem has changed over time
How to remove and prevent mould from the home
Tackle mould the right way
For small patches, supermarket mould sprays and a dry cloth can usually take care of mould on walls and corners. But for larger infestations, or when mould appears on porous materials like couches, mattresses or other furniture, it’s best to call in a professional. Different surfaces require different treatments, and a professional can ensure the mould is removed properly while preventing it from returning. This is important because, if not effectively treated, mould can release spores that may lead to health issues when inhaled — ranging from allergies and respiratory problems to neurological symptoms such as headaches and brain fog.
Keep humidity under control
Mould thrives in warm, damp environments, so keeping humidity under control is key. Ideally, indoor humidity should sit between 50% and 60% – but it must stay below 70%, as levels above can cause mould to grow rapidly. To reduce humidity in the home, simple steps like installing a dehumidifier, fixing leaks promptly, drying clothes outside, using air conditioning, and improving airflow can make a big difference.
Improve ventilation - especially in bathrooms
Bathrooms are the number one hotspot for mould, so proper ventilation is key. Ceiling vents work best, especially when placed directly above the shower, as wall vents often don’t remove moisture effectively. Around the house, keep windows and curtains open where possible to let in fresh air and sunlight – closed curtains and poor airflow can create the dark, damp conditions mould loves.
Find a Tasker to banish mould from your home
If mould has taken hold and you’re not sure how to get rid of it – or stop it coming back – post a task on Airtasker today and let an expert take care of it.
How much does mould removal cost?
The cost of mould removal largely depends on the size of the affected area. On Airtasker, the average mould removal task comes in at around $275, though prices can vary based on the type of mould, the extent of the infestation, and how tricky it is to reach.
While cleaning mould yourself might seem cheaper at first, professionals use special cleaning equipment and treatments that actually save you money by stopping damage to your home and keeping health problems from coming back.
In Australia, mould and mildew removal costs can range from $20 to $30 per hour. However, the price varies depending on the type of mould in your home, the size, and the difficulty of accessing the mould. Consider the factors and average service costs in this guide to prepare your budget effectively.
Want to know more about the cost of mould removal? You can view our full guide here.
| Mould removal service | Price guide |
|---|---|
| Small spaces | $50 – $100 |
| Kitchens / bathrooms | $50 – $4,000 |
| Crawlspaces | $500 – $4,000 |
| Entire house | $500 – $6,000 |
| Mould inspection | $150 – $350 |
| Air sampling | $250 – $300 |
| Half the house | $350 – $3,000 |
| Carpet cleaning | $35 per hour |
About the data
We conducted research using a combination of primary and secondary data to assess the mouldiest cities in Australia. Leveraging the latest available data for six metrics across three key categories, we looked at factors that indicate potential risks and indicators for regions signalling a high propensity for mould growth in Australian homes.
Using the metrics, we normalised the raw values and then weighted each, as listed below, to create an index score for comparability that allowed us to rank the mouldiest cities in Australia.
Please note that the use of the term city within this research is used interchangeably about SA4 regions, while capital cities are in reference to Greater Capital City Statistical Areas (GCCSA) as allocated by the Australian Bureau of Statistics.
- Climate Risk (60%) – evaluates the risk level for mould due to climate factors, with higher values signifying a greater risk
- Humidity (30%): mean daily relative humidity (%), using an average from relative humidity at max and min temperatures
- Temperature (10%): average daily temperature (°C), using an average from max and min temperatures
- Rainfall (20%): average daily rainfall (mm)
- Response Indicators (30%)– captures the real-world response to mould issues
- City Task Score (20%): rating the volume of mould removal tasks by city on the Airtasker platform out of 100, based on the maximum number of tasks per capita.
- Search volume per reach (10%): Google search volume for mould removal keywords and search terms per 100,00 reach
- Structural Vulnerability (10%)* – assesses the level of structural vulnerability to mould growth
- Housing conditions: proportion (%) of dwellings with major cracks in walls and floors
*note that this data is available only at the state level
Climate Risk: Climate Data was sourced from the SILO Australian climate database from 2020-2024. The average daily rainfall, average daily temperatures and average daily relative humidity were calculated by aggregating gridded data overlaying SA4 or GCCSA regional geographic shapefiles provided by the ABS to accurately correspond climate data to each region.
From this, a mould climate risk index was created from min-max normalised values of temperature, rainfall and relative humidity for each SA4 or GCCSA region to assess its level of mould risk, with the following values as reference points:
Variable | Min (low risk) | Max (high risk) |
Temperature | 10°C | 25°C |
Relative Humidity | 60% | 80% |
Rainfall | 1mm | 6mm |
Response Indicators: Internal Airtasker data was utilised by looking over 40,000 tasks posted on the Airtasker platform that were related to mould removal between January 2020 and July 2025 inclusive. The city task score was calculated based on ABS population data and the calculated total persons for the given time period, matching the internal task data to generate a city task score.
The municipality geographic level was used as a proxy to determine regional Google search volume via keyword ad planner at the SA4 level. Search data was compiled from July 2021 – June 2025, inclusive. Each SA4 region was allocated the nearest municipality for its average monthly search volume per 100,000 reach based on each of its coordinates. In instances where the municipality allocated had a limited search volume reach, the nearest city was used to calculate the search volume per reach metric.
Structural Vulnerability: Data for structural vulnerability was sourced from the ABS Housing Mobility and Conditions data from 2019-20, where a percentage of dwellings with major cracks in walls and floors is used to highlight potential for moisture intake. Households in SA1s regions defined as “very remote” were excluded in the percentage estimates of dwellings with Major cracks in walls or floors, which accounts for about 21% of the population of Northern Territory.
Sources:
- SILO Australian climate database, 2020-2024
- Australian Bureau of Statistics: Estimated Regional Population, 2020-24
- Australian Bureau of Statistics: Housing Mobility and Conditions, 2019/20
- Google Keyword Ad Planner: Search Volume from July, 2021 – June 2025
- Airtasker internal task data, 2020-2025