The 2026 Australian Renter Mould Index
The 2026 Australian Renter Mould Index. Published by Aurala Naturals. Compiled by Ben, founder, from Bureau of Meteorology, government tenancy, and peer-reviewed sources. Last updated July 2026.
About one in three Australian homes reports mould, and renters carry more of it than owners. Using Bureau of Meteorology humidity and rainfall data, this index ranks the eight capital cities by how damp they are, the single biggest driver of household mould. Darwin and Sydney sit at the top. Adelaide sits at the bottom.
Mould needs moisture. The damper the air and the more often surfaces get wet, the harder mould is to keep out, especially in a rental you cannot renovate. We pulled the Bureau of Meteorology's own station humidity and rainfall figures for every capital, combined them into a single Damp Risk Score, and cross-checked them against the national mould data and the rental rules in each state. Every number below is linked to its source.
The 2026 Renter Mould Index: Australian capitals ranked by damp risk
Damp Risk Score is a 0 to 100 scale built from three Bureau of Meteorology measures: mean relative humidity (the average of the 9am and 3pm readings), mean annual rainfall, and the mean number of rain days a year. Higher means damper, and damper means a harder mould problem to hold back.
| Rank | Capital | Humidity 9am | Humidity 3pm | Rainfall (mm/yr) | Rain days/yr | Damp Risk Score |
|---|---|---|---|---|---|---|
| 1 | Darwin | 71% | 54% | 1,737 | 94 | 91 |
| 2 | Sydney | 69% | 57% | 1,211 | 100 | 86 |
| 3 | Melbourne | 69% | 53% | 648 | 100 | 63 |
| 4 | Brisbane | 65% | 58% | 1,031 | 85 | 60 |
| 5 | Hobart | 68% | 58% | 611 | 87 | 58 |
| 6 | Perth | 65% | 48% | 755 | 85 | 29 |
| 7 | Canberra | 72% | 47% | 616 | 72 | 25 |
| 8 | Adelaide | 62% | 47% | 541 | 82 | 11 |
Two things worth calling out. Canberra has the highest 9am humidity of any capital, 72%, but it drops to 47% by mid-afternoon. That morning figure is a cold inland fog reading, not a sign of a damp home, which is why we average the two times of day and Canberra lands near the bottom. And the genuinely humid part of the country is the tropical north. As a reference point outside the capitals, Cairns runs 72% humidity at 9am, 62% at 3pm, and 2,026mm of rain across 120 rain days a year, the dampest place we measured. The Bureau's own climate maps state that relative humidity is highest in northern Australia and along the coasts.
How common is mould in Australian homes?
Mould is not a fringe problem. The figures below are the most recent national data available.
- 35% of Australian homes report mould, second only to wall cracks among building-quality problems, from the 22,550-household Australian Housing Conditions Dataset (AHURI, drawn from Baker et al., 2022, Scientific Data).
- 50% of Australians had mould or dampness in their home in the last 12 months, and one third (34%) reported mould specifically, from a nationally representative survey of 5,041 people (Asthma Australia, 2022).
- A 1994 Australian Bureau of Statistics national survey put the figure at almost 18%, the last time the ABS measured it nationally, reported in the peer-reviewed review by Coulburn and Miller (2022). No comparable national survey has been run since.
Renters get more mould than owners
The same peer-reviewed review found reported mould is far higher in rentals than in owner-occupied homes.
| Housing type | Reported mould |
|---|---|
| Social housing | 42 to 50% |
| Private rental | 19 to 33% |
| Owner-occupied | 13% |
Recent renter-specific data backs this up. A 2025 ACOSS and UNSW Sydney survey found 18% of rental bathrooms have mould and 24% of rental homes have leaks or flooding, with half of renters living somewhere that needs repairs (UNSW Sydney). An earlier CHOICE, National Shelter and tenants' organisation survey found 20% of renters had experienced leaking, flooding and mould (Tenants' Union of NSW).
Which states protect renters from mould?
Whether your landlord has to deal with mould depends on which state you rent in. Four states now name mould directly in their rental minimum standards. Two do not, or barely.
| State or territory | Mould in the minimum standard? | Who is responsible? |
|---|---|---|
| Victoria | Yes. Every room must be free from mould and damp, with adequate ventilation. | Landlord for structural or ventilation causes; tenant for tenant-caused. |
| New South Wales | Yes. Adequate ventilation is one of seven minimum standards. | Landlord for building or ventilation defects; tenant only where the tenant caused it. |
| Queensland | Yes. Premises must be weatherproof, structurally sound, and free from damp. | Landlord for building or ventilation causes; tenant for tenant-caused. |
| South Australia | Yes. Prescribed standards require rooms free from damp and mould. | Landlord for structural or ventilation causes. |
| Tasmania | Partial. Premises must be clear of mould, weatherproof and not significantly damp. | Landlord for habitability; tenant for tenant-caused. |
| Western Australia | Responsibility rules only. Tenant liable only for tenant-caused mould, and the landlord cannot charge the tenant for building-caused mould. | Landlord for building causes; tenant only for tenant-caused. |
| ACT | Minimal. The only enacted numeric minimum standard is ceiling insulation; mould sits under the general habitability duty. | Landlord under the fit-for-habitation duty. |
| Northern Territory | No prescribed mould schedule. Handled under the general habitability and repair duty. | Landlord under the habitability and repair duty. |
Standards on paper are not the same as homes that pass them. A La Trobe Business School study of Victorian rental audit data found just 39.91% of 1,723 homes audited in early 2024 met the minimum standards, with mould and damp among the persistent failures (La Trobe University, published in the journal Cities). Mould is also expensive to leave: mould defects cost around A$7,000 more to remediate than other rental repairs (Victoria University, via The Conversation).
What renters can actually do about it
Most renters cannot re-plumb a bathroom or re-glaze a window. The levers that are in your control are moisture and airflow. Run the exhaust fan during and after every shower, and for a while afterwards, not just while you are in there. Wipe down wet surfaces and shower screens. Keep furniture a small distance off external walls so air can move behind it. Open up on dry days, and use the driest air you can get into the room. If mould keeps returning in the same damp spot, that spot is the pattern, not a one-off clean. For a simple summary of why mould keeps coming back after you clean it, see how mould works.
Methodology and sources
Damp Risk Score is built from three Bureau of Meteorology measures for each capital's long-record climate station: mean relative humidity (the average of the 9am and 3pm annual figures), mean annual rainfall, and mean annual rain days. Each measure is scaled 0 to 100 across the eight capitals, then combined with humidity weighted 40% and rainfall and rain days weighted 30% each, because surface humidity is the direct driver of mould while rainfall and rain-day frequency supply the moisture. Averaging the two humidity readings deliberately corrects for cold-morning-fog stations like Canberra that read high at 9am but dry out by afternoon.
Caveats, stated plainly. The Bureau's all-years humidity tables end in 2010, though rainfall records run to 2026, and station record lengths vary. This is a climate-exposure index, not a measurement of mould in any individual home, and local factors like ventilation, building age and leaks matter as much as the weather outside. The national prevalence figures come from surveys of different designs and years, and the strongest ABS point estimate is from 1994.
Sources: Bureau of Meteorology climate statistics for Australian locations (per-station humidity, rainfall and rain-day tables); AHURI and Baker et al. 2022 (Scientific Data); Asthma Australia 2022 national mould and dampness survey; Coulburn and Miller 2022 (International Journal of Environmental Research and Public Health); ACOSS and UNSW Sydney 2025; CHOICE, National Shelter and the Tenants' Union of NSW; Consumer Affairs Victoria, NSW Government, Queensland Residential Tenancies Authority, Consumer Protection WA, and the ACT Government; La Trobe Business School (journal Cities); Victoria University via The Conversation.
Related resources
- Renter mould rights in Australia: a state-by-state guide
- The Australian mould season calendar: when mould is worst by city and month
- Which Australian homes get the most mould: by type, tenure and age
Free to cite with attribution to the Aurala Naturals Renter Mould Index, 2026. Aurala Naturals makes First Light, a natural mould-defence blend made in Australia.