The State of Mould in Australian Rentals 2026

35% of Australian homes report mould. In owner-occupied homes the rate is 13%. In private rentals it runs as high as 33%, and in social housing as high as 50%.

The State of Mould in Australian Rentals 2026 gathers the strongest available Australian evidence in one place. It is a mould-only picture: how common mould is in rented homes, how renters compare with owners and social housing tenants, how unevenly the law protects them from one state to the next, and what it costs when mould is left to spread. Every figure below is drawn from a named study or dataset and linked to its primary source. Health effects are out of scope: this is a housing-conditions report.

How many rentals have mould

The most robust national benchmark comes from the Australian Housing Conditions Dataset, a survey of 22,550 households led by Professor Emma Baker. It found that 35% of Australian homes report mould, making mould the second most common building-quality problem after cracked walls. A separate national survey the same year put the figure at 34%.

Rental-specific data is starker. In the 2025 "Rights at risk" study of 1,019 private renters by ACOSS and UNSW Sydney, 18% of rental bathrooms had visible mould and 24% of rentals had experienced leaks or flooding. On Aurala's Renter Mould Index, which ranks the capitals on Bureau of Meteorology data, Darwin is the dampest capital and Sydney the second, while Adelaide is the driest and Cairns the most humid, so where a rental sits matters as much as how it is built.

Renters versus owners versus social housing

An Australian integrative review by Coulburn and Miller (2022) pulled together 45 studies and found a clear tenure gradient. Owner-occupiers reported the least mould, private renters more, and social housing tenants the most.

For the full breakdown by home type and building age, see mould risk by home type and age.

The rights gap by state

Australia has no single national rule on mould in rentals, so protection depends on the postcode. Three states name mould directly in their rental minimum standards: Victoria, where the standards require a home to be free of mould and damp caused by the building structure; South Australia, where mould is the landlord's responsibility under the minimum housing standards that took effect on 1 July 2024; and Queensland, whose minimum housing standards (from 1 September 2023) require a home to be free from vermin, damp and mould. New South Wales addresses it more indirectly, through fit-for-habitation rules on ventilation and significant dampness.

Naming mould is not the same as fixing it. In Victoria, where mould is named, compliance still fell sharply: of 1,723 rentals audited in the first five months of 2024, only 39.91% met the minimum standards, down from 76% in 2021, and mould and damp was the single most common failure. See the full state-by-state comparison in renter mould rights in Australia.

What it costs

Mould is expensive to leave. A Victoria University study found that about half of the defects causing mould are water-related, and that water-related defects cost on average A$7,000 more to fix than other defects. The longer they sit, the further the damage spreads. A full breakdown of remediation and replacement costs is set out in the cost of mould in Australian homes.

The larger cost is the one that never gets billed, because the repair is never requested. In the ACOSS and UNSW "Rights at risk" study, half of renters (50%) live in a home that needs repairs and one in ten need urgent repairs, yet 68% worry that asking for a repair would trigger a rent increase, 56% fear eviction, and 52% fear being placed on a blacklist. Mould that is not reported is mould that keeps growing, which is one reason renters carry more of it.

Why rentals get it worse

• More structural defects. Rental stock has more building defects than owner-occupied stock, and water-related defects are the leading cause of mould.
• Renters cannot fix the building. Tenants can wipe a surface, but they cannot re-waterproof a bathroom, improve subfloor ventilation, or replace a leaking roof.
• Under-reporting. With 68% of renters worried that a repair request will raise their rent, problems are hidden rather than fixed.
• The worst homes are the cheapest. Compliance is lowest at the affordable end: in the La Trobe audit, some disadvantaged suburbs recorded pass rates as low as 22.84%.
• Older stock, wetter climates. Age and local humidity compound the problem, and renters are concentrated in exactly the homes and cities where both run highest.

Methodology and sources

This report consolidates published Australian studies, government datasets and state rental legislation current to 2026. Figures are prevalence or self-report where the underlying study is a survey, and are given as ranges where studies disagree. The 35% and 34% national figures come from two separate 2022 surveys. Tenure figures (13%, 19% to 33%, 42% to 50%) come from a 2022 integrative review of 45 studies; the social housing upper band is drawn from older and smaller studies and is reported as a range for that reason. No health, medical or product claims are made. Journalists and editors can find a media summary and citation guidance on our press page. Every figure above links to its named source.