Which Australian homes get the most mould: by type, tenure and age

In Australia, rental and social-housing homes report much more mould than owner-occupied ones. Around 13% of owners report mould, versus 19 to 33% of private renters and up to 42 to 50% in social housing (Coulburn and Miller 2022). Overall, 35% of 22,550 households in the 2022 Australian Housing Conditions Dataset reported mould, most often in older, poorly ventilated homes.

By Ben Knight, founder of Aurala Naturals. Last updated July 2026.

Which Australian homes report the most mould?

Rentals and social housing report it most, owner-occupiers least. The table below pulls the tenure and dataset splits into one place. Read every figure as self-reported, which means a household ticked a box to say they had mould, not that an inspector measured it.

Home category or tenure Share reporting mould Sample or dataset Source and year How to read it
Owner-occupied Around 13% Reviewed Australian studies Coulburn and Miller 2022 Lowest-reporting group
Private rental 19 to 33% Reviewed Australian studies Coulburn and Miller 2022 Range across several studies of different size and method
Social housing As high as 42 to 50% Reviewed Australian studies Coulburn and Miller 2022 Highest reported; older and smaller studies, read as an upper band
All homes 35% 22,550 households AHURI / Baker et al. 2022 Self-reported; second most common building problem
Rental bathrooms 18% 1,019 private renters ACOSS-UNSW 2025 Bathroom-specific, 2025 survey
National baseline 17.97% 14,456 homes ABS 1994, via review The last true national figure

35% of renters in the reviewed studies said they had experienced mould in the bathroom, and 20% in the bedroom (Coulburn and Miller 2022). A separate 2025 survey put the share of rental bathrooms with mould at 18% (ACOSS-UNSW). Those two measure slightly different things. One asks renters about their experience, the other counts affected bathrooms, so they sit side by side rather than one replacing the other.

Are rental homes more likely to have mould than owner-occupied homes?

Yes. Around 13% of owner-occupiers report mould, against 19 to 33% of private renters (Coulburn and Miller 2022). The gap is not really about the tenant. It tracks maintenance. Rental homes carry more structural defects than owner-occupied ones, which a University of Melbourne analysis links to poorer upkeep and unrepaired leaks (University of Melbourne, 2023). Water-related defects, the main cause of mould, cost about A$7,000 more to repair than other faults, so they are exactly the kind of job that gets deferred.

The 2025 ACOSS-UNSW survey shows the mechanism plainly. Among 1,019 private renters, 24% had leaks or flooding, 31% had pests and 21% had hot-water problems. In the same survey, 74% had hit some defect or issue and half said their home needed repairs, with roughly one in ten needing urgent repairs (ACOSS-UNSW 2025).

Is mould worse in social housing or private rentals?

On the numbers reviewed, social housing reports the most. Coulburn and Miller put owner-occupiers near 13%, private rentals at 19 to 33% and social housing as high as 42 to 50%. Here is the honest caveat: the social-housing figures come from older and smaller studies, so treat 42 to 50% as an upper band, not a settled national rate. One Victorian rental inspection found 19% of properties had visible and extensive mould, most of it in the bathroom, and one study found up to 78% of the rental properties surveyed had poor-quality conditions overall (Coulburn and Miller 2022).

Do apartments or houses get more mould?

It depends more on ventilation than on the building type itself. Apartments and flats are more likely to lack mechanical bathroom ventilation, while houses are more likely to have an exhaust fan, though some vent back into the roof space rather than outside. Either way, shower moisture that cannot escape ends up as condensation on cold surfaces, and that is where mould starts. The table below sets out the main dwelling and age risk drivers.

Risk driver Tends to carry more risk Tends to carry less risk Why it matters for mould
Bathroom ventilation Apartments and flats, more likely to lack mechanical bathroom ventilation Homes with an exhaust fan vented outside Trapped shower moisture feeds condensation on cold surfaces
Building age Older stock with age-related defects, and newer builds with condensation or build defects Well-built, well-maintained stock of any age Mould is not confined to old homes; the risk cuts both ways
Maintenance and tenure Rentals with unrepaired leaks Better-maintained owner-occupied homes About half of mould-causing defects are water-related
Energy performance The 70% of existing houses rated three stars or lower Higher-rated, better-sealed and ventilated homes Poor thermal performance drives condensation and damp

Does a home's age decide its mould risk?

Mostly, no. Age cuts both ways. Older stock carries age-related defects and worn seals. Newer builds bring their own problem: tighter construction that traps moisture, plus surface and interstitial condensation and build defects (Coulburn and Miller 2022). Poor thermal performance is part of it. About 70% of existing Australian houses hold an energy rating of three stars or lower, which AHURI links to condensation and damp (AHURI). So a five-year-old apartment and a fifty-year-old cottage can both be mould-prone, for opposite reasons.

What percentage of Australian homes have mould?

The best current figure is 35%, self-reported across the 22,550 households in the 2022 Australian Housing Conditions Dataset (AHURI, Baker et al.). That made mould the second most common building problem, behind cracks in walls or floors at 44% and ahead of plumbing at 27%. Seven in ten of those homes had at least one building-quality problem.

Here is the caveat nobody puts on the headline. Australia has not properly measured national mould prevalence since 1994, when an ABS survey of 14,456 homes found 17.97% had mould or mildew. The 2022 review that gathered this evidence located just 45 Australian studies and concluded national prevalence and geographic spread are essentially unknown (Coulburn and Miller 2022). So 35% is the best recent self-reported number, not a measured national rate.

What does it cost to put mould-related defects right?

These are property costs, and they climb fast once moisture reaches materials. Indicative 2026 ranges from an industry cost guide:

Scope of work Indicative cost, A$ (2026)
Bathroom or single small room $500 to $3,000
Moderate single room $3,000 to $8,000
Multiple rooms or structural involvement $8,000 to $20,000
Whole-house or HVAC-contaminated $15,000 to $30,000+

Those are contractor guide ranges (Disaster Recovery Australia), not official figures, so read them as ballpark. The bigger money sits upstream. Water-related defects, the main cause of mould, cost about A$7,000 more to repair than other defect types, and about half of the defects that caused mould were water-related (University of Melbourne / Victoria University analysis). Fix the water, or the mould keeps coming back.

What does this mean for renters and owners?

We built this page because renters kept asking us one plain thing: is it just my place, or is this normal. The data says it is not just you. If you rent, mould is far more common in your tenure than in owner-occupied homes, and the driver is usually an unrepaired moisture problem rather than anything you did. In New South Wales, NSW Fair Trading states that where mould develops because a landlord failed to repair a defect or the property lacked adequate ventilation, "the landlord is responsible and must fix the problem" (NSW Government).

For owners, the take-home is that age alone tells you little. Ventilation, maintenance and how well the home sheds moisture matter more. Whichever side you are on, the pattern in every dataset points the same way. Mould follows damp, and damp follows the buildings that are hardest to keep dry.

Methodology and sources

Every figure on this page is self-reported survey or review data unless noted, and each number is attributed to its source. We have added nothing of our own.

Figures are drawn from studies of differing size, method and year. Tenure ranges are reported across several studies rather than measured in one, and social-housing figures come from older, smaller samples, so read them as ranges. National prevalence has not been measured since 1994.

Free to cite with attribution to Aurala Naturals. If you use these figures, please link back to this page so readers can check the sources for themselves.

Published by Aurala Naturals, an Australian brand making natural mould-spore air products for the home. This page is descriptive housing data, not medical or professional advice.

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