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Source: The Conversation (Au and NZ) – By Rebecca Bentley, Professor of Social Epidemiology and Director of the Centre of Research Excellence in Healthy Housing at the Melbourne School of Population and Global Health, The University of Melbourne


Rental properties are more likely be mouldy than other homes. This is a concern as excessive mould growth is known to harm human health.

Once buildings are infested with mould, the difficult and costly issue of remediation arises. Landlords and tenants are caught in the middle of a tussle over who is responsible for fixing the problem. As one Melbourne renter and research participant told our colleague Maria Gatto, during a study validating mould reporting:

The landlord came around [and] walked [into] every room where there’s black mould on the ceiling – like it’s freaking [something out of the TV series] Stranger Things – and she’s like, ‘Oh, a little bit of mould in winter, it’s very normal, it’s fine […] this happens every winter, it’s not a big deal’.

Heading into winter, after three consecutive La Niñas, conditions are ripe for a mega mould season. Combining our expertise in health, law, building and construction, we examine the problem of mould in homes and offer guidance for both renters and landlords.

Read more:
Sudden mould outbreak after all this rain? You’re not alone – but you are at risk

Ideal conditions for growth

Mould is a fungal growth that reproduces via tiny airborne particles called spores. When these spores settle on moist, plant-based construction materials such as wood, wallpaper or plasterboard, they can form a new colony.

Growth is more likely when homes are cold, humid, lack air flow, or suffer from water damage. Outbreaks have been reported in flooded parts of southeastern Australia.

Black mould an invisible threat growing behind walls of flood-affected homes (ABC News)

So why is the problem of household mould worse in rentals? Weak regulation of tenancy legislation is just one of many factors. Rental properties tend to be poorly maintained, with structural problems such as leaks. Given this, they can be expensive to heat.

A chart showing the percentage of homes with structural defects in each category
Rental homes have more structural defects than owner-occupied homes.
Nicola Willand, using data from Moore et. al., (2020), Warm, cool and energy-affordable housing policy solutions for low-income renters, AHURI Final Report, vol. no. 338. Appendix 2, Author provided

How mould makes people sick

The World Health Organization recognises mould can be harmful.

A 2022 Asthma Australia report revealed people living in mouldy homes were more likely to have asthma and allergies. A systematic review of peer-reviewed research found children living in mouldy homes were more likely to experience asthma, wheeze and allergic irritation of the eyes, nose, throat and mouth (allergic rhinitis).

Living with mould is a source of stress. People worry about the consequences for their health and there is a growing body of evidence describing the negative mental health effects of mouldy, damp homes.

Read more:
Thinking of buying a dehumidifier? Advice from an expert on mould and damp

Problems with managing mould in the rental sector

There is a gap between building and residential tenancies legislation. A building deemed to meet the minimum standards of the construction code with respect to mould may not meet the minimum standards for rental. That’s because there’s ambiguity in the National Construction Code around “minimum standards of health”.

For example the Victorian Building Act 1993 contains some provisions for the relevant surveyor to serve a notice on the basis of a health circumstance affecting a user. However, there is no guidance on how to assess the health of the indoor environment, or to deliver a building direction that will address the root cause for mould. This varies by state and territory.

Mould remediation can be costly. A study by Victoria University found half the defects causing mould were water-related. These were more expensive to fix than other problems, by an average of A$7,000.

Each winter, Tenants Victoria deals with a spike in renters seeking legal help to resolve their mould problems. This led to the service launching an annual winter Mould Clinic in 2021.

Despite increased legal protections, renters are still struggling to get mould fixed. For these reasons, many renters find the legal process doesn’t offer a solution to their problem, and instead move to a new property, with all its attendant costs and stresses. Others can’t afford to leave, or live in social housing with limited transfer options.

Charting mould in homes across Australia

A bar chart comparing the prevalence of mould in homes across Australian states and territories
Mould is more prevalent in rentals compared to owner-occupied dwellings. Mould is most commonly reported in New South Wales. The difference between owners and renters is greatest in the ACT.
Australian Housing Conditions Dataset 2022 doi:10.26193/SLCU9J, Author provided

Where does the responsibility lie?

Tenancy legislation varies by state and territory. Renters should familiarise themselves with the regulations in their jurisdiction.

In Victoria, residential tenancies legislation has set the criteria that “each room in the rented premises must be free from mould and damp caused by or related to the building structure”. Landlords now must disclose if they have treated mould in the past three years.

Similarly, new legislation in Queensland (coming into effect in September) states rental properties should be free from vermin, damp and mould where this is caused by issues with the structural soundness of the property.

In New South Wales, the landlord needs to disclose signs of mould and dampness in the condition report (but not necessarily have fixed it). Mould is not mentioned in the ACT residential tenancies legislation.

For the most part, the responsibility for mould in rental properties lies with landlords if the cause is structural –- for example, if a broken or faulty window frame has let rainwater inside.

Requests for urgent repairs can be accompanied by an assessment report by an occupational hygienist, environmental health professional or expert from the local council. People with an existing health condition such as asthma can include a doctor’s report.

What next?

To achieve change across all relevant domains of regulation, construction, natural disaster response and government policy, we need a sustainable, broad healthy housing agenda in Australia. We also need to consider options for immediate action.

As one Victorian renter noted:

When we buy a car for the purpose of driving on the roads, we’re required to get a roadworthy certificate to make sure it’s safe, because of the risk to other people […] Ideally it would be great if there was [some] kind of ‘rentworthy’ certificate […] to demonstrate that the property has been inspected, to identify any structural issues that might affect the tenant’s health and wellbeing. And that that be available to tenants […] before they enter into a lease or before (the property is) even able to be advertised.

Read more:
Mould and damp health costs are about 3 times those of sugary drinks. We need a healthy housing agenda

For those in Melbourne, a free Tenants Victoria event on this topic will be held at RMIT University Storey Hall on Wednesday, May 17 at 1pm. It will be followed by a free pop-up legal clinic.

Quotes in this article were collected by Maria Gatto as part of her Masters of Public Health, conducted at the Melbourne School of Population and Global Health in 2022.

The Conversation

Rebecca Bentley receives funding from the National Health and Medical Research Council and the Australian Research Council.

Nicola Willand receives or has received funding for research from various organisations, including the Australian Research Council, the Victorian State Government, the Lord Mayor’s Charitable Foundation, the Australian Housing and Urban Research Institute, the Future Fuels Collaborative Research Centre and the Australian National Health and Medical Research Centre. She is affiliated with the Australian Institute of Architects.

Tim Law receives or has received funding from the Victorian Building Authority, the National Health Medical and Research Council, the Australian Building Codes Board, Tasmania Consumer Building and Occupational Services, and Commercialisation Australia.

ref. Breaking the mould: why rental properties are more likely to be mouldy and what’s needed to stop people getting sick –