The question of who is responsible for mould in a rental property is one of the most contested issues in NSW tenancy law. In the Northern Rivers region, where subtropical humidity means almost every home will develop mould somewhere, sooner or later, landlords and tenants regularly find themselves at an impasse. The landlord says the tenant caused the mould through inadequate ventilation; the tenant says the house is inherently damp and the landlord isn’t maintaining it. Often, both parties have a point.
This guide sets out the NSW legal framework, explains how responsibility is typically allocated in different scenarios, and describes what both landlords and tenants can do when they face this dispute in a Northern Rivers context.
Quick answer (BLUF)
Under the Residential Tenancies Act 2010 (NSW), landlords must maintain rental properties in reasonable repair and ensure they are fit for habitation. Mould caused by building defects, structural moisture issues, or inadequate ventilation is the landlord’s responsibility. Mould caused by tenant behaviour, failing to use ventilation, lifestyle moisture generation, is generally the tenant’s responsibility. In practice, the Northern Rivers subtropical climate often creates situations where both factors contribute and the division of responsibility is genuinely contested.
The legal framework
Landlord’s obligations: Section 52 of the Residential Tenancies Act 2010 (NSW) requires landlords to provide and maintain premises in a reasonable state of repair. This obligation extends to ensuring the property is fit for habitation, which means addressing conditions that affect the health or safety of occupants. The NSW Fair Trading guidance on mould states clearly that mould arising from building defects, including inadequate ventilation systems, roof leaks, plumbing failures, and inadequate waterproofing, is the landlord’s responsibility to fix.
Tenant’s obligations: Tenants are required to keep the premises clean, notify the landlord of damage, and not cause damage through negligence. A tenant who consistently fails to use a working exhaust fan in the bathroom, who dries laundry indoors continuously without opening windows, or who leaves wet areas in a chronic state of excess moisture may bear responsibility for mould that results from those behaviours.
The “both contribute” scenario: Many Northern Rivers mould disputes involve both factors. A structurally damp house with poor original ventilation where a tenant has also not used exhaust fans presents genuine shared responsibility. In these cases, documentation, by both parties, becomes crucial.
Scenarios and responsibility allocation
Roof leak or plumbing leak causing mould: Clear landlord responsibility. The landlord must repair the leak and remediate the resulting mould. The tenant should report the leak in writing as soon as they become aware of it.
Mould in bathroom with no working exhaust fan: Clear landlord responsibility where the fan was absent or broken at the start of the tenancy, or failed and was reported. The lack of adequate ventilation is a building defect.
Mould in bathroom where exhaust fan is present but tenant doesn’t use it: This is more contested. If the property was in reasonable condition at the start of the tenancy and the mould developed due to the tenant’s ventilation habits, tenants may bear responsibility. However, in the Northern Rivers, even properties with working exhaust fans can develop mould in bathrooms due to ambient humidity, a tenant’s failure to use the fan is not always the decisive factor.
Mould in a sealed wardrobe or behind furniture: Mould in enclosed spaces is typically a consequence of the building’s humidity conditions rather than specific tenant behaviour. This is usually a landlord issue.
Mould following a long-unoccupied vacancy period: Where a property has been vacant and develops mould during vacancy (a significant risk in Northern Rivers’ climate), the resulting mould is a landlord maintenance issue.
The minimum standards framework
Since 2020, NSW residential rental properties must meet minimum habitability standards, which include adequate natural lighting and ventilation in all habitable rooms. Properties where the design or condition of the ventilation system is inadequate for the climate they’re located in, a relevant consideration in subtropical Northern Rivers, may not meet these standards, strengthening a tenant’s position in a dispute.
Practical steps for tenants
- Report mould in writing as soon as you identify it, email or text message with a read receipt provides a dated record
- Photograph all visible mould with timestamps
- Document the ventilation conditions, if there is no exhaust fan, or if the fan doesn’t vent to outside, note this
- Keep records of any symptoms household members experience
- Request a professional assessment if the landlord disputes the cause, an independent mould inspection report is objective evidence
- Escalate to NCAT if the landlord fails to act within a reasonable time. Beyond an order requiring repairs, NCAT can also order a rent reduction for the period the property was affected, see our guide to rent reduction for mould in NSW for how those claims are assessed and what evidence strengthens them
For hosts and property managers dealing with a mould complaint from a short-term guest rather than a long-term tenant, a different set of platform and STRA obligations applies, see our Airbnb mould complaint host playbook for a step-by-step response. And if the property in question is a holiday letting closed up over winter rather than actively tenanted, see our guide to preventing mould during a holiday home shutdown for the pre-close and reopening checklist that avoids the problem in the first place.
Practical steps for landlords
- Inspect the property at the commencement of every tenancy for existing mould and address it before the tenant moves in
- Ensure ventilation systems work, exhaust fans that vent to outside, working range hoods, adequate natural ventilation in all habitable rooms
- Respond promptly to mould reports, a written response within 14 days acknowledging the report and outlining a plan is best practice
- Arrange professional remediation for mould that involves structural moisture or significant growth, don’t just ask the tenant to bleach it
- Document the remediation with photos and a contractor report
If you manage this process across a portfolio rather than a single property, see our step-by-step property manager mould procedure, a repeatable process from intake through to invoicing that keeps the documentation consistent across every file.
FAQs
My landlord in Lismore says the mould is my fault because I didn’t open windows enough. What can I do?
Request a professional mould inspection from an independent assessor. The inspection report will identify moisture sources and likely causes. If the report finds that the mould results from building conditions (inadequate ventilation infrastructure, moisture from the building fabric) rather than occupant behaviour, this supports your position. Take the report to NCAT if the landlord still refuses to act.
How long should a landlord take to fix mould in a rental in Northern Rivers?
For urgent repairs (those affecting health and safety, which serious mould can), the Residential Tenancies Act provides a 24-hour response requirement for emergency contact and a reasonable time to effect the actual repair. For non-urgent repairs, 14 days is a general standard. If mould poses a serious health risk, this should be characterised as an urgent repair in your written request.
Can a landlord deduct from my bond for mould damage at the end of tenancy?
Only if the landlord can establish that the mould resulted from the tenant’s failure to maintain the property appropriately (beyond fair wear and tear) rather than from building conditions. In the Northern Rivers subtropical climate, mould in some form is almost inevitable, a landlord claiming bond deductions for mould must be able to show that the specific mould in question resulted from the tenant’s actions or negligence rather than normal occupation in a high-humidity environment.
What if both the landlord and tenant contributed to the mould problem?
NCAT can apportion responsibility in cases where both parties have contributed. In practice, this is complex, most disputes are resolved before NCAT by negotiation. Where mediation fails and the matter goes to NCAT, an independent professional assessment of the mould’s likely causes provides the most useful evidence for the Tribunal’s decision.
What about mould disputes specifically at the end of a tenancy, over the bond?
End-of-lease mould disputes follow the same responsibility framework but come with their own evidence norms, particularly around what counts as fair wear and tear in a naturally humid climate versus tenant-caused damage. See our dedicated guide to end-of-lease mould disputes for how bond claims involving mould are typically assessed and resolved on the wet north coast.