Who is responsible for mould in a NSW rental?

It depends on what caused the mould — but in most cases, the landlord has significant legal obligations.

Mould is one of the most common disputes between NSW renters and landlords. It can damage your health, ruin your belongings, and make a home genuinely unpleasant to live in. The good news is that NSW law gives tenants real protections — and in many cases, the law sits firmly on the tenant’s side.

What the law says

Two sections of the Residential Tenancies Act 2010 (the RTA) are the foundation of every mould dispute.

Under section 52 of the Residential Tenancies Act 2010, a landlord must provide premises that are fit for habitation. To be fit for habitation, premises must be structurally sound — which under s52(1B) means the floors, ceilings, walls and supporting structures must not be subject to significant dampness. Premises must also have adequate ventilation (s52(1A)(c)) and adequate plumbing and drainage (s52(1A)(e)).

Under section 63, a landlord must keep premises in a reasonable state of repair throughout the tenancy. This obligation applies even if you knew about the disrepair before you moved in (s63(2)). The landlord is only off the hook if the disrepair was caused by your breach of your tenant obligations under the Act (s63(3)).

Together, s52 and s63 mean that mould linked to building defects, structural dampness, or inadequate ventilation is the landlord’s legal responsibility — full stop.

NSW has not introduced Victoria-style specific mould regulations. There is no standalone mould standard in the Residential Tenancies Regulation 2019. Instead, mould disputes are resolved through s52, s63, and — when urgent — s62.

When mould is the landlord’s responsibility

The landlord is responsible when the mould was caused by something wrong with the building itself.

Common landlord-side causes include: roof leaks, plumbing leaks (including slow drips inside walls), failing waterproofing on balconies or bathrooms, rising damp from the ground, inadequate or broken ventilation systems, and poor building design that traps moisture. If the property had mould before you moved in and the landlord did not disclose it or fix it, that is also the landlord’s problem under s52.

In all of these situations, the landlord is in breach of their s52 and s63 obligations. They must arrange and pay for the mould to be removed, and they must fix the underlying cause.

Even if the mould has spread over time, it does not automatically become your responsibility. The cause is what matters. If the root cause is structural, the obligation stays with the landlord.

When mould might be your responsibility

Tenants have some obligations too — but they are narrower than many landlords claim.

Under the RTA, you must keep premises reasonably clean, and you must notify the landlord promptly of any damage or disrepair. You are also expected to ventilate the property reasonably — for example, by using exhaust fans in bathrooms and kitchens when they are provided.

Mould may be partly your responsibility if: you regularly dried laundry indoors without ventilation, you blocked an exhaust fan or vent, or you left condensation to build up consistently without any ventilation for a long period. Even in these cases, the landlord may still have an obligation to remediate the mould itself, because leaving a health hazard in place is a separate breach from whatever caused it.

If a landlord claims mould is entirely your fault, they need to show that your actions caused the problem — not just that you lived there. You are also not expected to compensate for a building’s inherent problems by, for example, keeping windows open in all weather. If the underlying cause of the moisture is structural — inadequate as-built ventilation, a hidden leak, rising damp — the responsibility stays with the landlord regardless of how you use the property.

When mould becomes an urgent repair

Sometimes mould is serious enough to be treated as an urgent repair under section 62 of the RTA.

Section 62 defines urgent repairs as including any fault or damage that makes the premises unsafe or insecure, and serious roof leaks. Mould can trigger this threshold in two ways. First, if there is an active roof leak causing water ingress and mould growth, that is a serious roof leak under s62. Second, if the mould is significant enough to create a genuine health hazard — particularly for someone with respiratory conditions — it can be characterised as making the premises unsafe.

If a repair is urgent, you can arrange it yourself and seek reimbursement if the landlord cannot be contacted or fails to act promptly. Under section 64, you can spend up to $1,000 on urgent repairs carried out by a licensed tradesperson. You must give the landlord written notice of the repairs and costs. The landlord must reimburse you within 14 days. If they do not, you can apply to the NSW Civil and Administrative Tribunal (NCAT) within 3 months.

For a full breakdown of this process, see our guide on what counts as an urgent repair in a NSW rental.

If the mould makes the property uninhabitable

In severe cases, where extensive mould makes the property wholly or partly uninhabitable, section 109 of the Residential Tenancies Act 2010 may allow you to give the landlord a termination notice that ends the tenancy on the day it is given. Section 43 also automatically reduces (abates) your rent while the premises are uninhabitable.

Section 109 was designed for situations where the premises become uninhabitable through no one’s fault (such as a natural disaster), and landlords sometimes dispute whether it applies to mould caused by disrepair. So this is a significant step — get advice from the Tenants’ Union or a community legal centre before relying on it.

What to do if you find mould

Act quickly — do not wait for mould to spread. Here are the steps.

Step 1: Document everything

Take dated photographs of the mould, including how far it has spread and any nearby structural issues (water stains, cracked sealant, broken vents). Keep a written record of when you first noticed it.

Step 2: Check your condition report

If the mould existed when you moved in and it was not recorded on the ingoing condition report, that strengthens your position. If the landlord disputed the entry at the time, that is recorded evidence too.

Step 3: Notify the landlord in writing

Send a written repair request by email or text — something with a timestamp. State what you found, when you found it, and ask for repairs to be carried out. Keep a copy.

Step 4: Give a reasonable timeframe

For non-urgent repairs, give the landlord a reasonable time — around two weeks is a common expectation, but the Act does not fix a specific number of days. For anything that feels urgent (active leak, widespread mould, health symptoms), use the urgent repair process described above.

Step 4a: Follow up on inadequate repairs

Landlords sometimes perform a quick, superficial fix — painting over mould, running silicone along a suspected leak — rather than addressing the underlying cause. If the mould returns, document this immediately, notify the landlord in writing that the original repair was not effective, and treat this as a fresh (and increasingly serious) breach. A repeated superficial repair is not the same as a genuine fix, and NCAT will look at whether the landlord’s response actually resolved the problem.

Step 5: Escalate if needed

If the landlord ignores you or refuses, you can lodge a complaint with NSW Fair Trading (free and informal). If that fails, apply to NCAT. The Tribunal can order the landlord to carry out specified repairs, reduce your rent for the period the property was in disrepair, and award compensation for damaged belongings or other losses. Note the 3-month application deadline under section 190 of the Act and clause 39(9) of the Regulation — you must apply within 3 months of becoming aware of the breach.

Mould, bonds, and the condition report

Mould can also become a bond dispute at the end of your tenancy. A landlord may try to claim mould remediation costs from your bond.

Whether that deduction is lawful depends entirely on cause. If the mould was there before you moved in, or was caused by a building defect, a bond deduction is not valid. You would dispute it by providing your ingoing condition report, your dated photographs, and your written repair requests showing you reported it. See our guide on how to dispute a bond claim in NSW for the process.

If the mould genuinely resulted from your failure to ventilate, a landlord may have a legitimate claim — but only for the cost directly attributable to your actions, not for pre-existing issues or structural problems.

The most powerful thing you can do is document mould from day one and report it in writing immediately. Written records are the difference between winning and losing a bond dispute or NCAT application.

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