Property Manager's Guide to Mould: Legal Obligations & Best Practice

Mould is one of the most common maintenance issues property managers deal with in Sydney — and one of the most legally sensitive. Handle it well and it's a routine repair. Handle it poorly and you're looking at tribunal claims, health complaints, and damage to your agency's reputation. This guide covers what you need to know to manage mould issues confidently, from first report to resolution.

Your legal obligations in NSW

Under the Residential Tenancies Act 2010 (NSW), landlords — and by extension, their managing agents — must ensure the property is provided and maintained in a reasonable state of repair, considering the age, character, and prospective life of the premises.

Mould caused by structural issues (leaks, poor ventilation design, inadequate waterproofing, rising damp) is the landlord's responsibility. The property must be fit for habitation, and persistent mould from building defects makes a strong argument that it is not.

Mould caused by tenant behaviour (failing to ventilate, drying clothes indoors without ventilation, not using exhaust fans, not reporting leaks promptly) is more nuanced. Even in these cases, the landlord still has an obligation to address the mould if it reaches a point where it affects habitability — though responsibility for the underlying cause may sit with the tenant.

Key obligations:

• Respond promptly to mould reports — a "we'll get to it" approach creates liability
• Investigate the cause — don't just treat the symptom. If mould is growing, moisture is getting in from somewhere
• Remediate appropriately — the standard of repair should match the severity. A wipe with bleach is not adequate remediation for a recurring or extensive mould problem
• Document everything — inspections, reports, communications, quotes, and remediation records
• Follow up — confirm the issue is resolved and monitor for recurrence

The NSW Civil and Administrative Tribunal (NCAT) has consistently held that landlords must address mould promptly and effectively. Claims for rent reductions, compensation, and lease termination due to unresolved mould are increasingly common — and tenants are winning them.

For a deeper look at tenant and landlord rights, see our article on mould in rental properties.

When a tenant reports mould

This is your workflow. Every time.

Step 1: Acknowledge immediately

Reply within 24 hours. Even if you can't inspect immediately, acknowledge the report and confirm your next steps. Written communication (email or your property management platform) creates a timestamped record.

Step 2: Inspect and document

Attend the property as soon as possible — ideally within 3–5 business days for non-urgent reports, within 48 hours if the tenant reports health symptoms or extensive visible mould.

During inspection, document:

• Location and extent of all visible mould (photos with date stamps)
• Moisture readings if you have a moisture meter (inexpensive and worth carrying)
• Potential sources — check for leaks (plumbing, roof, windows), condensation patterns, and ventilation
• Tenant behaviour factors — are exhaust fans being used? Is there evidence of wet clothes drying indoors? Are windows ever opened?
• Condition of ventilation — are exhaust fans working? Do bathrooms and laundries have adequate extraction?
• Duration — when did the tenant first notice it? Has it been reported before?

Step 3: Assess severity

Not all mould reports are equal:

Minor — small patches (under 1 square metre) on hard surfaces in wet areas. Likely addressable with a professional clean and improved ventilation.

Moderate — mould on multiple surfaces, on porous materials (plasterboard, carpet), or recurring after previous treatment. Needs professional assessment and remediation.

Severe — extensive mould, mould in concealed spaces (wall cavities, subfloor), signs of toxic mould, or tenants reporting health symptoms. Needs urgent professional assessment, possible temporary relocation, and formal remediation.

Step 4: Engage the right trades

For minor issues, a qualified cleaner with mould experience may suffice. For moderate to severe problems, use a professional mould remediator — not a general handyman, not a painter, and definitely not "just get the cleaner in."

Why this matters: a handyman who paints over mould creates a hidden problem that will return worse. A professional remediator identifies the cause, removes the mould correctly, treats the air, and provides documentation that protects you and your owner.

Step 5: Address the cause

Remediation without fixing the moisture source is a waste of money. Common causes in Sydney rental properties:

• Bathroom exhaust fans venting into the ceiling cavity instead of outside
• Blocked or damaged gutters causing water ingress
• Failed waterproof membranes in bathrooms and laundries
• Subfloor ventilation issues in older homes
• Window and door seals deteriorating
• Plumbing leaks — often slow and hidden

Coordinate the building repair alongside or before the mould remediation. If the cause requires significant building work, keep the tenant informed about timelines.

Step 6: Follow up

Check back 4–6 weeks after remediation. Look for any signs of recurrence. Document the follow-up inspection. This closes the loop and demonstrates due diligence.

Documentation: your best protection

In any mould dispute — whether at NCAT, through a complaint to NSW Fair Trading, or in correspondence with a difficult tenant — documentation wins. Keep records of:

• Initial tenant report (date, method, content)
• Your response (date, what you said, what you committed to)
• Inspection photos (date-stamped, geotagged if possible)
• Moisture readings and observations
• Quotes obtained from remediators
• Owner communication — your recommendation, the owner's approval (or refusal)
• Scope of work from the remediation company
• Completion report including any testing results
• Follow-up inspection records
• Tenant communication throughout

If an owner refuses to authorise necessary mould remediation, document that refusal in writing. Your obligation as the agent is to recommend the appropriate course of action — if the owner declines, you need that on record.

Communicating with tenants about mould

Mould is an emotional issue. Tenants worry about their health and their children's health. A dismissive or slow response damages trust fast.

Do:

• Acknowledge their concern genuinely
• Explain what you're going to do and when
• Be transparent about timelines — if the owner needs to approve costs, say so
• Provide interim advice (increase ventilation, keep affected doors closed, use a dehumidifier)
• Follow through on every commitment
• Share remediation reports and test results

Don't:

• Blame the tenant in your first response — even if tenant behaviour is a factor, lead with action, not accusation
• Minimise the issue — "a bit of mould is normal in Sydney" may be true but is not what a worried parent wants to hear
• Promise outcomes you can't control — say "we're getting a professional assessment" not "we'll have it fixed by Friday"
• Go silent — radio silence is the single biggest accelerator of tribunal complaints

The commercial property dimension

If you manage commercial properties — offices, retail, warehouses — mould obligations extend further:

• Work Health and Safety Act 2011 (NSW) — the PCBU (person conducting a business or undertaking) must ensure the workplace is safe. Mould affecting indoor air quality is a WHS issue.
• Air quality standards — commercial tenants may have lease clauses requiring specific air quality standards
• Business interruption — mould remediation in a commercial space can mean lost trading days. Your response time directly affects your client's financial exposure.
• HVAC systems — commercial buildings with shared air conditioning systems can spread mould contamination across multiple tenancies

For commercial mould issues, engage a remediator experienced with commercial properties and compliance documentation.

Building a preferred supplier relationship

Having a trusted mould remediation partner on your trades list saves time and improves outcomes. Look for:

• Experience with rental properties — they understand the documentation and communication requirements
• Professional testing capability — not just treatment, but before-and-after testing that provides evidence
• Detailed reporting — written scope, photos, findings, and recommendations you can share with owners and tenants
• Non-toxic treatment methods — important for occupied properties and for reducing your liability. Natural treatments like SAN-AIR mean the property can be reoccupied faster with no chemical exposure concerns.
• Transparent pricing — clear quotes that you can present to owners with confidence

Prevention: the routine inspection checklist

Add these checks to your routine property inspections:

• [ ] Bathroom exhaust fans operational and venting to outside
• [ ] Rangehood operational and venting to outside
• [ ] No visible mould on walls, ceilings, window frames, or grout
• [ ] No musty odours
• [ ] Windows and doors sealing properly
• [ ] No evidence of water staining on ceilings or walls
• [ ] Gutters and downpipes clear (visual check from ground level)
• [ ] Subfloor vents unblocked (for houses with subfloor)
• [ ] Air conditioning filters clean (ask tenant about maintenance)
• [ ] No rising damp signs on ground-level walls

Catching issues early at routine inspection is vastly cheaper than dealing with a mould complaint.

Need help?

Pureairo works with property managers across Sydney to handle mould issues quickly, professionally, and with the documentation you need. We offer free assessments, detailed written reports, non-toxic SAN-AIR remediation, and post-treatment verification testing. Whether it's a single unit or a whole building, get in touch and we'll make it straightforward.