Introduction

If your bathroom ceiling, window seals, or wardrobe corners have developed a mould problem this winter that seemed to appear almost overnight, you're not imagining it and you're not alone. Perth has recorded a wetter-than-average winter in 2026, and property managers, cleaning services, and WA Health information lines are all reporting the same trend: a noticeable spike in mould-related complaints and call-outs across rental properties and owner-occupied homes alike.

This isn't just an inconvenience. Mould is a genuine health and property issue, and in Western Australia it sits at the intersection of tenancy law, building maintenance, and public health guidance — which means getting it wrong can be expensive, whether you're a tenant withholding rent over an unresolved issue or a landlord facing a bond dispute or a liability claim.

This guide breaks down exactly why this winter has been different, who is actually responsible for what under WA's rental framework, the areas of a home most affected right now, and how mould should be properly removed rather than just wiped away and left to return in a fortnight.

 Why Perth's 2026 Winter Has Been a Perfect Storm for Mould

A Wetter, More Humid Season Than Usual

Perth's climate is typically defined by long dry summers and a relatively short, sharp wet season. When winter rainfall and humidity run above the seasonal average, homes that normally dry out between rain events simply don't get the chance to. Persistent dampness in wall cavities, window frames, and bathroom exhaust points creates exactly the conditions mould spores need to establish and spread.

Perth Homes Aren't Always Built for Sustained Humidity

Much of Perth's housing stock, particularly established homes built before more recent energy-efficiency standards, wasn't designed with sustained high humidity in mind. Limited cross-ventilation, older exhaust fan systems, and single-glazed windows all mean condensation has fewer ways to escape once wet weather sets in for an extended stretch.

Heating Habits Make It Worse

As households run heaters more consistently through a colder, wetter winter, the temperature difference between warm indoor air and cold external walls and windows increases condensation on glass and in poorly insulated corners — exactly the surfaces where mould tends to appear first.

H3: Rental Turnover Season Collides With Peak Mould Conditions

Winter is also when a steady flow of leases end and new tenants move in across Perth. That means mould that's developed quietly over several damp weeks is now showing up during final inspections and bond disputes at a higher rate than usual, adding friction to an already stressful part of the tenancy cycle.

Who Is Actually Responsible for Mould in a WA Rental?

This is the question causing the most confusion this winter, and the honest answer is: it depends on the cause.

When It's Likely the Landlord's Responsibility

Under WA's Residential Tenancies Act, landlords are generally responsible for maintaining a rental property in a reasonable state of repair. If mould is caused by a structural issue — a leaking roof, faulty plumbing, rising damp, broken window seals, or an exhaust fan that isn't functioning — that typically falls on the landlord or property manager to fix, not just clean.

When It's Likely the Tenant's Responsibility

If mould develops primarily due to how a property is being lived in — windows kept shut with no ventilation, wet towels left in a closed bathroom, or an exhaust fan never being used — a tenant may be expected to manage day-to-day cleaning and reasonable ventilation practices themselves.

 Why This Matters More Than Ever This Season

Because this winter's mould surge is being driven partly by genuine weather conditions rather than tenant behaviour alone, both landlords and tenants are being encouraged to document issues early with photos and written communication, rather than letting the problem sit until a final inspection turns it into a bond dispute.

 The 7 Areas Seeing the Biggest Mould Spike This Winter

 1. Bathroom Ceilings and Exhaust Fan Surrounds

The most commonly reported area this season. Sustained humidity combined with inadequate exhaust ventilation is producing visible black mould spotting on bathroom ceilings faster than in a typical Perth winter.

2. Window Seals and Frames

Condensation build-up on single-glazed windows is showing up as mould along silicone seals and frame edges, particularly in bedrooms and living areas that aren't ventilated during the day.

 3. Wardrobe Interiors and Built-In Robes

Enclosed, poorly ventilated wardrobe spaces are a common but often-missed mould location, especially in homes where clothing is stored against an external wall.

 4. Shower Grout and Silicone

Persistent humidity is accelerating mould growth in shower grout lines and around silicone seals, even in bathrooms that are cleaned regularly, because the underlying moisture problem isn't being addressed.

5. Behind and Under Furniture Against External Walls

Furniture positioned tight against external walls restricts airflow, and this winter's sustained dampness is showing up as mould patches behind beds, wardrobes, and lounges in a growing number of call-outs.

 6. Laundry Areas With Limited Ventilation

Laundries without adequate exhaust ventilation are seeing increased mould around walls and ceiling corners, particularly in homes doing more indoor drying due to the wetter weather.

7. Roof Cavities and Ceiling Corners in Older Homes

In established homes with ageing insulation or ventilation gaps, ceiling corners and roof cavity edges are showing early mould signs that often go unnoticed until they're more advanced.

 Why Wiping Mould Isn't the Same as Removing It

A quick wipe with a standard household cleaner might lift the visible surface mould, but it typically doesn't address the spores that have already spread into grout, silicone, paint, or porous surfaces. That's why mould so often reappears within weeks of a DIY clean, especially during a wetter season when the underlying humidity problem hasn't gone anywhere.

Proper mould remediation involves treating the surface with the right product for the material involved, addressing porous areas thoroughly rather than just the visible patch, and — critically — identifying whether a ventilation or moisture issue needs to be fixed at the source to stop it coming straight back.

What a Professional Mould Clean Should Include

• Assessment of affected areas and likely moisture source
• Treatment of grout, silicone, and porous surfaces, not just visible mould
• Bathroom and laundry exhaust point cleaning
• Window seal and frame detailing
• Wardrobe interior and behind-furniture treatment where accessible
• Safe, appropriate product use for each surface type
• Recommendations for ongoing ventilation to prevent recurrence

A Perth Team Who Understands This Season's Conditions

SAS Cleaning Service has seen the increase in mould-related clean requests first-hand this winter, across both rental properties preparing for inspection and family homes noticing the problem for the first time. We treat mould properly rather than masking it, and we're upfront with clients about whether what they're dealing with looks like a cleaning issue or a maintenance issue that needs a tradesperson involved as well.

Dealing With Mould This Winter? Don't Wait It Out.

Whether you're a tenant trying to protect your bond, a landlord managing a maintenance request, or simply noticing mould in your own home for the first time this season, SAS Cleaning Service can help you deal with it properly before it spreads further.

📞 Phone: 0478 367 089 📧 Email: contact@sascleaningservice.com 📍 Location: 11/10 Morley Drive, Tuart Hill, WA 6060 — servicing Perth and all surrounding suburbs