Every accommodation manager we deal with has the same recurring line item: the same bathrooms, the same ceilings, mould back within months of the last clean. The instinct is to blame the cleaner, the occupant or the climate. It’s usually none of those. It’s the exhaust fan.
A bathroom is designed to dry itself
Every commercial bathroom and ensuite is built around a simple assumption: the steam a shower generates gets pulled out through the exhaust fan within minutes of use. AS 1668.2 sets the mechanical ventilation rates that assumption relies on. Get that airflow and the surfaces dry before anything can take hold.
Lose it and the room stops drying. Moisture sits on the ceiling, in the grout and behind the silicone - and mould does what mould does with a damp surface and no light.
Why the fan quietly stops working
Bathroom exhaust fans fail slowly, which is exactly why nobody notices. The impeller picks up a felt of lint and dust. The duct behind it collects the same. The discharge point at the roof or eave silts up with debris. Each of those costs a little airflow.
None of it stops the fan. It still spins, still makes noise, still looks like it’s working. It just isn’t moving much air. We regularly open units pulling a fraction of what they were installed to pull, in rooms where somebody has been scrubbing the ceiling twice a year for a decade.
Camp ensuites are the worst case
If you run accommodation in the Pilbara, you already know this one. A mine village runs hundreds of near-identical ensuites at high occupancy, often through a wet season, in rooms built to a price. Every one of those fans loads up at the same rate - which means when they go, they go as a fleet.
That’s why the mould complaints tend to arrive in a batch rather than one at a time, and why cleaning them one at a time never gets ahead of it.
Cleaning the mould is treating the symptom
We remediate mould for a living, so this isn’t us talking ourselves out of work. But the IICRC S520 principle we work to is source removal: you deal with what caused the growth, not just the growth itself. In a bathroom, the source is almost always moisture with nowhere to go.
Remediate the ceiling without restoring the extraction and you’ve booked the same job again next year. Restore the extraction and the remediation actually holds.
What a proper exhaust clean covers
Rather more than pulling the grille off and rinsing it:
- Grille - removed, washed and sanitised, not wiped in place
- Impeller and housing - the felted lint stripped back to clean blades
- Motor - condition and run check while the unit is open
- Duct interior - the section nobody ever looks at
- Discharge point - roof cowl or eave vent cleared and confirmed open
- Airflow - measured before and after, so the improvement is a number
That last one matters. Without a before-and-after reading you have no evidence the clean achieved anything, which is no use to you at an audit or in a dispute with a builder.
Put it on an interval
For most accommodation, strata and institutional bathrooms, an annual exhaust clean keeps extraction where it should be - more often for high-occupancy blocks or humid environments. It costs a fraction of repeat mould remediation, and it’s far easier to schedule than an outbreak.
If you manage bathrooms around Perth or the Pilbara that keep growing mould back, get in touch. We’ll measure what the fans are actually pulling and tell you honestly whether it’s a clean or something bigger.