Winter’s Dirtiest Secret: How to Stop Bathroom Mould Before It Takes Over

You crank up the hot shower, steam fills the room, and somewhere behind your tiles — mould is quietly winning.

Winter is peak season for bathroom mould, and it spreads faster than most people realise. Here’s how to get ahead of it.

Why Winter Makes It Worse

Cold air outside + hot steam inside = condensation sitting on every surface. Couple that with windows staying shut and bathrooms drying out slower, and you’ve got the perfect breeding ground. Mould can start forming on grout, silicone and ceiling corners within 24–48 hours of consistent moisture.

The Spots Most People Miss

Everyone sees the grout. But mould hides in:

• The silicone seal around your bath and shower base (it goes black from the inside out — by the time you see it, it’s deep)

• Extractor fan covers — dust and moisture combine and sit there untouched for months

• Behind shampoo bottles and soap dishes — zero airflow, constant moisture

• The underside of your toilet cistern — condensation drips and pools beneath it all winter

What Actually Works (And What Doesn’t)

• Doesn’t work: Bleach sprayed and wiped straight off — it kills surface mould but doesn’t penetrate grout or silicone. The mould comes back within weeks.
• The right method for grout: Apply a bleach-based gel (like Selleys Rapid Mould Killer or similar), leave it for 10–15 minutes covered with cling wrap to keep it wet, then scrub with a stiff grout brush. The dwell time is what does the work.
• For silicone that’s gone black: If mould has penetrated the silicone, cleaning won’t fix it. It needs to be cut out and resealed. It’s a 20-minute job but most people avoid it for years.
• For ceilings: Use a microfibre pad on an extendable handle rather than a sponge. Sponges drip contaminated water straight into your eyes and onto surfaces below.

The Habit That Prevents 80% of the Problem

Run your extractor fan for at least 15 minutes after every shower — not just during it. Most people turn it off when they leave the room. That’s when the condensation is actually sitting on the walls.

No extractor fan? Crack a window or leave the door open. Airflow is the single biggest factor in bathroom mould prevention.

When to Call It In

If mould is appearing on the ceiling in multiple spots, returning within weeks of cleaning, or you can smell it but not fully see it, it’s likely behind the wall or in the ceiling cavity. That’s not a cleaning job, that’s a remediation job, and worth getting assessed before it spreads further.

Jim’s Cleaning offers professional bathroom and mould cleaning services right across Australia. Find your local Jim’s Cleaning team at www.jimscleaning.com.au.