Bathroom mould is the single most common complaint we get from Sunshine Coast clients, and most of the advice circulating online doesn’t account for what coastal humidity actually does. After working on bathrooms across the coast for years, here’s the genuinely useful version of what works and what doesn’t.

The honest starting point is that you can’t eliminate mould in a coastal bathroom. Our humidity is high enough year-round, our nighttime temperatures are mild enough, and our bathroom usage patterns produce enough moisture that the conditions for mould are present most of the time. The realistic goal is keeping it from establishing visibly and from causing material damage. Total elimination is the wrong target.

What genuinely helps

Ventilation is the single biggest factor and the one most people get wrong. The standard exhaust fan in a typical coastal bathroom runs while someone’s in the shower and shuts off when the timer or the user does. That’s not enough. The bathroom needs to keep ventilating after the person has left, until the surfaces have actually dried.

Practical version: run the exhaust fan for at least 20 minutes after every shower. If you have a manual switch, leave it on when you walk out and a partner or housemate or your future self can turn it off later. If you have a timer, set it to 20 minutes. If your fan doesn’t have a timer, change it to one that does — these are now $80 to $150 fans that any electrician can swap in 20 minutes.

The next factor is the silicone seal around wet zones. Tired silicone is the single biggest entry point for water into surfaces that should be dry, and it’s the place where mould establishes most reliably. Silicone seals around showers, baths and basins should be inspected annually and replaced when they show any sign of pulling away from the surface, discolouring, or cracking. The cost of replacement is small. The damage from leaving it is large.

Grout sealing is more nuanced than the marketing suggests. Properly sealed grout in a bathroom that’s well-ventilated will resist mould for years. Grout that’s been left unsealed in a bathroom that’s poorly ventilated will absorb moisture continuously and become a permanent mould reservoir. The annual reseal that gets recommended is overkill for most situations and not enough for the worst situations. The right answer is to inspect the grout each year, reseal where it’s clearly tired, and treat any visibly mouldy grout as a sign of a deeper problem.

What doesn’t help

Bleach treatments. Bleach removes the visible colour from surface mould but doesn’t address the mould itself. The mycelium — the network of mould underneath the visible spots — remains intact. The mould comes back, often within a few weeks, sometimes faster. Bleach also damages grout sealers and silicone over time, making the next round of mould worse.

Anti-mould paint. Some of the products marketed as anti-mould paint do help. Most of them are general-purpose paints with marketing claims that aren’t supported by independent testing. The paints that actually work are the specialist anti-microbial bathroom paints from established manufacturers, and they help most where the underlying ventilation is also addressed. Painting over a mouldy surface in a poorly ventilated bathroom buys six months at best.

Aromatic mould inhibitors. The clip-on tablets and gel pots marketed for ongoing mould prevention have negligible effect against the actual conditions in a coastal bathroom. They smell pleasant. They don’t change the moisture or the surface conditions in a meaningful way.

What I do at home

Our team runs the same approach in our own homes. Three things, consistently:

Run the exhaust fan after every shower for the actual time it takes to dry the bathroom. On a humid summer day that’s longer than it is on a cool dry winter day. Pay attention to the surfaces and adjust accordingly.

Wipe down the shower walls after use. The squeegee is the cleaning industry’s quiet secret. Thirty seconds with a squeegee on the shower walls after each use removes most of the residual moisture before it has time to be absorbed. The reduction in mould pressure over time is substantial. The marriage-saving version of this is to make it a one-person job rather than a shared chore that doesn’t get done.

Tackle small mould spots immediately when they appear. A dilute white vinegar solution (three parts vinegar to one part water), left on the affected area for 15 minutes, then scrubbed lightly with an old toothbrush, removes most early-stage mould properly. Dried surfaces afterwards. This treatment, applied early and consistently, prevents the mould reservoir from establishing in the first place. The same approach applied after the mould has been visible for months is much less effective.

The structural questions

Some bathrooms have structural problems that no amount of cleaning addresses. The signs are specific.

Persistent mould patterns on ceilings, particularly near walls and corners, often indicate inadequate exhaust capacity or poorly directed exhaust ducting. Older houses sometimes have exhaust fans that vent into the roof cavity rather than to outside, which creates the conditions for mould throughout the roof space and recirculation back into the bathroom.

Mould patches that recur in the same locations after repeated cleaning point to either a slow leak (most commonly a tap fitting, sometimes a hidden waste pipe) or a thermal bridge where condensation forms preferentially. Either way, the structural issue needs addressing.

Mould around windows or external walls in a bathroom usually indicates moisture penetration from outside rather than internal moisture, particularly on coastal homes where wind-driven rain comes from the south-east. The fix is at the building envelope, not in the bathroom routine.

If you’re seeing any of these patterns, the bathroom cleaning routine is downstream of a building issue. We can clean the visible mould, but it will come back unless the structural piece gets addressed.

What we’d recommend for a coastal home

The realistic prevention programme for a bathroom on the Sunshine Coast looks like this. Run the fan properly. Squeegee the shower. Inspect the silicone annually and replace where tired. Inspect the grout annually and reseal where needed. Treat early mould spots immediately with vinegar. Get a proper bathroom deep clean once or twice a year to address what builds up despite everything else.

This combination, applied consistently, keeps coastal bathrooms in good shape. The standard one-bottle-of-bleach-and-hope approach doesn’t.