Bathroom Resealing and Mould Prevention

Why bathroom seals fail in the first place

The silicone around your shower, bath and basin does a simple but important job: it keeps water out of the gaps where two surfaces meet. Over time that silicone shrinks, hardens and pulls away from the edges. Once there's a gap, water seeps behind the tiles and into the wall cavity, and that's where the real trouble starts.

In Melbourne, the mix of cold, damp winters and bathrooms that don't get much airflow makes this worse. Warm showers plus poor ventilation equals condensation sitting on cold surfaces for hours. That's exactly the environment mould loves.

Signs it's time to reseal

You don't need to guess. Look for these:

• Black or pink staining along the silicone lines that won't scrub off
• Silicone that's lifting, cracking or peeling away from the tile or bath
• Gaps you can slide a fingernail into
• A musty smell that lingers even when the room looks clean
• Loose or "drummy" tiles near the shower base

If you spot any of these, water is likely already getting in. The longer you leave it, the more damage happens behind the wall where you can't see it.

How resealing is actually done

A proper reseal isn't just running a new bead of silicone over the old one. That's the most common mistake, and it always fails. The right process looks like this:

1. Remove all the old silicone. Every bit of it, using a scraper and solvent so nothing's left to trap moisture.
2. Clean and treat the area. Kill any existing mould and remove soap scum so the new sealant can bond.
3. Dry it completely. Silicone won't cure properly on a damp surface. This step gets skipped a lot and it's why DIY reseals peel.
4. Apply quality mould-resistant silicone. Neatly tooled, with the right product for wet areas.
5. Leave it to cure. Usually 24 hours before the shower gets used again.

Choose the right silicone

Not all silicone is equal. For bathrooms you want a neutral-cure, mould-resistant sanitary silicone rated for wet areas. Cheap general-purpose stuff discolours fast and doesn't hold up.

Preventing mould from coming back

Resealing fixes the symptom, but ventilation fixes the cause. A few habits make a big difference:

• Run the exhaust fan during every shower and for 15-20 minutes after
• Leave the door or window open to let humidity escape
• Wipe down glass and tiles with a squeegee after showering
• Check your fan actually vents outside, not just into the ceiling cavity — a surprising number of Melbourne homes have fans that dump moist air into the roof space
• Keep an eye on grout as well as silicone; cracked grout lets water in too

If mould keeps returning in the same place despite all this, there's usually a deeper issue — a failed waterproofing membrane or water tracking behind the tiles. That's worth investigating before it becomes a bigger repair.

When to call in a hand

Resealing a single straight run is a doable weekend job if you're patient and tidy. But if you've got multiple wet areas, awkward corners, signs of water damage, or mould that keeps coming back, it's worth getting it done properly the first time. A messy or rushed reseal usually needs redoing within a year.

If your bathroom's due for a reseal or the mould won't quit, MB Handymen & Carpentry can strip the old silicone, treat the mould, reseal it cleanly and check the surrounding grout and ventilation while we're at it — handy to bundle with any other small repairs on your list.