Is the mould on the silicone or under it?
- On the surface: the marks wipe or scrub lighter, the silicone is still soft and stuck firmly to the tiles, and the mould comes back slowly.
- Under or inside: the black spots don't change no matter what you use, you can see them through the silicone, the silicone is lifting, split or peeling at the edges, or there's a gap behind it.
If it's under the silicone, cleaning won't fix it. The only fix is to remove the silicone, treat and dry the joint, and reseal.
How to clean mould off shower silicone (surface mould)
- Ventilate: open a window or run the exhaust fan, and wear gloves.
- Use a mould remover made for bathrooms and follow the label. Never mix cleaning products, especially bleach with ammonia or acid-based cleaners.
- Apply it to the silicone, leave it for the time on the label, then rinse well.
- Dry the area completely. Mould needs moisture, so drying the shower after use makes the biggest difference.
- If you have epoxy grout, check your aftercare guide before using strong chemicals. We recommend pH-neutral cleaners on our epoxy grout.
What actually causes mould in shower silicone
The real culprit is usually the grout, not the silicone. Standard cement grout on your shower walls and base is porous: it soaks up water every time you shower. That water runs down inside the grout lines and gets trapped behind the silicone in the corners and along the base, where it can't dry out. Trapped moisture plus warmth equals mould, growing behind and underneath the silicone where no cleaner can reach it.
That's why replacing the silicone on its own usually doesn't last. The new silicone looks great for a while, but the cement grout keeps feeding water in behind it, and the mould comes back.
How to stop the mould coming back
When to replace shower silicone
Replace it when:
- The mould is under or inside the silicone
- The silicone is peeling, split, hard or lifting
- There's a gap between the silicone and the tile or base
- The bottom of the wall or the base gets damp, or you've noticed a leak
Silicone is a maintenance item. Even good silicone needs replacing every few years in a busy shower.
What a professional silicone replacement involves
- Cut out all the old silicone, including the bits that hide in the joint.
- Treat the mould and let the joint dry.
- Check the grout next to it. If it's cement grout, water will keep getting behind the new silicone. For a lasting fix, regrout with epoxy as well.
- Apply new sanitary-grade, mould-resistant silicone, tooled into a clean, watertight bead.
Can I just put new silicone over the old?
No. New silicone won't bond properly to old silicone, and you'd be sealing the mould and moisture in. The old silicone has to come out completely first.
FAQs
Why does mould keep coming back on my shower silicone?
Usually because porous cement grout is soaking up water and trapping it behind the silicone. Cleaning or replacing the silicone alone won't stop it. Regrouting with non-porous epoxy grout and resealing fixes the cause.
Is black mould in the shower dangerous?
Mould in damp areas can affect people with allergies, asthma or breathing problems. If you're worried about your health, talk to your doctor. Removing the source of moisture is the long-term fix.
How often should shower silicone be replaced?
It depends on use and ventilation, but silicone is a maintenance item. Replace it as soon as it's peeling, split, lifting or has mould underneath.
How much does it cost to replace shower silicone in Melbourne?
From $450 + GST for silicone replacement only. If grout also needs work, see our shower regrouting prices.
How long before I can use the shower after new silicone?
We'll confirm the exact time on the day, as it depends on the product used.
Send photos for a fixed quote
Send a photo of the whole shower or balcony and a close-up of the grout. We assess the visible condition and explain whether regrouting and resealing are suitable.