Mould in the shower: clean it, reseal it, or look for a leak
Mould in a shower is usually surface mould on grout and silicone, fed by steam and water that never quite dry. Clean what's on the surface. If black spots stay in the silicone after cleaning, the mould is inside it and the sealant needs cutting out and replacing. If it keeps coming back fast in one spot, check for a leak behind the tiles.
Why showers get mouldy
A shower is wet several times a day, and the corners, grout lines and sealant never get long enough to dry out between uses. Steam that isn't cleared quickly settles on the coldest surfaces in the room, and the sealant along the tray or bath stays damp longest. Add soap residue for the mould to feed on and it doesn't take long for grey or black spots to appear.
The extractor fan decides a lot. If there isn't one, it's too weak, it's clogged with fluff, or it's wired to switch off with the light, the steam lingers. You'll often see the same mould spreading to the ceiling above the shower; our guide to mould on a bathroom ceiling covers that side of it.
Clean or reseal?
Tiles and grout. Spray a mould-killing product on the tiles and grout, leave it for the time on the label, then scrub the grout lines with an old toothbrush or a soft brush and rinse. Grout that's stained deep down, crumbling or cracked is better raked out and replaced than scrubbed again and again.
Silicone sealant. Give it one proper clean. If the black is still there once it's dry, the mould has grown into the silicone, and no spray will reach it. Cut the old sealant out with a sharp blade, clean and treat the gap, then leave it to dry completely before you put new silicone in. Resealing over damp or mouldy edges just traps the problem underneath. A bathroom silicone with mould resistance is worth paying a little extra for.
Don't rely on bleach. It can lighten the stain on sealant and grout without killing what's grown into it, and the black comes back. Our pillar guide on how to get rid of mould covers safe cleaning in more detail.
What to do this week
- Run the extractor fan while you shower and for 15 to 20 minutes after, with the door shut.
- Check the fan works: hold a sheet of toilet paper near it while it's on. If it barely moves, the fan needs cleaning or replacing.
- Open the window after showering if there is one.
- Squeegee or wipe the tiles, screen and tray after use so they dry faster.
- Leave the shower door or curtain open afterwards, and spread the curtain out to dry.
- Wash or replace a mouldy shower curtain rather than leaving it bunched up and damp.
When it points to a leak
Most shower mould is condensation and splashing. A leak looks different, and it won't stop however well you ventilate:
- tiles that feel loose or sound hollow when tapped
- grout or sealant that keeps cracking or going black within weeks in the same spot
- a stain on the ceiling of the room below, or damp on the other side of the shower wall
- a musty smell that lingers when the bathroom is dry
- flooring that's soft or lifting near the tray
Water getting behind tiles or under a tray can soak the wall and floor for a long time before it shows. If you see these signs, get it looked at before it does more damage. A damp and mould survey can confirm where the water is going.
Your health
The NHS asthma causes page lists mould as one of the things people can be allergic to that sets off asthma. Official guidance for landlords in England, Damp and mould: understanding and addressing the health risks for rented housing providers (MHCLG, DHSC and UKHSA), says damp and mould mainly affect the airways and lungs. If someone at home has asthma or a mould allergy, keep the bathroom ventilated and speak to your GP if their breathing gets worse.
When to get a specialist
Bring in a specialist if there are signs of a leak, if mould is spreading beyond the shower onto walls and ceilings, or if it comes back quickly even with a working fan. They can check behind the tiles, find the water, and deal with the damp as well as the mould. Tell us about the problem and we'll pass it to one independent local specialist to quote. It's free to ask.
If you rent: wiping the shower down is everyday upkeep, but if mould keeps coming back, or the fan, the sealant or a leak looks like the cause, report it to your landlord in writing with photos. Our tenants' guide explains what they must do and by when.
If you're a landlord: a report of mould in the shower may be more than cleaning: check the fan, the sealant and any sign of a leak. Under Awaab's Law in Scotland, the investigation clock starts the day after you're told. Our landlords page explains the rules, and the deadline calculator works out the dates.
Last checked 26 October 2026. This is general guidance, not legal or building advice.
Common questions
Can you clean black mould off shower silicone?
If it's only on the surface, a mould spray and a soft brush can shift it. If black spots are still there after cleaning, the mould has grown into the sealant, and the only real fix is to cut the old silicone out, let the area dry fully and reseal it.
How long should the extractor fan run after a shower?
Keep it running while you shower and for 15 to 20 minutes afterwards, with the door shut. If the mirror is still steamed up long after you've finished, the fan probably isn't moving enough air.
Why does the mould only come back in one corner of the shower tray?
It can be a spot where water sits after every shower. If the sealant there keeps going black soon after it's replaced, or the grout keeps cracking, water may be getting behind it, and that's worth having checked.
Get a free quote
This is a free matching service, not the firm doing the work. We pass your details to one independent damp and mould specialist who covers your postcode. They contact you, arrange a visit and quote you directly. You don't pay us anything.