How to Remove Bathroom Mould and Stop It Coming Back
Black silicone sealant, spots on the ceiling? How to safely remove bathroom mould, when to call a professional, and how to stop it returning.
The bathroom is where mould appears most often: showering creates lots of moisture that condenses on cold surfaces. The good news is that you can remove small patches yourself, and a few habits will keep it from coming back.
Is it really mould?
Not every dark spot is mould. Typical signs:
- black, grey or greenish dots that spread across an area
- a musty smell
- patches in cold spots: corners of outside walls, above the window, on the ceiling, in silicone joints
Pink or reddish slime in the shower is usually bacteria, not mould. It’s unpleasant but easy to remove with a normal bathroom cleaner.
DIY or professional?
| Situation | Recommendation |
|---|---|
| Small, surface patches under about 0.5 m² | remove yourself |
| Black silicone sealant | replace the sealant |
| Area larger than about 0.5 m², or deep in the plaster | professional |
| Mould returns quickly | have the cause checked (thermal bridge, leak?) |
| Allergies, asthma, pregnancy or small children at home | professional, don’t remove it yourself |
Removing mould from walls and ceilings
You’ll need: disposable gloves, an FFP2 mask, safety glasses, 70% alcohol (ethanol or isopropanol) or a hydrogen peroxide-based mould remover, disposable cloths and a bin bag.
- Put on protection and open the window.
- Don’t brush it off dry: that releases spores into the air.
- Apply the product: wet the area generously and let it work (follow the manufacturer’s instructions).
- Wipe off with disposable cloths and put them straight into a bag you can seal.
- Repeat until no discolouration is visible.
- Let it dry thoroughly and ventilate well.
Caution: alcohol is flammable, so keep it away from open flames and ventilate well. Hydrogen peroxide can lighten coloured surfaces; test on an inconspicuous spot first.
On painted surfaces, you can repaint after drying with a breathable paint (e.g. silicate or lime paint). Painting over mould without removing it does not help; it keeps growing underneath.
Black silicone sealant: replace, don’t scrub
Mould in silicone grows into the material. Surface cleaning only lightens the joint briefly. The only lasting fix is replacing it:
- Cut out the old silicone with a sealant knife or utility knife.
- Loosen residues with a silicone remover and clean the joint thoroughly.
- Degrease and disinfect with alcohol and let it dry completely (ideally overnight).
- Apply sanitary silicone with fungicide and smooth it with a joint tool and a little soapy water.
- Don’t shower for at least 24 hours.
Causes: why does bathroom mould appear?
Mould mainly needs moisture. The most common reasons:
- Not ventilating enough after showering or bathing
- Cold wall surfaces (outside walls, thermal bridges) where steam condenses
- A bathroom that is kept too cold
- Drying laundry in the bathroom without an extractor
- Leaking pipes or joints that let water into the wall or floor
How to prevent it for good
- Air out after showering: open the window wide for 5–10 minutes and keep the door to the rest of the home closed.
- No window? Let the extractor fan run for at least 15–30 minutes afterwards and clean the vent regularly.
- Squeegee the water: drying tiles and the shower screen removes a lot of moisture from the room.
- Keep the bathroom warm: don’t let it drop below about 20 °C.
- Dry towels and bath mats elsewhere if the bathroom is small.
- Hang a hygrometer: humidity should be back under 60% within an hour.
Frequently asked questions
Does vinegar kill mould?
Vinegar is often recommended but isn't a good choice: on lime-based surfaces such as plaster the acid can be neutralised, and organic residues can even feed mould. 70% ethanol or isopropanol, or hydrogen peroxide solutions, work better.
Should I use bleach?
Chlorine bleach mainly lightens mould and irritates the airways and skin. Consumer and health agencies advise against it indoors. Never mix it with other cleaners.
Who pays for mould in a rented flat?
It depends on the cause. A building defect (e.g. a thermal bridge or leaking pipe) is the landlord's responsibility; inadequate ventilation or heating may make the tenant responsible. Always report mould to your landlord in writing straight away.
What humidity is normal in a bathroom?
70–80% right after a shower is normal. What matters is that humidity falls back below 60% within about an hour. A cheap hygrometer tells you whether your ventilation is enough.