How do I stop mould coming back in the bathroom?

Bathroom mould is entirely a moisture problem. Cleaning it removes the symptom, and it returns within weeks unless the room dries out between uses. A bathroom that's dry within an hour of a shower rarely grows mould at all, whatever cleaning you do or don't do.

What you'll need

• Squeegee
• Mould remover
• Hygrometer (optional)
• Extractor fan with a timer or humidistat (optional)

Step by step

1. Test whether the extractor fan actually works.Hold a sheet of tissue paper against the grille with the fan on. If it doesn't hold, the fan is blocked, failing or ducted badly.
2. Run the extractor during the shower and for 20 minutes afterwards.Most of the moisture leaves the room after you do. Fans wired to the light switch stop far too early.
3. Keep the bathroom door closed while showering and for a while after.It contains the moisture in the room where the extractor can remove it, rather than spreading it through the house.
4. Open the window after showering, once the extractor has done its work.Cross-ventilation clears remaining humidity quickly.
5. Squeegee the screen, tiles and bath after every use.Thirty seconds. It removes most of the standing water in the room and prevents limescale at the same time.
6. Hang towels to dry properly, or take them out of the room.Wet towels bunched on a rail keep the room humid for hours and grow their own smell.
7. Clean existing mould with a proper mould remover, and replace mouldy silicone.Mould grows into silicone rather than on it. Once it's in, no cleaner reaches it — see the resealing guide.
8. Check the humidity with a cheap hygrometer if it keeps recurring.Sustained readings above 60% mean the ventilation isn't adequate for how the room is used.
9. Consider upgrading the extractor to one with a humidistat or timer.It runs until the room is actually dry rather than for a fixed period, which is the reliable fix.

Tips

• A bathroom with no window and a weak extractor will always struggle. Upgrading the fan is usually the single most effective spend.
• Anti-mould paint helps on a ceiling that keeps spotting, but only after the ventilation is addressed.
• Leave the shower screen or curtain open after use so it dries rather than staying folded and wet.
• Check the extractor duct isn't crushed, blocked or terminating in a loft. A fan venting into a roof space creates a much bigger problem than it solves.

Common mistakes

• Cleaning the mould but not changing the ventilation — It returns within weeks. The moisture is what's feeding it.
• Assuming the extractor works because it makes noise — Many are blocked, badly ducted or underpowered. Test with tissue paper.
• Leaving the door open while showering — It spreads the moisture through the house instead of containing it where the extractor can remove it.
• Cleaning mouldy silicone repeatedly — Once mould is growing inside the silicone, no cleaner reaches it. It needs replacing.

Questions people ask