How do I stop mould coming back in a bathroom?
Removing it is the easy part — the ventilation and habits that stop it returning are what actually matter.
- Difficulty
- beginner
- Time
- 1 hr
- Read
- 2 min
- Safety
- caution
Short answer
Mould returns because the moisture does. Run the extractor for 20 minutes after every shower, leave the door shut while it runs, and squeegee the walls. Cleaning without changing the ventilation is a monthly chore forever.
A bathroom generates a large amount of moisture in a short time in a small room. Mould is the visible consequence, and treating it as a cleaning problem rather than a ventilation problem is why it always comes back.
Safety
Step by step
- Clean the existing mould properly.A mould remover or diluted bleach on hard surfaces, left to work rather than scrubbed immediately. Ventilate and wear gloves and a mask.
- Replace mouldy silicone rather than cleaning it.Once mould is inside the sealant it cannot be cleaned out. Cut it out, clean and dry thoroughly, and reseal with a mould-resistant sealant.
- Run the extractor fan for 20 minutes after showering.The critical habit. Most people turn it off with the light. An overrun timer or a humidity-sensing fan does it automatically and is a cheap upgrade.
- Keep the door closed while the fan runs.Otherwise the moist air moves into the rest of the house and condenses in the coldest room instead. Door shut, fan on, window open a little if there is one.
- Check the fan actually works.Hold a sheet of paper to it — it should hold it in place. Many bathroom fans are blocked, disconnected, or vent into the loft rather than outside.
- Squeegee the walls and screen after showering.Thirty seconds removes most of the water before it can evaporate into the room. It makes a genuine difference.
- Keep some background heat in the room.Warm surfaces do not condense. A cold bathroom in winter is where condensation forms first, regardless of ventilation.
- Dry towels and bath mats elsewhere.They hold a surprising amount of water and release it slowly into the room all day.
Tips
- A humidity-sensing extractor fan is the single best upgrade for a mould-prone bathroom. It runs when needed and stops when it is not.
- Anti-mould paint helps, but only once the moisture is under control. On a wet wall it fails like any other paint.
- If there is no window and no working fan, that is the problem. Everything else is managing a symptom.
Common mistakes
- Turning the fan off with the light — The moisture is still in the air when you leave. The twenty minutes afterwards is when the fan does most of its work.
- Painting over mouldy sealant — Mould grows within silicone and cannot be sealed over. It has to be cut out and replaced.
Questions people ask
Why does mould keep coming back after I clean it?
Because the moisture that caused it has not changed. Cleaning removes the growth; ventilation removes the cause.
How long should a bathroom fan run?
At least 15-20 minutes after showering, with the door closed. An overrun timer or humidity sensor does this without anyone remembering.