Ventilation
Bathroom extractor fans and ventilation explained
Most black mould in bathrooms is a ventilation problem. Moving moist air out quickly is the fix, and the fan is only part of it.
If your mirror is still fogged ten minutes after a shower, or black spots keep coming back on the ceiling, the room is not getting rid of moist air fast enough. The fix is usually better ventilation: an extractor that suits the room, placed where the steam collects, with a way for fresh air to replace what it removes.
We fit extractor fans and improve ventilation as part of our bathroom fitting work. This guide explains what matters, in plain terms, so you can judge the fan you have and the one you might need.
Why bathrooms get so wet
A hot shower puts a lot of water into the air. When that warm, damp air meets a cold wall, window or ceiling, it turns back into water. Repeat that every day and the surfaces stay damp long enough for mould to grow, paint to peel and sealant to blacken.
This is condensation, and it is the most common cause of mould in bathrooms. It is different from rising or penetrating damp, which come from outside the room. Those need to be surveyed properly, and damp proofing is a separate service that we survey and quote separately.
What a good extractor does
An extractor fan pulls moist air out before it settles on cold surfaces. To do that well, it needs to move enough air for the size of the room, and it needs to keep running for a while after the shower is off, because the air stays humid for some time.
- Sized to suit the room rather than the cheapest option
- An overrun timer or humidity sensor so it keeps working
- Quiet enough that nobody switches it off
- Ducted to the outside, not into a loft space
Position matters as much as the fan
Steam rises and gathers near the ceiling above the shower or bath. A fan placed close to that point, and away from the door, draws moist air across the room and out. A fan in the wrong corner can run all day and barely touch the problem.
Replacement air matters too. If the door seals tightly and there is no gap underneath, the fan has nothing to pull in, and its performance drops. A small gap under the door is usually enough.
Why a renovation is the best time
During a refit the ceiling and walls are open, so running a new duct, moving the fan to a better spot or adding wiring for a humidity sensor is far easier. Doing it later means cutting into new tiles or a fresh ceiling.
It is also the time to deal with the effects of past condensation. Stained plaster can be repaired or skimmed, and mould damaged sealant replaced, so the new room starts clean.
Simple habits that help
A fan works best alongside a few everyday habits. None of them replace proper extraction, but together they make a noticeable difference.
- Leave the fan running after a shower
- Keep the door closed while showering so steam goes out, not into the house
- Wipe down glass and tiles after use
- Keep the room gently heated in cold weather
Questions
Frequently asked
Why is my bathroom mould coming back after cleaning?
Usually because moist air is not being removed quickly enough. Cleaning treats the mould, but better ventilation stops it returning.
Where should a bathroom extractor fan go?
High up near the shower or bath, where steam collects, and ideally on the opposite side of the room from the door.
Can you replace my extractor fan?
Yes. Extractor fans and improved ventilation are part of our bathroom fitting work.
Is condensation the same as damp?
No. Condensation comes from moisture inside the room. Rising and penetrating damp need a survey, and damp proofing is quoted separately.
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