Damp, mould & air
Bathroom extractor fans: the unsung heroes
The bathroom extractor is the hardest-working machine nobody thinks about, and plenty of them are quietly doing nothing behind a decade of dust. Here is how to test yours in ten seconds, clean it in ten minutes, and choose a replacement that earns its keep.
By the Tickover team · Published 23 January 2026 · 4 min read
The toilet-paper test
Run the fan and hold a single sheet of toilet paper flat against the grille. A working fan pins it there, no hands needed. If it flutters and falls, the fan is not moving enough air to matter, and every shower is feeding condensation and black mould somewhere in the room.
A bathroom fan exists to export steam before it settles. Building regulations expect an intermittent bathroom fan to shift about 15 litres of air a second, and a grille furred with dust can lose half its performance while sounding exactly the same. Dust is also the cheapest fault to fix in this article.
The ten-minute service
Clean it properly
Kill the power first
Switch off at the isolator (often a ceiling pull cord or a fused switch outside the room), or turn the circuit off at the consumer unit.
Ease the grille off
Most unclip or release with one central screw. Note how it fitted.
Wash the grille
Warm soapy water, then dry it fully before it goes back.
Vacuum the visible dust
Soft brush attachment around the blades and housing. No dismantling; the casing stays on.
Refit and retest
Power back on, then repeat the toilet-paper test. No grip means the problem is deeper: duct, shutter or motor.
Features that matter
| Feature | What it does | Verdict |
|---|---|---|
| Overrun timer | Runs 5–15 minutes after you leave | Standard; have it |
| Humidistat | Switches on when the air turns damp | Great for showers |
| Continuous (dMEV) | Low trickle all day, boost on demand | Good for problem rooms |
| Backdraught shutter | Stops cold draughts when off | Cheap comfort win |
Wherever the fan lives, the duct must finish outside: a wall grille, a soffit vent or a tile vent. A surprising number are found lying disconnected in the loft, exporting every shower into the insulation, where it condenses and grows mould on the rafters. If the loft above your bathroom smells musty, look.
Sizing, in plain terms: match or beat the extraction rate printed on the box (quoted in litres per second), choose a centrifugal or inline model when the duct run is long, and pick one with a backdraught shutter unless you enjoy a draughty ceiling in January. A fan that works is the single biggest lever on bathroom damp.
Replacing one
Fitting or swapping a bathroom fan is electrician territory. Bathrooms have defined electrical zones, and fan wiring often ties into the lighting circuit with a timer feed, so this is not a DIY connection: see what you can and cannot touch. The good news is that it is a small, quick job for a professional.
Extractor rules
Do
- Run it for every bath and shower, all year round
- Clean the grille at least twice a year
- Keep the door shut so it pulls steam, not landing air
- Check the duct ends at an outside grille, not in the loft
Don’t
- Do not switch it off at the isolator and forget it exists
- Do not vent it into the loft or a wall cavity
- Do not wire or replace one yourself; bathroom zones are electrician work
- Do not expect an open window to do the job in January
Replacement, installed
Like-for-like fan swap
new ducting adds to the bill
Electrician hourly rate
Typical UK ranges, mid-2026, as a guide only. Your home, your area and the job itself all move the number — always compare real quotes.
Not sure what you’re dealing with?
Fan humming, rattling or doing nothing at all? Run it through Self-Diagnose in the Tickover app for a likely cause and an urgency read, with a vetted electrician lined up if it needs one.
Quick answers
How long should an extractor fan run after a shower?
Around 15 minutes is a sensible benchmark, and some humidistat models keep going until the moisture level actually drops, which is better still. If your fan stops the instant the light goes off, steam is left to settle on the coldest surfaces. An overrun timer is a small upgrade that does the remembering for you.
Why is my bathroom fan so weak?
Dust is the usual culprit: a furred grille and blades can halve the airflow. After that, look for a kinked, crushed or blocked duct, a backdraught shutter stuck shut, or a fan that was undersized for the room in the first place. Clean it, retest with the toilet-paper trick, and if it still fails, price a replacement.
Can I fit a bathroom extractor fan myself?
Cleaning the grille is yours; installation and replacement belong to an electrician. Bathrooms have defined electrical zones with rules about what can go where, and fan wiring is often fed from the lighting circuit through a timer. A like-for-like swap typically costs £150–£350 installed, more if new ducting is needed.
Do I need a fan if the bathroom has a window?
A window helps in summer and does very little on a cold, wet January evening, when opening it dumps heat and chills the room. Extraction works in all weathers, automatically, every shower. If a window-ventilated bathroom is growing mould on the ceiling or sealant, that is your answer: fit a fan.
This guide is general information for UK homes, not advice about your specific property. Anything involving gas must be done by a Gas Safe registered engineer, and notifiable electrical work by a qualified electrician. If you smell gas, call the National Gas Emergency line on 0800 111 999. If you’re ever unsure, stop and get a professional in — that’s exactly what Tickover is for.
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