Bathroom Extractor Fans and Building Regulations Explained
Good ventilation protects your new bathroom from damp and mould — and it is a building regulations requirement. Here is what you need.
Ventilation is one of the most under-rated parts of a bathroom. Get it right and your new bathroom stays fresh and mould-free; get it wrong and you fight condensation forever. It is also covered by building regulations.
What the Regulations Require
Building Regulations Part F sets minimum extraction rates for bathrooms — typically 15 litres/second for a fan, or higher for an internal room with no window. A new bathroom should meet this.
Fan Types
- Axial — for fans ducted a short distance straight outside
- Centrifugal/in-line — for longer duct runs (e.g. internal bathrooms ducting through the loft)
Useful Features
A humidity sensor turns the fan on automatically when moisture rises — far more effective than a timer alone. Quiet "silent" fans (under ~30dB) are worth the small premium.
Don't Forget the Duct
The fan is only as good as its ducting. Short, insulated, smooth ducting to outside (never just into the loft) prevents condensation and keeps performance up.
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Frequently Asked Questions
Do I legally need an extractor fan in a bathroom?
A new or refitted bathroom needs adequate ventilation under Building Regulations Part F. A window alone is often not sufficient, especially for showers and internal rooms.
Are humidity-sensing fans worth it?
Yes — they run exactly when needed, clearing moisture effectively and preventing the mould that timer-only fans often miss.
