Do I Need An Extractor Fan In My Bathroom? (UK)

Do I Need An Extractor Fan In My Bathroom?

Yes…No…It depends.

UK Regulations state: Any new kitchen, bathroom (or shower room), utility room or toilet should be provided with a means of extract ventilation to reduce condensation and remove smells.

If you are refurbishing a bathroom, you will need to ensure that any existing extract ventilation is retained or replaced. If there is no existing ventilation system, you need not provide one (though you can if you wish).

For toilets only, ‘purge ventilation’ (an opening window/door on an external wall) can instead be used to provide ventilation if security is not an issue.

Any extract ventilation system you install should meet the requirements specified in ‘Approved Document F – Ventilation’.

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What Are The Extractor Requirements?

The extractor requirements set out the minimum extraction rate needed for the type of room and type of extractor used.

Building Regulations Part F requires that any intermittent extractor fan in your bathroom must extract at least 15 litres per second (l/s) of air from the room. A continuous extractor fan need only extract 8 l/s.

This is the minimum extraction rate needed to comply with new building regulations. You can, of course, have a more powerful extraction rate. This could be a good idea if your bathroom doesn’t have a window that can be opened or if the bathroom particularly suffers from dampness and mould.

Source: Document F

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What Does An Extractor Fan Do In A Bathroom?

An extractor fan draws in the damp and moist air within a bathroom and expels it through a vent to the outside of a property. By doing this, it means that the moist air isn’t allowed to settle on surfaces and condense into water.

At the same time, this movement of moist air out of the room helps to draw fresh dry air into the room, again, helping to eliminate damp air and the chance of condensation and water settling on surfaces.

If warm moist air is allowed to settle on surfaces and condense this will lead to mould forming. As mould loves a warm, damp environment in which to grow.

Extractor fans not only move the moist air outside of a property but also help to remove any smells in the air as well.

They also play an important role in the larger ventilation and flow of fresh air throughout your home.

What Different Type Of Bathroom Extractor Fan Are There?

For most homes in the UK and most new bathroom extractor fan installations, there are three main options when it comes to picking the type of extractor fan.

These are:

Axial – usually the most common type of extractor fan and what you’re likely thinking of when we talk about bathroom extractors. These are installed directly through an external wall, or in the ceiling using a short duct to reach the outside and vent directly out.

Inline – Typically installed in the ceiling or loft space. An inline fan is positioned in the middle of the vent run between the bathroom vent and the outside of the property.

Because the motor isn’t located in the bathroom these extractors are usually much more powerful and have a larger extraction rate. This means they have enough power to draw moist air along the longer vent runs or are better at tackling bathrooms with bad mould problems.

Centrifugal – Like the axial extractor, centrifugal fans can be installed in the wall or ceiling to be extracted directly out. However, their big advantage is that they can create far more pressure, and as such can extract along much longer vent routes.

They can be a great option if your bathroom doesn’t have an external wall.

The location of your bathroom within your home and any associated installation or construction barriers may mean you have to choose a particular extractor type over another.

bathroom extractor being installed

Do You Need An Extractor Fan In A Bathroom With A Window?

Yes, No, Maybe. Again, this will depend on a few factors.

If the bathroom is part of a new build or a new extension, then yes, you will need to include an extractor fan to comply with UK building regulations. Even if you have a window that can be opened.

If it is an existing bathroom with no extractor and you are simply changing the bathroom suite or updating the existing space with no extension or major building works then you do not need to install an extractor fan.

However, if the existing bathroom has an extractor fan then you must replace it for like-for-like or with an improvement.

If it is a toilet room only (no shower or bath) then as long as you can open the window safely and with no security risks, you do not need to install an extractor fan. This is called ‘purge ventilation’ and is set out in the UK Regulations.

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Are Bathroom Extractor Fans A Standard Size?

Yes. Here in the UK, there are two standard sizes for domestic bathroom extractor fans. A 4-inch (100mm) or a 6-inch (150mm) diameter vent.

A 4-inch model is usually more than enough for most small to medium-sized bathrooms. If you have a larger bathroom or one that is used very regularly (main family bathroom) you may want to opt for the larger 6-inch model to maximise the extraction rate.

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Final Thoughts…

There you have it! Everything you need to know about whether you have to have a bathroom extractor fan.

While it may not be a legal requirement for you to have a bathroom extractor, it’s always good practice to include some form of ventilation in your bathroom.

Not only does it help with nasty smells but it can help improve the longevity of the room and prevent mould and dampness from taking over.


Michael R

Michael is a KBB designer from the UK. He's been designing and project managing new Kitchen, Bedroom and Bathroom installations for over eight years now, and before that, he was an electrician and part of a KBB fitting team. He created The Bathroom Blueprint in early 2020.