VENTILATION
A fan that keeps up
Approved Document F gives a minimum intermittent extract rate of 15 l/s for a bathroom. With no openable window, the fan should run on for at least 15 minutes after you leave.
See the numbers
WHAT THE GUIDANCE SAYS
A new en suite,
built to the rules.
Installing a bathroom that involves plumbing is one of the jobs that may need building regulations approval.
England's Approved Documents set out how to meet the rules: enough extraction to clear steam, a place to wash hands by every WC, a door between any WC and the kitchen, and limits on bath water temperature in new homes.
15 l/s intermittent extract for a bathroom
Check a feature- Check approval first
- Clear the steam
- Wash hands, keep food apart
- Small room, real rules
THE SHORT ANSWER
Check approval,
then plan the details.
Building regulations approval is different from planning permission.
You might need both.
APPROVAL
New plumbing counts
GOV.UK lists installing a bathroom that will involve plumbing among jobs that may need approval. Using a registered competent person scheme installer means you do not need to get approval yourself.
Check a feature
HYGIENE
A basin by every WC
Every extra toilet should have its own hand washing facility, in the same room or in an adjacent space that is the only way in.
Plan the room
FOUR THINGS TO PLAN
Plan it on paper
before the pipes go in.
A simple order of questions to raise with your builder or building control body, based on GOV.UK and the Approved Documents.
Ask about approval
Check whether your work needs building regulations approval, or use an installer registered with a competent person scheme.
Plan the extraction
Allow for a fan at 15 l/s, mounted high, with a 15-minute run-on if the room has no openable window.
Let air move
Internal doors should allow air to pass, equivalent to a 10 mm undercut on a 760 mm wide door.
Place the basin and doors
Put a hand basin in the WC room or its only way in, and keep a door between the WC and any kitchen.
TWO NUMBERS WORTH KNOWING
One for the steam,
one for the bath.
Both figures come straight from
England's Approved Documents.
15 l/s
Minimum intermittent extract rate for a bathroom
Table 1.1 sets 15 litres a second for a bathroom, 6 for a room with only a WC. Fans should sit as high as practicable, no more than 400 mm below the ceiling.
VENTILATION · APPROVED DOCUMENT F
48°C
Maximum temperature of water delivered to a fixed bath
Requirement G3(4) says the hot supply to any fixed bath must not deliver water above 48°C, in new dwellings and those formed by a material change of use.
HOT WATER · APPROVED DOCUMENT G
When a kitchen or bathroom is refurbished, Approved Document F says any existing extractor fans should be retained or replaced, and checked to see they work properly.
A QUICK FEATURE CHECK
What do the rules
say about this?
Pick a feature of your en suite to see what England's building regulations guidance says. The bar shows how widely the point applies to an en suite added to an existing home.
From GOV.UK and Approved Documents F (ventilation, dwellings) and G (sanitation and hot water safety), England.
WHY IT MATTERS
Certificates count
when you sell.
GOV.UK warns that the person doing the work could be prosecuted and fined if building regulations are not followed, and the building control body could make you pay to fix faulty work.
Without approval, you will not have the certificates of compliance you may need when you come to sell your home. Swapping an extractor fan on existing cabling, Approved Document F notes, does not need to be notified.
Questions
Questions people ask
Do I need building regulations approval for an en suite?
You might. GOV.UK lists installing a bathroom that will involve plumbing among the projects that may need approval. Check with a building control body if you cannot decide.
How powerful should a bathroom extractor fan be?
Approved Document F gives a minimum intermittent extract rate of 15 litres per second for a bathroom, with a 15-minute run-on where there is no openable window.
Does an en suite need its own basin?
Approved Document G says each additional toilet should have an associated hand washing facility, in the same room or an adjacent space that is the only way in.
Can a toilet open straight onto a kitchen?
A room with a WC or its hand basin should be separated from any kitchen or food preparation area by a door. In homes, a room with both a WC and a basin does not need a separate lobby.
Is there a limit on bath water temperature?
For new dwellings and those formed by a material change of use, the hot supply to a fixed bath must not deliver water above 48°C.
Sources
- GOV.UK: Building regulations approval, when you need approval
- GOV.UK: Ventilation, Approved Document F
- GOV.UK: Sanitation, hot water safety and water efficiency, Approved Document G
- Approved Document G with 2024 amendments (PDF)
Updated