Bathroom building regulations: Part P, F, G, H and accessibility
A bathroom is a regulated, "special location" for good reasons — water and electricity, ventilation, scald safety and drainage. Here is what the rules actually require, in plain English.
In short
- ✓Part P — electrics in bathroom "zones" need the right IP rating; mains sockets and standard switches are restricted; work is certified by a registered electrician.
- ✓Part F — bathrooms need mechanical extraction of at least 15 litres/second, ideally with a 15-minute over-run.
- ✓Part G — new bath hot water must be limited to 48°C via a thermostatic mixing valve (TMV) to prevent scalding.
- ✓Part H — waste runs need the correct fall (typically 1:40) and proper soil-stack venting. Part M / BS 8300 set accessible dimensions.
What building regulations apply to a bathroom?
A bathroom installation can engage several parts of the Building Regulations: Part P (electrical safety), Part F (ventilation), Part G (hot-water safety and water efficiency) and Part H (drainage). Accessible bathrooms also follow Part M and BS 8300. Creating a new bathroom or moving services usually needs the relevant work certified and signed off.
What IP rating does a shower light need?
Under Part P, fittings in Zone 1 (directly above the bath or shower up to 2.25m) need a minimum of IP44, with IP65 the practical standard to resist direct spray. Zone 0 (inside the bath/shower) needs IPX7 and only low-voltage fittings. All bathroom electrical work should be carried out and certified by a registered electrician.
Does a bathroom legally need an extractor fan?
If a bathroom has no openable window — or you’re creating a new one — Part F requires mechanical extraction of at least 15 litres per second. Best practice is to fit the fan high, opposite the door, with a 15-minute over-run timer so it clears humidity after the light goes off, protecting against condensation and mould.
Part P — electrical safety and zones
Bathrooms are "special locations". Fittings are rated by zone:
- •Zone 0 (inside bath/shower): IPX7, low-voltage only.
- •Zone 1 (above, to 2.25m): IP44 minimum, IP65 recommended.
- •Zone 2 (0.6m beyond): IP44 minimum.
- •Standard switches and 230V sockets are restricted; work is certified by a registered electrician.
Part F — ventilation
Humid air must be removed to prevent condensation and mould. The minimum for an intermittent extractor fan is 15 litres/second; fit it high (within ~400mm of the ceiling), opposite the main air source, ideally with a 15-minute over-run after the light is switched off.
Part G — hot water safety
To prevent scalding, hot water to a new bath must be limited to a maximum of 48°C using a thermostatic mixing valve (TMV) located close to the outlet. Stored hot water is kept hotter for hygiene and blended down at the point of use.
Part H & accessibility (Part M / BS 8300)
Waste pipes need the correct continuous fall (typically around 1:40) and soil stacks must be properly vented. Accessible bathrooms follow Part M and BS 8300 — clear turning space, comfort-height WCs, grab-rail positions and lever, thermostatic taps. See our accessible bathrooms service for how this is designed in.
Compliance is part of the job, not an afterthought
We plan to these standards from the design stage and arrange the certified trades (registered electricians for Part P, correct ventilation and TMVs) so the work is compliant and signed off. You should expect the relevant certification on completion — it protects your home and your insurance, and it is something cheaper "cash jobs" routinely skip.
Frequently asked
Do I need building control sign-off for a bathroom?+
Simple like-for-like replacements often don’t, but creating a new bathroom, adding an en-suite, or new electrical circuits and drainage typically do. Certified competent persons (e.g. a registered electrician) can self-certify their parts. We handle the compliant trades as part of the project.
Who is responsible for making my bathroom compliant?+
The work must be done by competent people to the regulations. We design to the standards and coordinate the certified trades through our vetted local network, providing the compliance documentation at handover.