The short answer
A bathroom must meet Building Regulations covering electrics (Part P), ventilation (Part F) and drainage (Parts G and H). Electrical work in a bathroom is notifiable under Part P and must respect the IP-rated zones around water; mechanical extract ventilation is required under Part F; and any drainage and waste work must comply with Parts G and H. A qualified installer handles compliance and certification.
You do not usually need to think about Building Regulations on a like-for-like bathroom replacement — but the work still has to comply, and parts of it are notifiable. Knowing which rules apply helps you check your installer is doing things properly. This guide explains the main Approved Documents that affect bathrooms in plain English.
Bathroom regulations at a glance
- Electrics Part P — notifiable, IP-rated zones
- Ventilation Part F — extract fan required
- Sanitation Part G — sanitary fittings
- Drainage Part H — waste and soil
- Costliest compliance Moving the soil stack
- Who certifies Registered installer / building control
Part P: electrical safety and zones
Electrical work in a bathroom is one of the more tightly regulated areas of home wiring because of the obvious danger of water and electricity together. Under Approved Document P, electrical installation work is notifiable, meaning it must be either carried out by an installer registered with a competent person scheme who self-certifies, or notified to building control. Bathrooms are also divided into IP-rated zones around the bath and shower, and fittings within each zone must carry the right protection rating. An electric or power shower, fan, downlights and a heated towel rail all fall under these rules. Our shower types guide notes where electrical work applies.
Part F: ventilation
Approved Document F requires extract ventilation in a bathroom to remove the moisture that causes damp and mould. In practice that means an adequately sized extractor fan ducted to outside. Ventilation is cheap to fit during a renovation and prevents expensive damage later — our ventilation and damp guide covers it in full.
| Approved Document | Covers | Bathroom relevance |
|---|---|---|
| Part P | Electrical safety | Notifiable wiring; IP zones |
| Part F | Ventilation | Extract fan required |
| Part G | Sanitation, hot water safety | Sanitary fittings, scald risk |
| Part H | Drainage and waste disposal | Soil, waste, falls |
Parts G and H: sanitation and drainage
Approved Document G deals with sanitation and hot water safety, and Part H with drainage and waste disposal. Any new or altered soil, waste and drainage work must comply — pipes correctly sized and laid to the right falls, and connections made properly. This is why moving the WC or the soil stack is the costliest change in a bathroom: it is not just labour, it is regulated drainage work that has to be done correctly. Our cost guide and en-suite guide explain the cost impact.
When do you need building control involvement?
A straightforward like-for-like bathroom replacement generally does not require a building control application, but the work must still comply and notifiable electrical work must be certified. Bigger changes — structural alterations, a new en-suite in a loft, or adding a bathroom as part of an extension — can bring building control and even planning permission into play. Our planning permission guide covers when planning is needed. This page is general information; confirm the requirements for your project with your installer or local authority.
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Frequently asked questions
Do I need Building Regulations approval to replace a bathroom?
A like-for-like replacement generally does not need a building control application, but the work must still comply with the regulations, and notifiable electrical work under Part P must be certified. Bigger changes, such as a new en-suite or an extension, can require building control.
Is bathroom electrical work notifiable?
Yes. Under Part P, electrical installation work in a bathroom is notifiable and must be either self-certified by a registered competent person or notified to building control. Bathrooms also have IP-rated zones that dictate which fittings can go where.
What are bathroom electrical zones?
Bathrooms are divided into zones around the bath and shower based on the likelihood of contact with water. Each zone requires fittings with an appropriate IP protection rating, so lights, fans and other fittings must be suitable for their location.
Why is moving the toilet so expensive?
Relocating a WC means new soil and waste drainage laid to the correct falls and compliant with Parts G and H. It is regulated drainage work, not just plumbing, which makes it the costliest single change in most bathroom projects.
Sources & further reading
- GOV.UK / Building Regulations Approved Document P — electrical safety
- GOV.UK / Building Regulations Approved Documents F, G and H
- CIPHE — plumbing and drainage standards
- TrustMark — finding a vetted tradesperson for home improvement work
This is general information, not advice for your specific property or installation. Requirements vary with your home and the scope of work. Bathroom Answers is an independent information and introduction service, not an installer.