In short: Replacing a bathroom in the same layout generally does not require building regulations approval. Approval is needed where you add new electrical circuits, alter drainage, make structural changes, or create a bathroom in a room that was not one before. Ventilation requirements apply either way.
What's in this guide 8 sections
01 The short version
Swapping a bath, basin and toilet for new ones in the same positions is a repair-and-replace job and is generally not notifiable. As soon as you start changing where things are, adding circuits, or turning a bedroom into a bathroom, building regulations become relevant.
This guide covers England and Wales. Scotland and Northern Ireland have their own, broadly similar systems.
02 What is notifiable and what is not
| Work | Notifiable? |
|---|---|
| Replacing a suite in the same position | No |
| Re-tiling and redecorating | No |
| Replacing an extractor fan like for like | No |
| Adding a new electrical circuit | Yes — Part P |
| Installing electric underfloor heating on a new circuit | Yes — Part P |
| Moving the toilet or altering the soil pipe | Yes — Part H |
| Creating a bathroom or WC in a room that was not one | Yes |
| Removing or altering a load-bearing wall | Yes — Part A |
| Installing a macerator WC | Usually yes, as a drainage alteration |
| Fitting a new window or altering an opening | Yes — Parts L and F |
03 Electrical work: Part P
Bathrooms are "special locations" under Part P because of the combination of water and electricity, and the rules are stricter than in other rooms. Adding a new circuit is notifiable; so is any work within the defined shower and bath zones.
Fittings must carry an appropriate IP rating for the zone they sit in, and everything must be protected by an RCD. Notifiable work must either be carried out by an electrician registered with a competent person scheme such as NICEIC or NAPIT, who can self-certify it, or be notified to building control in advance.
The certificate matters beyond compliance. When you sell the house, the buyer's solicitor will ask for it, and its absence can hold up or reduce a sale.
04 Drainage: Part H
Moving a toilet is the alteration most likely to trigger building regulations, because it involves the soil pipe rather than simple pipework. Soil runs need a consistent fall of roughly 1 in 40 to work, which is why where a WC can go is decided by the drainage, not by the layout you would prefer.
Macerator installations are normally treated as drainage alterations too. They are a legitimate solution where a gravity run is impossible, but a gravity run is always the better answer where one is achievable.
05 Ventilation: Part F
Every bathroom needs adequate ventilation. In practice, a room without an openable window requires mechanical extraction with an overrun timer, and even with a window an extractor is normally expected in a room containing a shower.
This is the requirement most often quietly ignored, and the consequences show up as condensation, mould and, in a well-insulated modern house, damage to the plaster and decoration within a couple of winters.
06 Structural work: Part A
Removing the wall between a bathroom and a separate WC — one of the most common bathroom alterations in inter-war and post-war housing — is only a stud partition in most cases and is not structural. In some houses it is doing work, and taking it out without support is dangerous.
The answer is to establish which you have before demolition, not during it. Where a wall is load-bearing, the opening needs a properly sized lintel or beam, usually to a structural engineer's design, and it is notifiable.
07 How approval actually works
- Full plans application — drawings submitted to building control before work starts. Used for structural work and larger projects.
- Building notice — a simpler route for smaller domestic work, notifying the council shortly before starting.
- Competent person self-certification — for notifiable electrical work carried out by a registered electrician, and the most common route for a bathroom.
- Regularisation — a retrospective application where work has already been done without approval. Possible, but slower, more expensive and it may require opening finished work up.
Your local authority is Bolsover, Bassetlaw, Mansfield, Chesterfield, Ashfield, North East Derbyshire, Rotherham or Newark & Sherwood depending on where the property sits. Fees and processes vary slightly between them.
08 What to expect from a competent contractor
A good contractor tells you at quotation stage which elements of your project are notifiable, who will certify them, and what documentation you will receive at the end. That conversation should happen before you accept a quote, not after work has started.
If a quote is silent on the subject and the job clearly involves new circuits or moved drainage, ask directly. The answer will tell you a great deal about the company.