Homeowners · Permissions and rules

Planning, building regulations and party walls

These are three different things. A job can need one, two or all three. Ask about all three at the start.

Information, not legal advice. This guide explains official rules in plain words for England, with links to the sources. Rules change and every job is different, so check the source or get advice for your situation. Last checked 24 October 2026.

Planning permission

Planning permission is about whether you can build something at all: its size, look and use. Some smaller extensions to houses can go ahead under permitted development rights without a planning application (GOV.UK).

• Permitted development rights for extensions apply to houses, not to flats or maisonettes (Planning Portal).
• Your council may have removed some rights in your area with an Article 4 direction (Planning Portal). Conservation areas and listed buildings have extra rules.
• Under permitted development, a single-storey rear extension can generally go back up to 4m for a detached house or 3m for other houses. This can go up to 8m or 6m under a prior approval process, and other conditions apply (Planning Portal; GOV.UK technical guidance).
• If you build without permission you need, the council can issue an enforcement notice (GOV.UK).

The Planning Portal says it is your responsibility to check whether you need planning permission (Planning Portal). Your builder can help, but agree in writing who is doing what.

Building regulations

Building regulations are about how the work is done: structure, fire safety, insulation, drainage and so on. They apply to extensions and to many alterations. GOV.UK lists examples including replacing fuse boxes and connected electrics, bathrooms involving plumbing, replacing windows and doors, replacing roof coverings, and installing or replacing a heating system (GOV.UK). Some work is exempt (GOV.UK).

• If your installer is in a competent person scheme, they can self-certify the work and you do not need to apply separately (GOV.UK).
• Otherwise you use either your local authority building control or a registered building control approver (GOV.UK).
• A full plans application gets a decision within 5 weeks, or 2 months if you agree. With a building notice, work can start 2 days after you submit it (GOV.UK).
• At the end you should get a completion certificate. GOV.UK says this usually comes within 8 weeks of the work being completed. You will need it when you sell (GOV.UK).
• If work was done without approval, you may be able to apply for regularisation for work carried out after 11 November 1985 (GOV.UK).
• If the rules are not followed, the person doing the work can be prosecuted, and you may have to pay to put it right (GOV.UK).

Party walls

The Party Wall etc. Act 1996 applies in England and Wales. You must tell your neighbours if you plan to work on a shared wall, build on the boundary, or dig near their foundations (GOV.UK).

• Notice is usually given between 2 months and a year before work on a party wall starts (GOV.UK; Act, s.3).
• For a new wall on the boundary line, or for excavation near a neighbour's foundations, the notice period is 1 month (Act, ss.1 and 6).
• A neighbour has 14 days to consent in writing. If they do not respond, or they dissent, there is a dispute and surveyors prepare a party wall award (GOV.UK).
• An award can be appealed to the county court within 14 days (GOV.UK).

Who serves the notices and who pays for the surveyors should be in your contract with the builder.