Many single-storey rear and side-return extensions in London do not need planning permission. They are covered by permitted development rights, provided they stay within the limits. This guide explains those limits, the options if you want to build bigger, and what else your project needs before it starts.
When you do not need planning permission
A single-storey extension is usually permitted development if it meets all of the following:
- It extends no more than 3 metres beyond the rear wall of the original house for a terraced or semi-detached house, or 4 metres for a detached house.
- It is no more than 4 metres high.
- It does not extend forward of the principal elevation (the front) or side elevation that faces a road.
- A side extension is single storey, no more than 4 metres high, and no more than half the width of the original house.
- The materials are similar in appearance to the existing house.
- There are no verandas, balconies or raised platforms.
Building a bigger rear extension
If you want to extend further than 3 or 4 metres, there is a separate route called the neighbour consultation scheme (often called prior approval). Under it, a single-storey rear extension can go up to 6 metres for a terraced or semi-detached house, or 8 metres for a detached house, provided the design meets the rules and the neighbours are consulted. This is a lighter process than a full planning application, but it is not automatic.
When you will need planning permission
You will normally need a full planning application if any of the following apply:
- You want a double-storey or wrap-around extension.
- Your home is a flat or maisonette.
- Your property is in a conservation area or covered by an Article 4 direction.
- Your project exceeds the size or height limits above.
- Your home is listed.
A householder planning application is normally decided within eight weeks, and the majority are approved.
Building regulations always apply
Every extension needs building regulations approval, whether or not planning permission is required. This covers foundations, structure, drainage, insulation, fire safety, glazing and electrics. Building control inspects the work at key stages and issues a completion certificate at the end.
The Party Wall etc. Act 1996
Extensions almost always involve building near or on a boundary, and often excavating for foundations close to a neighbour’s property, which brings the Party Wall etc. Act 1996 into play. You must serve notice before work starts. See our guide to party wall agreements.
How we help
LET-HD Developments manages the whole process, including drawings, structural calculations, building control and any planning or prior-approval application. We tell you clearly at the survey stage which route your project needs. You can read more about our house extension service.
Frequently asked questions
Do side-return extensions need planning permission?
Usually not, if they are single storey, no more than 4 metres high and no more than half the width of the original house. A wraparound extension that turns the corner usually does need permission.
How close to my neighbour can I build?
There is no fixed distance in planning terms, but the Party Wall etc. Act sets rules for excavation near a neighbour’s foundations. We handle the notices and any surveyor appointments.
What if my neighbour objects to a planning application?
Objections are considered, but they do not automatically stop an application. Most householder applications are approved, often after small design changes.
Check whether your extension needs permission
Call +44 (0) 203 355 5313 or use our contact form and we will tell you what applies to your property, free of charge.