Do I need planning permission for a rear extension in South West London?
Many rear extensions don't need a planning application — but the rules are specific, and some South West London areas have restrictions that catch homeowners out. Here's what you need to know.
By Distinct Spaces · Updated June 2026 · 6 min read
The good news: a single-storey rear extension on most South West London houses is permitted development — meaning you don't need a planning application. The less good news: the permitted development rules have size limits, and several areas across Richmond, Kingston and Twickenham have Article 4 Directions or conservation area restrictions that change the picture.
Getting this wrong is a serious problem. Building without the correct consent, or building larger than permitted development allows, is a planning breach. It can lead to enforcement action and will appear as a problem when you come to sell. This guide explains where the rules sit and what you need to check.
Single-storey rear extensions: the permitted development limits
Under permitted development, a single-storey rear extension on a house is allowed without a planning application as long as:
Depth limit — standard
For a detached house: up to 4 metres from the original rear wall. For a semi-detached or terraced house: up to 3 metres from the original rear wall. "Original" means the rear wall as it was when the house was first built (or as it stood on 1 July 1948 for older properties).
Depth limit — larger home extension scheme
Under the Neighbour Consultation Scheme (often called Prior Approval), you can build up to 8 metres (detached) or 6 metres (semi/terraced) from the original rear wall. This requires notifying the council, a 21-day neighbour consultation period, and council sign-off — but it is not a full planning application.
Height limit
The eaves of the extension cannot exceed 3 metres if within 2 metres of the boundary. The overall maximum height is 4 metres.
Coverage
The extension (and any other outbuildings) cannot cover more than 50% of the garden area that surrounds the original house.
Two-storey rear extensions
A two-storey rear extension is permitted development only if it projects no more than 3 metres from the original rear wall and is at least 7 metres from the rear boundary. In practice, most South West London terraced houses have relatively short gardens, and the 7-metre rule is often the constraint that pushes a two-storey extension into needing full planning permission.
Even where the size is within the rules, two-storey extensions are more likely to draw objections from neighbours and more likely to be scrutinised carefully by the council. If you're planning a two-storey extension, we'd recommend a pre-application discussion with the council and a more detailed design process before committing to a build.
When you do need planning permission
Conservation areas. Parts of Richmond, Kew, Twickenham Green, Ham, and several other SW London neighbourhoods are designated conservation areas. Within these areas, permitted development rights for extensions are restricted. Any extension that would be visible from a public road or footpath — even a rear extension on a corner plot — is likely to need planning permission. Some permitted development rights are removed entirely in certain conservation areas.
Article 4 Directions. These are local council orders that remove specific permitted development rights. Richmond upon Thames Council and Kingston Council have both used Article 4 Directions in parts of their boroughs. You can check whether your property is affected by searching the council's planning portal or asking us — we check this as a matter of course for every enquiry.
Flats and maisonettes. Permitted development rights for extensions apply to houses only. If you live in a converted flat — even if it's on the ground floor of a Victorian terrace — you'll need planning permission for any extension.
Previous extensions. If a previous owner extended the house under permitted development, the depth limits apply cumulatively. A 2-metre extension already built means you only have 1 metre of permitted development depth remaining (for a terraced house). Going further requires planning permission.
Building regulations — always required regardless
Whether or not you need planning permission, every rear extension must comply with building regulations. Building control covers structural safety, thermal performance, fire separation, drainage connections, and electrical works. You'll need a completion certificate at the end — lenders and solicitors ask for it when you sell.
There are two routes: Full Plans (drawings submitted in advance and checked before work starts) or Building Notice (less paperwork upfront, but inspections happen during the build). For a kitchen extension, Full Plans gives you more certainty and is generally the approach we recommend for anything above a basic single-storey structure.
Party wall — a separate legal requirement
If your rear extension involves digging foundations within 3 metres of a neighbour's structure, or if you're building on or against a shared boundary wall, the Party Wall Act 1996 applies. You must serve notice on affected neighbours before work starts. This is a legal requirement — not optional — even if planning permission isn't needed.
Most neighbours consent without issue, particularly if the work is explained clearly and professionally. Distinct Spaces handles party wall notices as part of the pre-construction process on every project where they're required.
Getting certainty: the Lawful Development Certificate
If your extension is permitted development, you can apply to the council for a Lawful Development Certificate confirming it. This costs around £103, takes about 8 weeks, and gives you a formal document proving the extension is lawful. It's particularly useful when selling — it removes any question about whether the extension was built correctly and within the rules.
We routinely obtain LDCs for clients where the extension is clearly permitted development. It's a modest cost that prevents problems at the point of sale.
Not sure what planning rules apply to your property? We can give you a clear answer on your first call.
Get in touch