Do I Need Planning Permission for a Rear Extension in London?

One of the most common questions homeowners ask when considering a rear extension in London is whether they need planning permission. The good news is that most single-storey rear extensions can be built without a full planning application under permitted development rights. However, the rules have specific limits and there are important exceptions that apply to many London properties.

LCCL Construction handles all planning permission applications as part of our design and build service

LCCL Construction handles all planning permission assessments and applications as part of our design and build service. This guide explains exactly when you need planning permission for a rear extension in London and when you don't.

What Are Permitted Development Rights?

Permitted development rights allow homeowners to carry out certain types of building work without needing to apply for planning permission. The rules are set by the government and apply across England. For rear extensions, permitted development rights allow you to extend your home up to a certain size without going through the full planning process, saving time and money.

It is important to understand that permitted development rights can be restricted or removed entirely in certain circumstances. LCCL Construction checks permitted development eligibility for every project during our free initial consultation.

Permitted Development Rules for Rear Extensions in London

Under permitted development rights, a single-storey rear extension can be built without planning permission provided it meets all of the following criteria:

Maximum depth: The extension must not extend more than 3 metres beyond the rear wall of the original house if the property is semi-detached or terraced, or 4 metres if the property is detached. Under the Neighbour Consultation Scheme, these limits can be extended to 6 metres for semi-detached and terraced houses and 8 metres for detached houses, subject to neighbour consultation.

Maximum height: The extension must not exceed 4 metres in height. If the extension is within 2 metres of a boundary, the eaves height must not exceed 3 metres.

Materials: The materials used must be similar in appearance to the existing house.

Coverage: The total area covered by extensions and outbuildings must not exceed 50% of the total area of the original garden.

When Do You Need Planning Permission for a Rear Extension in London?

Planning permission will always be required in the following circumstances:

Conservation areas and Article 4 Directions: If your property is in a conservation area, permitted development rights for rear extensions are restricted. Any extension that would be visible from a highway requires planning permission. Many areas of North and Central London fall within conservation areas, including parts of Barnet, Islington, Camden, Hampstead and Muswell Hill.

Listed buildings: If your property is a listed building, permitted development rights do not apply and listed building consent is required in addition to planning permission for any extension.

Exceeding size limits: If your proposed extension exceeds the permitted development size limits outlined above, a full planning application is required.

Flats and maisonettes: Permitted development rights do not apply to flats or maisonettes. Any extension to a flat requires planning permission.

Previous permitted development used: If permitted development rights have already been used on the property, the remaining allowance may be reduced or exhausted.

What Is the Neighbour Consultation Scheme?

The Neighbour Consultation Scheme, sometimes called the Prior Approval process, allows householders to build larger single-storey rear extensions under permitted development — up to 6 metres for terraced and semi-detached houses and 8 metres for detached houses. To use this, you must notify the local authority who will then consult your neighbours. If no objections are received within 42 days, the extension can proceed.

LCCL Construction manages the Neighbour Consultation Scheme application process for all projects where it applies, as part of our full design and build service.

Should I Get a Lawful Development Certificate?

Even when planning permission is not required, it is strongly advisable to apply for a Lawful Development Certificate from your local authority. This is an official document confirming that your extension is lawful and complies with permitted development rules. It protects you when selling the property and gives your solicitor, buyer and mortgage lender confidence that the extension was built correctly.

How Long Does Planning Permission Take for a Rear Extension?

A standard householder planning application typically takes 8 weeks from submission to decision. In some London boroughs, this can take up to 12 weeks. The Neighbour Consultation Scheme takes a minimum of 42 days. LCCL Construction submits all applications as early as possible and runs the planning stage simultaneously with the design stage where possible to reduce the overall project timeline. For more detail see our guide on how long planning permission takes in London.

Do I Need Building Regulations for a Rear Extension?

Yes — building regulations approval is always required for a rear extension regardless of whether planning permission is needed. Building regulations cover structural safety, fire safety, energy efficiency, ventilation and drainage. LCCL Construction handles all building regulations applications and inspections. See our full guide on building regulations for house extensions.

How LCCL Construction Handles Planning for Your Rear Extension

As a design and build company based in Finchley, North London, LCCL Construction manages the entire planning process for your rear house extension from start to finish. We assess permitted development eligibility, prepare and submit all planning applications, liaise with the local authority and handle the Neighbour Consultation Scheme where applicable.

We have over 20 years of experience working with planning authorities across London and Hertfordshire, including conservation areas and sensitive locations. Our LABC Award 2024 for Best Residential Project reflects the quality and compliance of every project we deliver.

To find out whether your rear extension needs planning permission and get a detailed cost estimate, call us on 020 8037 7332 or book a free consultation online.