House Extension Planning Permission London 2026: Complete Guide

Understanding planning permission for a house extension in London is one of the most important steps before starting any extension project. The rules are more complex in London than elsewhere in the UK due to the high number of conservation areas, Article 4 directions and listed buildings across the capital. This guide explains exactly when you do and don't need planning permission for a house extension in London in 2026.

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

Do You Need Planning Permission for a House Extension in London?

Most single storey rear extensions in London can be built under permitted development rights without planning permission, provided they meet specific size and design criteria. However London has over 1,000 conservation areas and many properties across the capital fall within Article 4 directions that remove or restrict permitted development rights. This means it is essential to check your specific property's planning situation before assuming permitted development applies.

Permitted Development Rules for House Extensions in London

Under standard permitted development a single storey rear extension can extend up to 3 metres beyond the original rear wall of a semi-detached or terraced house, or 4 metres for a detached house. The extension must not be higher than 4 metres, must not cover more than 50 per cent of the garden area, must use materials that match the existing house and must not include a veranda or balcony. Side extensions under permitted development can be no wider than half the width of the original house.

The Larger Home Extension Scheme: Extending Further Without Planning Permission

Under the Larger Home Extension Scheme (prior approval) the permitted development limits for single storey rear extensions increase to 6 metres for semi-detached and terraced houses and 8 metres for detached houses. This scheme requires prior approval from the local planning authority, which involves notifying neighbours and allowing 42 days for objections. If no valid objections are received prior approval is granted. This scheme does not apply to conservation areas or flats.

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

Planning permission is always required for: double storey extensions, extensions that exceed the permitted development size limits, side extensions wider than half the width of the original house, any extension on a property in a conservation area, any extension on a listed building, extensions on flats and maisonettes, and extensions that would result in more than 50 per cent of the garden being covered by buildings. In London almost all wraparound extensions require planning permission because the side element exceeds permitted development limits.

Conservation Areas and House Extension Planning Permission in London

London has over 1,000 conservation areas covering significant parts of almost every London borough. Within conservation areas permitted development rights for side extensions and certain rear extensions are removed. Any extension visible from a public highway in a conservation area requires planning permission. Properties in conservation areas can still be extended but all extensions require a planning application, which typically takes 8 to 10 weeks to determine. LCCL Construction checks all conservation area designations as part of our free initial consultation.

How Long Does Planning Permission Take for a House Extension in London?

A standard householder planning application for a house extension in London typically takes 8 to 10 weeks from submission to decision. Complex applications in conservation areas or on listed buildings can take longer. Prior approval under the Larger Home Extension Scheme takes a minimum of 42 days. LCCL Construction prepares and submits all planning applications as part of our design and build service and manages the process on your behalf.

Frequently Asked Questions About House Extension Planning Permission in London

Do I need planning permission for a rear extension in London?

Most single storey rear extensions up to 3 metres (terraced or semi) or 4 metres (detached) do not require planning permission. See our full guide to planning permission for rear extensions.

Do I need planning permission for a wraparound extension in London?

Almost always yes — the side return element typically exceeds permitted development limits for side extensions. LCCL Construction handles all planning applications as part of our design and build service.

How much does planning permission cost for a house extension in London?

A standard householder planning application costs £528 as of April 2025. LCCL Construction includes the preparation and submission of all planning applications in our design and build service.

To get a free consultation including a planning permission check call LCCL Construction on 020 8037 7332 or get an instant quote online.