Permitted Development Rules: London Extensions 2026

Under standard Permitted Development rights in 2026, a single-storey rear extension can go 3m deep on a terraced or semi-detached house and 4m on a detached one, to a maximum height of 4m. The Neighbour Consultation Scheme extends those depths, and conservation areas and Article 4 Directions remove them. Our extensions page covers what we build under PD, the cost hub prices it by area, and the estimator puts a band on a specific footprint.

Permitted Development rights let you build extensions, loft conversions and outbuildings without a planning application — but the rules are specific and the exceptions matter. Getting this wrong costs time and money. Getting it right means you can start work months earlier.

This guide covers the 2026 position for London homeowners.

What Is Permitted Development?

Permitted Development (PD) is a national planning consent granted by Parliament — not the council. The Town and Country Planning (General Permitted Development) (England) Order 2015 sets out what can be built, and to what size limits, without a planning application.

The key word is “without a planning application.” PD rights exist automatically. You do not apply for them. What you can apply for — and what we strongly recommend — is a Certificate of Lawful Development, which is the council’s written confirmation that your specific project falls within PD.

Rear Extensions: The Rules

Standard Permitted Development limits (single-storey)

Neighbour Consultation Scheme (Prior Approval)

The Neighbour Consultation Scheme extends PD limits for single-storey extensions only:

Under this route, you submit a Prior Approval application to the council (fee: £258). The council notifies your neighbours; if they raise no objection, Prior Approval is confirmed and you can build. If objections are raised, the council assesses the impact on neighbours. This is not a full planning application — the council cannot refuse on design grounds, only on impact on amenity.

Double-storey rear extensions

A double-storey rear extension falls within PD provided:

• Maximum 3m depth from the original rear wall
• At least 7m from the rear boundary
• The upper floor does not include side-facing windows (or they are obscure-glazed and non-opening)
• The roof pitch matches the existing house

Double-storey side extensions do not fall within PD — they require full planning permission.

Side Return Extensions

A side return extension (filling in the passage alongside the ground floor) is treated as a side extension under PD rules. The PD conditions for side extensions are stricter than for rear extensions:

• Must not exceed half the width of the original house
• Must not be forward of the principal elevation (i.e., cannot project toward the street)
• Must be single-storey to use PD (maximum 4m height)
• In conservation areas: side extensions under PD are automatically excluded — you need planning permission

Most London Victorian terraced side returns are 900mm–1.5m wide, which is typically within half the width of the original house. But the exact geometry matters — always confirm with a CLD rather than assuming.

When combined with a rear extension (an L-shape), the rear element follows rear extension rules and the side element follows side extension rules. Both must be within their respective PD limits for the combined project to be PD.

Loft Conversions Under Permitted Development

Loft conversions also fall within PD, subject to volume limits:

Additional conditions:

• No alteration to the roof slope on any elevation that fronts a highway
• Any dormer must be set back at least 20cm from the eaves
• Materials must be similar in appearance to the existing house
• No balcony, verandah or raised platform

These volume limits apply to the total volume added across all loft works — if a previous owner has already added a dormer, the remaining allowance is reduced by that amount.

When Permitted Development Does NOT Apply

PD rights can be restricted or removed entirely in several circumstances:

Conservation areas Certain PD rights are automatically removed in conservation areas. Side extensions, roof cladding and other works visible from the highway require planning permission. Check whether your property is in a conservation area before assuming PD applies.

Article 4 Directions Councils can issue Article 4 Directions to remove specified PD rights in defined areas. In most inner London conservation areas, Article 4 Directions remove the right to add rear dormers, side extensions and in some cases rear extensions without full planning permission.

Listed buildings No PD rights apply to listed buildings (Grade I, II* or II). All works — including internal alterations — require Listed Building Consent in addition to any planning permission.

Flats and maisonettes PD rights for extensions and loft conversions apply only to houses. Flats and maisonettes have no PD rights for these works under Class A or B. Freeholders of purpose-built flats wishing to extend need full planning permission.

Conditions on the original planning permission Some houses were built with planning conditions that specifically remove PD rights. This is common on new developments from the 1980s–2000s. Check the original planning permission for any such conditions.

How to Confirm Your PD Status

The safest route is to apply for a Certificate of Lawful Development before starting work. This gives you:

• Written confirmation that the works are lawful
• Protection on resale (solicitors will ask)
• Comfort for mortgage lenders
• A clear record for building control

Note: From 6 December 2023, the planning application fee for householder applications in England increased to £258. This applies to CLDs, Prior Approval and full householder planning applications alike.

Article 4 Directions in London: Which Boroughs

Article 4 Directions restricting rear extensions, dormers or other works are in place across many inner London boroughs. The following boroughs have significant Article 4 coverage:

• Royal Borough of Kensington and Chelsea — Almost the entire borough is covered by conservation area Article 4 Directions affecting roof works and rear extensions.
• City of Westminster — Extensive conservation area and Article 4 coverage, particularly in Mayfair, Marylebone, Belgravia and Pimlico.
• London Borough of Hammersmith and Fulham — Conservation areas in Fulham, Hammersmith and Shepherd’s Bush have Article 4 Directions for roof works.
• London Borough of Wandsworth — Battersea conservation areas; most of SW11 and SW12 is standard PD.
• London Borough of Richmond — Extensive Article 4 coverage in Kew, Richmond and Twickenham.
• London Borough of Hounslow — Chiswick conservation areas have Article 4 for roof alterations.

Article 4 coverage changes. The definitive check is the council’s planning portal for your specific address — or ask your architect to confirm.

Costs Summary

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Whether your project needs planning or not, we handle the whole process. Use the calculator to get a personalised estimate for your extension — then call us to discuss the planning position for your specific address.

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Call us on 020 8050 8968 — we serve Fulham, Chelsea, Battersea, Chiswick, Kensington and across West London.