House Extensions Kensington & Chelsea 2026: Complete Guide to Costs, Planning and Design

The Royal Borough of Kensington and Chelsea is London's most prestigious residential borough and home to some of the most valuable properties in the world. Kensington W8, South Kensington SW7, Chelsea SW3, Fulham SW6, Notting Hill W11 and Holland Park W11 all fall within the borough and offer outstanding opportunities for high-specification house extensions. LCCL Construction delivers house extensions across Kensington and Chelsea and all surrounding areas as part of our complete design and build service.

LCCL Construction — specialist house extension builders in Kensington and Chelsea

House Extensions Kensington and Chelsea: Best Types for Local Properties

Properties in Kensington and Chelsea are predominantly large Victorian and Georgian terraced houses, mansion blocks and townhouses. The best extension type depends on the property style and planning situation. Victorian terraced houses in Chelsea and South Kensington are well suited to rear extensions and basement extensions. Large Victorian terraces in Kensington and Notting Hill suit wraparound extensions and double storey rear extensions. The exceptional property values in the Royal Borough make any well-designed extension an outstanding investment.

How Much Do House Extensions Cost in Kensington and Chelsea in 2026?

House extension costs in Kensington and Chelsea are at the premium end of the London range.

Rear extension: £42,000 – £90,000 inc. VAT (£35,000 – £75,000 + VAT).

Side return extension: £42,000 – £93,600 inc. VAT (£35,000 – £78,000 + VAT).

Wraparound extension: £72,000 – £153,600 inc. VAT (£60,000 – £128,000 + VAT).

Double storey rear extension: £42,000 – £90,000 inc. VAT (£35,000 – £75,000 + VAT).

All costs include architectural design, planning permission, building regulations, structural calculations, party wall agreements, construction and finishing to a high specification. See our full house extension cost guide.

Planning Permission for House Extensions in Kensington and Chelsea

Planning permission in the Royal Borough of Kensington and Chelsea is complex. The borough has one of the highest proportions of conservation area coverage in London — virtually the entire borough is within a conservation area. This means that planning permission is required for almost all house extensions in Kensington and Chelsea, including most single storey rear extensions that would be permitted development elsewhere. LCCL Construction has extensive experience navigating RBKC's planning requirements and handles all planning applications as part of our design and build service. See our full guide to house extension planning permission in London.

Why Is a House Extension Such a Strong Investment in Kensington and Chelsea?

Kensington and Chelsea has the highest average property values of any London borough. A terraced house in Chelsea or South Kensington regularly achieves £2,000,000 to £6,000,000. At these values a rear extension costing £35,000 to £75,000 can add £200,000 to £400,000 to the property value — a return of 200 to 500 per cent on the construction cost. The open plan kitchen diner created by a rear or wraparound extension is consistently the most valued improvement by buyers in the RBKC property market.

Areas of Kensington and Chelsea We Cover

LCCL Construction covers all areas of the Royal Borough of Kensington and Chelsea including Kensington W8, South Kensington SW7, Chelsea SW3, Fulham SW6, Notting Hill W11, Holland Park W11 W14, Earls Court SW5, West Brompton SW10, North Kensington W10, Ladbroke Grove W11 and all surrounding postcodes.

Can it be done under permitted development?

A single-storey rear extension of 3 m on a terrace or semi (4 m on a detached house), a side-return infill and a side extension up to half the original width are permitted development on a house outside a conservation area or Article 4 street — no planning application, just a Lawful Development Certificate, which we apply for on every one. Fixed-price permitted development extensions start from £42,000 inc. VAT (£35,000 + VAT) at economy specification, design and build inclusive, and the 6 m / 8 m larger home extension goes through a 42-day prior approval notification rather than a full application. See our permitted development projects page for every product with its from-price and the checks we run before we confirm a project qualifies. Not sure whether your project needs a planning application? Check if you need planning permission

Frequently Asked Questions About House Extensions in Kensington and Chelsea

Do I need planning permission for a house extension in Kensington and Chelsea?

Almost certainly yes — virtually the entire Royal Borough of Kensington and Chelsea is within a conservation area where planning permission is required for most extensions. LCCL Construction manages all planning applications as part of our design and build service.

To discuss your Kensington or Chelsea extension project call LCCL Construction on 020 8037 7332 or get an instant quote online.