House Extensions Chelsea

A row of red brick riverside townhouses with black railings along the Thames.

Having the Beams team on hand to manage the project and provide extra reassurance on build decisions was incredibly helpful and made the whole experience stress free.

Kerry

London

They have been extremely efficient and reassuring. It was a complex project but they took it all in their stride. They recommended very good contractors who were all punctual, polite and capable.

Andrew

London

All about trust. I felt comfortable with my money, my project, and my home knowing that the outcome would be to my satisfaction or would be made good.

Chris

London

Chelsea extension builders who design and build

Many Chelsea terraces around King's Road and the surrounding streets have side-return potential, while properties closer to Chelsea Embankment can suit a rear or wraparound extension. Our in-house designers plan the project to suit the property and any planning constraints, then a vetted builder delivers it, with one team responsible for design and build.

Types of house extension we build

Side-return, rear, wraparound and double-storey extensions, plus basement-linked schemes where a garden level is dug down as part of the same project. We design each one to fit the property and how you use the space, not a standard template.

What a house extension costs in Chelsea

Chelsea sits at the premium end of the London market, and extension costs reflect that. Based on Beams estimates for London extension projects, typical fixed-price ranges look like this.

Extension type	Typical estimate
Side-return extension	£80,000 - £150,000
Rear extension	£90,000 - £170,000
Wraparound extension	£130,000 - £220,000
Double-storey extension	£180,000 - £350,000+

Your fixed price is agreed after the design stage, once the scope of works is fully specified.

Planning permission for extensions in Chelsea

Nearly three quarters of the Royal Borough of Kensington and Chelsea is covered by one of its 38 conservation areas, and much of Chelsea falls within these boundaries. Some conservation areas in the borough also have Article 4 directions removing permitted development rights, meaning even changes that would normally be permitted development elsewhere may need a full planning application here. We check your property's specific planning position, including any Article 4 direction, before finalising a design.

1. Free estimate and design call

1. Design — we plan your extension and handle the planning position.

2. Fixed price — a vetted builder quotes against the finished design.

3. Build — milestone payments and a 12-month workmanship warranty.

Why an extension is worth it

An extension adds usable space without the cost and disruption of moving, and can reconfigure how a home works day to day, opening up a kitchen, adding a family room, or creating space for a growing household.

Extending a home in Chelsea

Chelsea covers postcodes SW3, SW10 and parts of SW1, from King's Road and Sloane Square through to Cheyne Walk and Chelsea Harbour. The average property price across the Royal Borough of Kensington and Chelsea reached £1,233,000 in the year to July 2026 (provisional, ONS/HM Land Registry), and with much of the borough sitting within a conservation area, we design extensions that fit both the property and the planning constraints that come with it.