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
Kensington extension builders who design and build
Extending a Kensington home, whether a stucco terrace near Holland Park or a period conversion in Earls Court, means working within some of London's tightest planning rules. Beams handles design, planning and build in one place: our in-house designers draw up the scheme, a vetted builder delivers it, and the price is fixed before work starts.
Types of house extension we build
Side-return extension: Infilling the side alley alongside a period terrace, common across Kensington's Victorian streets.
Rear extension: Extending into the garden to open up the kitchen or living space.
Wraparound extension: Combining side-return and rear for the largest single-storey option.
Double-storey extension: Adding space on both the ground and first floor in one project.
What a house extension costs in Kensington
There is no flat rate. What a house extension costs in Kensington depends on the footprint, whether it is single or double storey, the specification and the condition of the existing structure. Kensington is one of London's most expensive property markets, with the Royal Borough of Kensington and Chelsea recording an average house price of around £1,233,000 in the year to July 2026 (ONS and HM Land Registry, provisional), so extension costs here tend to sit toward the top of the London range.
Project size | Typical estimate |
|---|---|
Lower end | £70,000 |
Most projects | £120,000 |
Larger or higher spec | £195,000 |
Top 10% of projects | £310,000 |
Based on Beams estimates for London house extension projects, these figures are a general guide rather than a fixed quote. A straightforward single-storey side-return sits at the lower end, while a double-storey wraparound with a high-end specification sits higher. Your builder confirms a fixed price once the design and scope are agreed.
Planning permission for extensions in Kensington
Kensington has some of the most extensive conservation area coverage in London: the Royal Borough of Kensington and Chelsea protects 38 conservation areas covering nearly three-quarters of the borough, taking in Holland Park, South Kensington, much of Notting Hill and the streets around Kensington High Street. Many of these areas also carry Article 4 directions, which remove permitted development rights that would otherwise let you build a modest single-storey rear extension without planning permission. In practice, this means most extensions in Kensington need a full planning application to RBKC, even where the same project might not elsewhere in London. Our designers check your address and the applicable planning position before drawing up a scheme, so you are not designing towards something that will not be approved.
Our design and build process
1. Design and planning: Our team designs your extension and, where needed, prepares and submits the planning application.
2. Fixed-price build: A vetted builder delivers the project under one fixed-price contract with milestone payments.
3. Sign-off: Building control sign-off and a 12-month workmanship warranty on completion.
Why an extension is worth it
Moving house in Kensington means competing in one of London's most expensive markets, with an average price of around £1,233,000 across the borough. Extending is often the more cost-effective way to get the extra space and better layout you need, particularly a side-return or rear extension that opens up the kitchen and living area, without the cost and disruption of moving.
Extending a home in Kensington
Kensington's housing stock, from the grand stucco terraces of Holland Park and South Kensington to the smaller conversions of Earls Court and West Kensington, sets the shape of what an extension can achieve. Side-return and rear extensions on period terraces are the most common projects, opening up dark, narrow kitchens into brighter, larger family spaces. With most of the borough inside a conservation area and much of it also covered by Article 4 directions, getting the planning strategy right from the outset matters as much as the design itself. Our team handles both, working alongside vetted builders across Kensington and neighbouring Chelsea, Hammersmith and Fulham.
Other services in Kensington
We also help Kensington homeowners with:
Basement conversion in Kensington
Bathroom renovation in Kensington
Kitchen renovation in Kensington
House extensions in nearby areas:
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