Basement conversion and construction in Chelsea.
Chelsea · SW3 · Chelsea basement and extensionCompleted work, photograph
New basements and conversions under Chelsea houses, within CD11’s one storey. Designed, engineered and built by one team.
What a Chelsea basement can be.
- CD11, 2024
- One storey, half the garden at most
- Each garden
- Front, rear and side measured separately
- SW3 · SW10
- Terraces, squares and studio houses
NU Projects is a design and build company in Fulham SW6, founded in 2010. We handle basement conversion and construction in Chelsea SW3, under one contract. A new basement dig typically runs £500k to £900k. Converting an existing basement runs £180k to £300k. Call 020 7731 6841, and a budget estimate typically follows within seven days.
Chelsea is terraces and garden squares, with studio houses and riverside streets between them. Most of it is conservation area.
The borough changed basements here in January 2015. The rule, now Policy CD11, allows one storey under half the garden.
So a Chelsea basement is designed to make one storey count. Height, light and where the plant goes are settled early.
We built a new basement and a kitchen extension in Chelsea, under one contract. One team ran the structure, the design and the fit-out.
What the council allows in Chelsea.
- Council
- Royal Borough of Kensington and Chelsea. Chelsea sits wholly inside it.
- Policy CD11
- Adopted as CL7 in January 2015, kept in the 2024 Local Plan. One storey, under half the garden.
- Basements SPD
- Adopted April 2016. The storey cannot be split in two later. A pool may earn a little extra depth.
- The garden
- The garden left over must stay as one area. It is usually the end furthest from the house.
- Neighbours
- Considerate Constructors Scheme membership is set by planning condition.
- On site
- A Construction Traffic Management Plan goes in with the application. The Code of Construction Practice, revised 2019, governs the site.
Source: Kensington and Chelsea’s Local Plan 2024, Policies CD4, CD5, CD11 and CD13. Read on 3 October 2026. Policies change, so we read them again for your address.
Basements in the borough.
Chelsea·Townhouse
Chelsea basement and extension
A new basement and a kitchen extension in Chelsea, with the interior renovated throughout.
See the project
Kensington·New build
Kensington new-build houses
Two houses in the same borough, three floors down, consented before CL7.
See the projectCompleted work, photographs
What a basement costs in Chelsea.
£180k to £300kConverting an existing basement. A project total, from our 2026 cost guide.
£500k to £900k+Digging a new basement. A project total, from our 2026 cost guide.
The cost guide figures are whole project totals.
Fees, party wall costs, contingency and VAT sit outside them.
Open the calculatorThe 2026 cost guideBasement costs in full
What Chelsea owners ask about basements.
In Chelsea
- Every service in Chelsea
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- Interior design in Chelsea
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- Party wall surveying in Chelsea
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- Architectural design in Chelsea
- Basement swimming pools in Chelsea
- Basement gyms in Chelsea
- Basement cinema rooms in Chelsea
- Basement golf simulator rooms in Chelsea
- Luxury painting and decorating in Chelsea
Basements nearby
- Basement construction across London
- Basement construction in Fulham
- Basement construction in Kensington
- Basement construction in St John’s Wood
- Basement construction in South Kensington
- Basement construction in Knightsbridge
- Basement construction in Belgravia
- Basement construction in Mayfair
- Basement construction in Marylebone
- Basement construction in Holland Park
- Basement construction in Hampstead
- Basement construction in Notting Hill
- Basement construction in Clapham
- Basement construction in Weybridge
- Basement construction in Cobham
- Basement construction in Oxshott
- Kensington
- South Kensington
- Knightsbridge
Further reading, from the journal
Can I build a double basement in Chelsea?
Not any more. The borough has limited new basements to one storey since 2015.
Our Kensington houses went three floors down, consented before the rule.
Today we design one generous storey instead.
How much of a Chelsea garden can a basement go under?
No more than half of it, under Policy CD11.
The garden left over must stay as one area.
It is usually the end furthest from the house.
What goes in with a Chelsea basement application?
A draft Construction Traffic Management Plan goes in with it.
The final plan follows as a planning condition.
We prepare it with the drawings and the structural design.
Can a Chelsea basement have a pool?
Sometimes. The borough’s 2016 guidance allows a little extra depth for one.
It is still one storey, under half the garden.
We test it against the site before you commit.
What does a Chelsea basement cost?
Our 2026 cost guide puts a new dig at £500k to £900k and more.
Converting an existing cellar runs £180k to £300k as a project total.
Tell us about your home in Chelsea.
Your name and one way to reply are enough. It goes straight to the studio.
- Already have an architect or designer? We build to their design. Working with your designer
- An NDA on request, and your home is never published without your consent. How we work in confidence