Basement construction in Knightsbridge.
Knightsbridge · SW1 · Knightsbridge townhouse, pool and wine roomCompleted work, photograph
Basements in Knightsbridge, on either side of the borough line. We confirm the council first, then design to its rule.
One basement, two rule books.
- Two councils
- Kensington and Chelsea, and Westminster
- One storey
- The limit on both sides of the line
- SW1X · SW7
- Townhouses, mews and mansion blocks
NU Projects is a design and build company in Fulham SW6, founded in 2010. We handle basement conversion and construction in Knightsbridge SW1X, under one contract. A basement runs £450 to £780 a sq ft, construction only. Call 020 7731 6841, and a budget estimate typically follows within seven days.
Knightsbridge is split between Kensington and Chelsea and Westminster. The line runs through the area.
Most homes are mansion block apartments. The townhouses and mews houses are where basements happen.
Both councils now allow one storey below the house. The detail differs, and it matters.
Westminster’s side also has the Knightsbridge Neighbourhood Plan, made in December 2018.
We have completed three homes in Knightsbridge. One townhouse has a pool and a wine room.
What the council allows in Knightsbridge.
- Council
- Kensington and Chelsea to the west and south. Westminster to the east and the park side.
- Kensington and Chelsea
- Policy CD11 of the 2024 Local Plan. One storey, under no more than half the garden.
- Westminster
- City Plan Policy 50. One storey below the lowest original floor, under half the garden.
- Small gardens
- In Westminster, where a garden is 8m or less, a basement may extend 4m.
- Listed houses
- Kensington and Chelsea resists any dig under a listed building. Westminster protects its original order of rooms.
- Under the pavement
- Westminster allows no more than 1.8m under the highway, with 900mm of cover.
Source: Kensington and Chelsea’s Local Plan 2024 Policy CD11, and Westminster’s City Plan Policy 50. Read on 3 October 2026. Policies change, so we read them again for your address.
Below ground, close by.
Knightsbridge·Townhouse
Knightsbridge townhouse, pool and wine room
A Knightsbridge townhouse with a pool and a wine room, built by NU.
See the project
Kensington·New build
Kensington new-build houses
Two new houses we built close by, three floors down, consented before today’s limit.
See the projectCompleted work, photographs
What a basement costs in Knightsbridge.
£450 to £780a sq ft, construction only. Our basement band.
£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.
A mews house and a townhouse price very differently below ground.
The band is per square foot, construction only. The guide figures are project totals.
Fees, party wall costs, contingency and VAT sit outside both.
Open the calculatorThe 2026 cost guideBasement costs in full
What Knightsbridge owners ask about basements.
In Knightsbridge
- Every service in Knightsbridge
- Luxury refurbishment in Knightsbridge
- Interior design in Knightsbridge
- Party wall surveying in Knightsbridge
Basements nearby
- Basement construction across London
- Basement construction in Fulham
- Basement construction in Chelsea
- Basement construction in Kensington
- Basement construction in St John’s Wood
- Basement construction in South Kensington
- Basement construction in Belgravia
- Basement construction in Holland Park
- Basement construction in Hampstead
- Basement construction in Notting Hill
- Basement construction in Clapham
- Belgravia
- South Kensington
- Chelsea
- Mayfair
Further reading, from the journal
Which basement rules apply to my Knightsbridge house?
It depends which side of the borough line the house sits.
Kensington and Chelsea uses Policy CD11. Westminster uses City Plan Policy 50.
We confirm the council from the address before anything is drawn.
Can I dig a basement under a Knightsbridge mews house?
Sometimes. Both councils limit it to one storey.
A mews house often has little garden, so the footprint is tight.
We test it against the right policy at feasibility.
Can a Knightsbridge basement have a swimming pool?
Often, within one storey.
Kensington and Chelsea allows a small extra height for a pool.
Westminster judges the depth against its one storey rule.
Does a Knightsbridge basement need a construction plan?
Yes, on both sides of the line.
Kensington and Chelsea wants a traffic plan and a method statement with the application.
Westminster wants its Code of Construction Practice form signed and submitted.
What does a Knightsbridge basement cost?
Built per square foot, our basement band is £450 to £780.
Our 2026 cost guide puts a new dig at £500k to £900k and more.
Converting a basement you already have runs £180k to £300k in total.
Tell us about your home in Knightsbridge.
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