Basement construction in Cobham.
Chelsea · SW3 · Chelsea basement and extensionCompleted work, photograph
Cobham sits in Elmbridge, which has no basement policy of its own. We design, price and build the whole basement.
What a Cobham basement has to answer.
- No basement SPD
- Elmbridge judges a basement as an extension
- DM18, April 2015
- Green Belt plots allow a hidden basement
- KT11
- Large plots, mature trees and the Mole valley
NU Projects is a design and build company in Fulham SW6, founded in 2010. We handle basement conversion and construction in Cobham KT11, 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.
Cobham is mostly large detached houses on generous plots. Many sit among mature trees and some stand behind gates. A basement adds a floor without taking any lawn. It also leaves the front of the house as it is.
Elmbridge has no basement policy and no basement SPD. It asks for no impact assessment and sets no depth or garden limit. Outside the Green Belt a basement is judged as an extension. The council weighs design, neighbours, trees and drainage.
Two rivers and the Green Belt set the real limits. The Mole and the Rythe feed the flood zones. Zone 3b allows no basement at all. Elsewhere groundwater is read first, and a hydrology report may follow.
Parts of Cobham are Green Belt, where a basement must stay wholly underground. Our nearest basements are in Chelsea and Fulham. One team designs, prices and builds the work.
What the council allows in Cobham.
- Council
- Elmbridge Borough Council. No basement policy, SPD or impact assessment.
- Green Belt
- Policy DM18, April 2015. Wholly underground, within the footprint, discreet lightwells only.
- Flood zones
- Zone 3b bars basements. Groundwater risk brings a hydrology report.
- Conservation areas
- Cobham, 31 July 1973. Plough Corner, 28 November 1990.
- Article 4
- Two in Cobham cover gates, fences, walls and temporary buildings.
Source: Elmbridge Development Management Plan 2015, Policy DM18, and Flood Risk SPD 2016. Read on 12 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 kitchen extension in Chelsea.
See the project
Fulham·Basements
Fulham basements
A tall basement sitting room in Fulham.
See the projectCompleted work, photographs
What a basement costs in Cobham.
£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.
These are two kinds of figure. The band is a rate per square foot, construction only.
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 Cobham owners ask about basements.
In Cobham
- Every service in Weybridge, Cobham and Oxshott
- Basement swimming pools in Cobham
- Basement gyms in Cobham
- Basement cinema rooms in Cobham
- Basement golf simulator rooms in Cobham
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 Knightsbridge
- Basement construction in Belgravia
- 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 Oxshott
- Wimbledon
- Richmond, Twickenham and East Sheen
Further reading, from the journal
Does a Cobham basement need a basement impact assessment?
Not from Elmbridge, which asks for none.
The council has no basement SPD.
It still judges the design, trees, neighbours and drainage.
Can I build a basement under a Cobham house in the Green Belt?
Yes, if it is wholly underground and inside the existing footprint.
Only discreet lightwells, vents or escape may show.
Anything more counts toward the 25% extension cap.
How does flood risk change a Cobham basement?
Zone 3b allows no basement.
In Zones 2 and 3a a basement may be considered.
Bedrooms and self-contained basements are not allowed there.
What does a basement in Cobham cost?
Our basement band is £450 to £780 a sq ft, construction only.
We price your house, not a template.
Do Cobham conservation areas affect a new basement?
Cobham and Plough Corner are both conservation areas.
Trees there need notice to the council before work.
Heritage policy also weighs how the house looks.
Tell us about your home in Cobham.
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