Basement and cellar conversions in New Malden

Covering New Malden

Alongside New Malden, we also cover Surbiton, Morden (3 miles to the east) and Wimbledon.

Homes in London

London projects often mean working on period terraces with neighbours on both sides, tight access through the house and conservation area controls, so careful planning and party wall work matter as much as the build.

What is a basement conversion?

Everything below ground depends on keeping water out. We design the waterproofing system (usually a cavity drain membrane with a pump, or tanking) to the relevant British Standard guidance, then add insulation, ventilation, light and an escape route. New basements involve underpinning and a party wall process and are designed with a structural engineer.

Waterproofing design and installation
Underpinning or lowering the floor where needed
Finished floors, walls and ceilings

What is the guide price for a basement conversion in New Malden?

Indicative costs for basement and cellar conversions. London and the South East usually sit towards the top of each range.

Basement and cellar conversions	Guide price incl. VAT
Existing cellar conversion	£1,900 to £3,000 per m²
New basement excavation	£4,200 to £6,600 per m²

How is a basement conversion approved in New Malden?

English projects need planning clearance from the local council, building regulations sign-off from building control, and party wall notices where the work is on or near a shared boundary. We prepare and manage all three.

Converting an existing cellar with no external changes usually does not need planning permission in England. Digging a new basement or adding a lightwell often does, and many councils have basement policies.

What should I think about before starting?

A pump for the drainage system needs a battery back-up.
Headroom of about 2.1 m or more is needed, which may mean lowering the floor.

What happens after I enquire?

Start with a conversation. A short call or the online form is enough for us to understand what you want to build.
Survey at your house. We look at the existing structure, services and access, and agree what the design needs to achieve.
Price and paperwork. The design is priced line by line, and we submit the planning and building control applications.
Build and hand over. Our teams build to the programme, building control inspects, and you get the completion paperwork at the end.

Questions about a basement conversion in New Malden

How much does a basement conversion cost?

Converting an existing cellar costs about £1,900 to £3,000 per square metre including VAT. A new excavated basement is around £4,200 to £6,600 per square metre.

Does a cellar conversion need planning permission?

Usually not if nothing changes outside. New basements and lightwells often do.

How do I get a price for basement and cellar conversions in New Malden?

Use the guide price tool for a ballpark figure, then book a visit for a fixed written price for the agreed specification.

Basement and cellar conversions near New Malden

Learn more about basement and cellar conversions, or see every project we cover in New Malden.