Basement and cellar conversions in Cornwall

Covering Cornwall

We cover Cornwall, including Redruth, Falmouth, St Austell and Truro, and the towns around them.

Projects in Cornwall are taken on by arrangement, and any travel and accommodation costs for the team are shown openly in the quote.

Homes in the South West

In the South West, matching local stone, render or slate is often the main design question, and conservation areas and listed buildings are common in historic towns.

What is included in a basement conversion in Cornwall?

A basement conversion turns an existing cellar into dry, usable rooms, or excavates a new basement under a house. Converting an existing cellar is far simpler and cheaper than digging a new one, and often does not need planning permission.

Damp and structural survey
Waterproofing design and installation
Ventilation, heating and electrics

How much should I budget for a basement conversion?

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

Planning and building rules in Cornwall

Projects in England go through two separate checks. Planning (or confirmation that the work is permitted development) comes from the district, borough or unitary council, and building regulations approval comes from the council’s building control team or a registered building control approver. Where work touches a shared wall or digs near a neighbour’s foundations, the Party Wall etc. Act 1996 applies.

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 Cornwall homeowners check first?

New basements nearly always involve the Party Wall Act in England and Wales.
Headroom of about 2.1 m or more is needed, which may mean lowering the floor.

What happens after I enquire?

Tell us about the project. Call, use the guide price tool or send the form with a few photos and a postcode.
We visit and measure. A surveyor checks the house, the boundaries and the ground, and discusses what is realistic.
Price and paperwork. The design is priced line by line, and we submit the planning and building control applications.
We build it. Work follows an agreed programme, with inspections at each stage and a final sign-off.

Your questions answered

Does a cellar conversion need planning permission?

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

How do you keep a basement dry?

With a designed waterproofing system, usually a cavity drain membrane draining to a pump, sometimes combined with tanking.

Can you visit a house in Cornwall to quote?

Yes. After a short call we arrange a site visit to measure up and agree what the design needs to do, then send a written price.

Basement and cellar conversions near Cornwall

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