Basement and cellar conversions in South Glamorgan

Covering South Glamorgan

Our basement and cellar conversions service in South Glamorgan covers Cardiff, Barry, Penarth and Llantwit Major and more.

Homes in South Glamorgan

Housing in Wales ranges from terraced streets in the valleys and older industrial towns to stone-built homes in rural areas and modern estates around the cities.

What do you get with a basement conversion?

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.

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

What will a basement conversion cost?

Use these ranges to budget for basement and cellar conversions; the survey turns them into a fixed price for the agreed specification.

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

Do you need permission for a basement conversion in South Glamorgan?

In Wales the planning rules, including what counts as permitted development, are set by the Welsh Government, and Welsh building regulations differ in places from England’s. We check both against your house before drawings are finalised, and handle party wall notices where needed.

In Wales an existing cellar conversion usually does not need planning permission; new excavation and lightwells may.

What should South Glamorgan homeowners check first?

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 are the steps?

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.
Design and fixed price. You get drawings and a written price for the agreed specification before anything is ordered.
Build and hand over. Our teams build to the programme, building control inspects, and you get the completion paperwork at the end.

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.

Do you work in South Glamorgan?

Yes. South Glamorgan is within our coverage for basement and cellar conversions, along with nearby Cardiff and Barry.

Basement and cellar conversions near South Glamorgan

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