What is a basement conversion?
A basement conversion turns an existing cellar into living space, or excavates a new basement under the house or garden. Waterproofing, structural support and daylight are the main design challenges.
How much does a basement conversion cost in Dyfed?
In Dyfed, a basement conversion typically costs £1,750–£2,950 per m² for converting an existing cellar, including VAT at 20% (standard rate). For a typical 30 m² project that is roughly £52,500–£88,500. The guide for Dyfed reflects typical costs in Wales, roughly 8% below the UK-wide figure. Design, structural calculations and council fees are extra.
| Size or type | Guide range |
|---|---|
| Smaller project (21 m²) | £37,000–£62,000 |
| Typical project (30 m²) | £52,500–£88,500 |
| Larger project (42 m²) | £73,500–£124,000 |
| Rate per m² | £1,750–£2,950 |
The main things that change the cost:
- Existing cellar or new excavation
- Party wall surveyor fees
- Ground water and access
- Lightwells
For a figure based on your own measurements, try the guide price tool, then book a free home visit for a fixed quote.
Do you need planning permission for a basement conversion in Dyfed?
Here is how the rules work for a basement conversion in Wales. In Wales converting an existing cellar usually does not need planning permission; new excavation and lightwells may.
The Party Wall etc. Act 1996 applies in Wales, so notices must be served before work on a shared wall, on the boundary, or excavation close to a neighbour’s foundations.
If the answer is not clear-cut, we can apply for formal confirmation before you commit to the build.
What we handle
Handled as part of most basement conversions:
- Lightwells and windows
- Building control sign-off
- Electrics, heating and plastering
- Insulation, ventilation and drainage pumps
- Structural and ground survey
- Party wall notices
How long does it take?
Build time is typically 8 to 16 weeks for a cellar conversion; longer for new excavation. Before that, surveys, drawings and approvals usually take 3 to 5 months, longer if the council asks for changes.
Building in Dyfed
Terraced houses in Welsh towns often have narrow plots, which suits rear and side return extensions and rear dormers.
Towns we cover in Dyfed include Llanelli, Ammanford, Aberystwyth, Carmarthen, Haverfordwest and Milford Haven.
How it works
- 01
Visit and measured survey
A free visit to understand the project, check access and take measurements.
- 02
Design and fixed quote
Drawings, structural calculations and an itemised, fixed price for the agreed specification.
- 03
Permissions sorted
Applications, building control and neighbour arrangements, all before the start date.
- 04
Build and handover
Work follows the agreed programme, with inspections along the way and a completion certificate at the end.
Questions about basement conversions in Dyfed
How long does it take?
A cellar conversion takes around 8 to 16 weeks; new basements take longer.
Can a basement be a bedroom?
Yes, with a suitable escape route such as a lightwell window or protected stair.
How much does a basement conversion cost in Dyfed?
In Dyfed, a basement conversion typically costs £1,750–£2,950 per m² for converting an existing cellar, including VAT at 20% (standard rate). A typical 30 m² project comes to roughly £52,500–£88,500. Your fixed price depends on the survey and drawings.
How do you keep a basement dry?
With a waterproofing system designed to BS 8102, typically a cavity drain membrane with a sump pump, or a tanking system.
Who approves a basement conversion in Dyfed?
Planning matters in Dyfed go to the council covering your address, and the work needs building control approval. We prepare and submit the applications for you.
Do I need planning permission for a basement conversion in Dyfed?
In Wales converting an existing cellar usually does not need planning permission; new excavation and lightwells may.