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 Clydach?
In Clydach, 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. Prices across Wales are typically 8% below the UK average for this kind of work, which is reflected in the range for Clydach. 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 biggest cost drivers are:
- Party wall surveyor fees
- Waterproofing system
- Ground water and access
- Lightwells
Your exact price depends on the survey and drawings. The guide price tool gives a quick range in the meantime.
Do you need planning permission for a basement conversion in Clydach?
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.
Our first visit includes a check of your planning history, so you know the route before paying for drawings.
What we handle
The work we manage on a basement conversion:
- Structural and ground survey
- Underpinning or new structure where needed
- Waterproofing design (tanking or cavity drain membrane)
- Insulation, ventilation and drainage pumps
- Party wall notices
- Lightwells and windows
How long does it take?
Expect 8 to 16 weeks for a cellar conversion; longer for new excavation. Design and approvals come first and typically take 3 to 5 months, depending on the approval route.
Building in Clydach
Terraced houses in Welsh towns often have narrow plots, which suits rear and side return extensions and rear dormers.
Clydach sits in West Glamorgan, about 5 miles north-east of Swansea. We cover the whole of Clydach, including postcodes SA6.
How it works
- 01
Visit and measured survey
A free visit to understand the project, check access and take measurements.
- 02
Design and pricing
Design options, then a fixed quote based on the chosen drawings and specification.
- 03
Permissions sorted
Applications, building control and neighbour arrangements, all before the start date.
- 04
Build and sign-off
We run the build to a written programme and hand over the completion certificate.
Questions about basement conversions in Clydach
How long does it take?
A cellar conversion takes around 8 to 16 weeks; new basements take longer.
Do I need planning permission for a basement conversion in Clydach?
In Wales converting an existing cellar usually does not need planning permission; new excavation and lightwells may.
How much does a basement conversion cost in Clydach?
In Clydach, 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 Clydach?
Planning matters in Clydach go to the council covering your address, and the work needs building control approval. We prepare and submit the applications for you.
Can a basement be a bedroom?
Yes, with a suitable escape route such as a lightwell window or protected stair.