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 Bridgend?
In Bridgend, 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 Bridgend 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 |
What moves the price most:
- Ground water and access
- Floor lowering and underpinning
- Party wall surveyor fees
- Waterproofing system
Use the guide price tool to see how size and specification change the figure, then ask for a written, itemised quote.
Do you need planning permission for a basement conversion in Bridgend?
Approvals for a basement conversion in Bridgend follow the rules for 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
On a typical basement conversion we handle:
- Structural and ground survey
- Party wall notices
- Insulation, ventilation and drainage pumps
- Waterproofing design (tanking or cavity drain membrane)
- Building control sign-off
- Electrics, heating and plastering
How long does it take?
Expect 8 to 16 weeks for a cellar conversion; longer for new excavation. Allow time beforehand for drawings and approvals, usually 3 to 5 months.
Building in Bridgend
Terraced houses in Welsh towns often have narrow plots, which suits rear and side return extensions and rear dormers.
From CF31 outwards, we take on projects throughout Bridgend and the surrounding parts of Mid Glamorgan.
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
Construction and completion
We build, put right any snags and hand over the building control certificate.
Questions about basement conversions in Bridgend
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 Bridgend?
In Wales converting an existing cellar usually does not need planning permission; new excavation and lightwells may.
Is new excavation worth it?
It can be in high-value areas, but costs are high. We give a feasibility view before design starts.
How much does a basement conversion cost in Bridgend?
In Bridgend, 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.
Can a basement be a bedroom?
Yes, with a suitable escape route such as a lightwell window or protected stair.
Do you build basement conversions in Bridgend?
Yes. We build basement conversions across Bridgend, including postcodes CF31. Every project starts with a free home visit.