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 Caldicot?
In Caldicot, 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. Building costs in Wales run about 8% below the UK average, and the figures for Caldicot are adjusted to reflect that. 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:
- Lightwells
- Ground water and access
- Party wall surveyor fees
- Floor lowering and underpinning
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 Caldicot?
Approvals for a basement conversion in Caldicot 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.
At the survey we check your house’s planning history and any restrictions, and tell you which route applies.
What we handle
Handled as part of most basement conversions:
- Party wall notices
- Lightwells and windows
- Building control sign-off
- Insulation, ventilation and drainage pumps
- Underpinning or new structure where needed
- Waterproofing design (tanking or cavity drain membrane)
How long does it take?
Allow 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 Caldicot
Terraced houses in Welsh towns often have narrow plots, which suits rear and side return extensions and rear dormers.
Caldicot sits in Gwent, about 10 miles east of Newport. We cover the whole of Caldicot, including postcodes NP26.
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 handover
Work follows the agreed programme, with inspections along the way and a completion certificate at the end.
Questions about basement conversions in Caldicot
Do you build basement conversions in Caldicot?
Yes. We build basement conversions across Caldicot, including postcodes NP26. Every project starts with a free home visit.
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 long does it take?
A cellar conversion takes around 8 to 16 weeks; new basements take longer.
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.
Do I need planning permission for a basement conversion in Caldicot?
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 Caldicot?
In Caldicot, 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.