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 Aberystwyth?
In Aberystwyth, 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 Aberystwyth 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 |
The biggest cost drivers are:
- Ground water and access
- Existing cellar or new excavation
- Lightwells
- 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 Aberystwyth?
The approval route for Aberystwyth is set by planning law in Wales. In Wales converting an existing cellar usually does not need planning permission; new excavation and lightwells may.
Building regulations in Wales are set by the Welsh Government. Approval comes from the council’s building control service or a registered building control approver, with inspections during the work and a completion certificate at the end.
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:
- Building control sign-off
- Insulation, ventilation and drainage pumps
- Electrics, heating and plastering
- Underpinning or new structure where needed
- Lightwells and windows
- Party wall notices
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 Aberystwyth
Wales has many terraced valley streets, stone cottages and post-war estates, so extension designs are shaped by slopes, materials and local character.
From SY23 outwards, we take on projects throughout Aberystwyth and the surrounding parts of Dyfed.
How it works
- 01
Survey and brief
We visit, discuss your ideas and budget, and survey the property or site at no cost.
- 02
Design and fixed quote
Drawings, structural calculations and an itemised, fixed price for the agreed specification.
- 03
Approvals
Planning or permitted development confirmation, building regulations and any party wall matters.
- 04
Build and sign-off
We run the build to a written programme and hand over the completion certificate.
Questions about basement conversions in Aberystwyth
How much does a basement conversion cost in Aberystwyth?
In Aberystwyth, 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.
How long does a basement conversion take in Aberystwyth?
Typically 8 to 16 weeks for a cellar conversion; longer for new excavation. Design and approvals beforehand usually take 3 to 5 months.
Is new excavation worth it?
It can be in high-value areas, but costs are high. We give a feasibility view before design starts.
Do I need planning permission for a basement conversion in Aberystwyth?
In Wales converting an existing cellar usually does not need planning permission; new excavation and lightwells may.
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.