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 Magherafelt?
In Magherafelt, a basement conversion typically costs £1,650–£2,750 per m² for converting an existing cellar, including VAT at 20% (standard rate). For a typical 30 m² project that is roughly £49,500–£82,500. That range is adjusted for Northern Ireland, where domestic building work typically costs around 14% below the national average. Design, structural calculations and council fees are extra.
| Size or type | Guide range |
|---|---|
| Smaller project (21 m²) | £34,500–£58,000 |
| Typical project (30 m²) | £49,500–£82,500 |
| Larger project (42 m²) | £69,500–£115,500 |
| Rate per m² | £1,650–£2,750 |
The biggest cost drivers are:
- Floor lowering and underpinning
- Waterproofing system
- Lightwells
- Ground water and access
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 Magherafelt?
The approval route for Magherafelt is set by planning law in Northern Ireland. In Northern Ireland converting an existing cellar usually does not need planning permission; new excavation and external changes may.
In Northern Ireland building control approval comes from the council, usually through a full plans application or a building notice, with inspections during the work and a completion certificate at the end.
If the answer is not clear-cut, we can apply for formal confirmation before you commit to the build.
What we handle
What we take care of:
- Insulation, ventilation and drainage pumps
- Electrics, heating and plastering
- Waterproofing design (tanking or cavity drain membrane)
- Structural and ground survey
- Building control sign-off
- Underpinning or new structure where needed
How long does it take?
The build itself usually takes 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 Magherafelt
Across Northern Ireland, bungalows and chalet bungalows are common, so loft conversions and rear extensions are popular projects.
Our Magherafelt coverage includes postcode districts BT45, and we also work in nearby places such as Cookstown, Ballymena and Antrim.
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
Approvals in place
We handle planning, building control and neighbour notices before work starts.
- 04
Build and sign-off
We run the build to a written programme and hand over the completion certificate.
Questions about basement conversions in Magherafelt
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 Magherafelt?
Yes. We build basement conversions across Magherafelt, including postcodes BT45. Every project starts with a free home visit.
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 Magherafelt?
In Northern Ireland converting an existing cellar usually does not need planning permission; new excavation and external changes may.
How much does a basement conversion cost in Magherafelt?
In Magherafelt, a basement conversion typically costs £1,650–£2,750 per m² for converting an existing cellar, including VAT at 20% (standard rate). A typical 30 m² project comes to roughly £49,500–£82,500. 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.