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 Limavady?
In Limavady, 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. We start from a UK-wide guide and adjust it for Northern Ireland, where labour and materials are typically about 14% below 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 |
What moves the price most:
- Agreements with neighbours on shared walls
- Ground water and access
- Existing cellar or new excavation
- Waterproofing system
For a figure based on your own measurements, try the guide price tool, then book a free home visit for a fixed quote.
Do you need planning permission for a basement conversion in Limavady?
Before anything is built in Limavady, we confirm which approvals apply in Northern Ireland. In Northern Ireland converting an existing cellar usually does not need planning permission; new excavation and external changes may.
Northern Ireland has no Party Wall Act. Work on shared walls relies on agreement with the neighbour and common law, so we agree the arrangements in writing before work starts.
At the survey we check your house’s planning history and any restrictions, and tell you which route applies.
What we handle
What we take care of:
- Underpinning or new structure where needed
- Insulation, ventilation and drainage pumps
- Electrics, heating and plastering
- Building control sign-off
- Waterproofing design (tanking or cavity drain membrane)
- Written agreement with neighbours on shared walls
How long does it take?
Build time is typically 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 Limavady
Across Northern Ireland, bungalows and chalet bungalows are common, so loft conversions and rear extensions are popular projects.
We work across Limavady and neighbouring areas such as Coleraine, Derry and Magherafelt. Postcodes we cover in Limavady include BT49.
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
Approvals
Planning or permitted development confirmation, building regulations and any party wall matters.
- 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 Limavady
Do I need planning permission for a basement conversion in Limavady?
In Northern Ireland converting an existing cellar usually does not need planning permission; new excavation and external changes may.
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 Limavady?
Typically 8 to 16 weeks for a cellar conversion; longer for new excavation. Design and approvals beforehand usually take 3 to 5 months.
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.
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 Limavady?
In Limavady, 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.