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 Portadown?
In Portadown, 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. The guide for Portadown reflects typical costs in Northern Ireland, roughly 14% below the UK-wide figure. 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 |
Your quote will depend mainly on:
- Lightwells
- Floor lowering and underpinning
- Existing cellar or new excavation
- Agreements with neighbours on shared walls
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 Portadown?
The approval route for Portadown 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.
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.
If the answer is not clear-cut, we can apply for formal confirmation before you commit to the build.
What we handle
On a typical basement conversion we handle:
- Electrics, heating and plastering
- Building control sign-off
- Insulation, ventilation and drainage pumps
- Structural and ground survey
- Lightwells and windows
- Underpinning or new structure where needed
How long does it take?
Build time is typically 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 Portadown
Across Northern Ireland, bungalows and chalet bungalows are common, so loft conversions and rear extensions are popular projects.
Projects in Portadown (BT62 and BT63) are surveyed in person before we quote, so the price reflects your actual property.
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 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 sign-off
We run the build to a written programme and hand over the completion certificate.
Questions about basement conversions in Portadown
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 Portadown?
In Northern Ireland converting an existing cellar usually does not need planning permission; new excavation and external changes 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.
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 Portadown?
In Portadown, 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.
Who approves a basement conversion in Portadown?
Planning matters in Portadown go to the council covering your address, and the work needs building control approval. We prepare and submit the applications for you.