Calculate your loft conversion cost
Loft conversion cost by type in Belfast
The national source benchmarks below are for typical 30m² projects. The Belfast column applies the same 0.89× regional model to each type.
UK £22,500–£30,000£20,050–£26,700
UK £40,000–£60,000£35,600–£53,400
UK £50,000–£70,000£44,500–£62,300
UK £50,000–£80,000£44,500–£71,200
What the regional adjustment changes
What can change a real Belfast quote?
- Velux, dormer, hip-to-gable, mansard or shell-only type
- Usable new floor area
- Roof structure and existing head height
- New staircase position and specification
- Structural steel and roof alterations
- Ensuite, electrics, heating and finish level
- Region, access and scaffolding
Local planning considerations
Northern Ireland has different policy and grant arrangements from Great Britain, so scheme-specific calculator assumptions should be checked carefully.
- Northern Ireland regulations, approvals and support schemes should be checked independently from England, Wales and Scotland guidance.
- Regional material supply, specialist-trade availability and travel can affect individual quotes beyond the broad model factor.
- For major refurbishment, keep surveys, remedial work and compliance costs separate from visible finish upgrades.
How the regional model works
The 0.89× factor places this planning estimate 11% below the national planning baseline. We keep that modelling assumption separate from the dated national benchmark so users can see exactly which part comes from an external source and which part is UK Home Costs modelling.
Sources
Loft Conversion Cost: 2026 UK Price Guide & Breakdown
Published / checked: March 2026
Used for: Loft conversion type benchmarks
Construction output price indices
Published / checked: 13 August 2026
Used for: Construction price trend and update checks
Frequently asked questions
How much does a loft conversion cost in Belfast in 2026?
Our modelled Belfast ranges run from about £20,050–£26,700 for a 30m² Velux or rooflight conversion to about £44,500–£71,200 for a 30m² mansard, using current national type benchmarks and the Northern Ireland regional factor.
How much is a dormer loft conversion in Belfast?
The modelled Belfast planning range for a typical 30m² dormer is about £35,600–£53,400. It starts from the current national £40,000–£60,000 benchmark and applies the Northern Ireland factor.
Why is the Belfast estimate different from the UK benchmark?
UK Home Costs applies a 0.89× Northern Ireland planning factor, which places the model 11% below the national planning baseline. The factor is a transparent modelling assumption and not an observed city-wide contractor price index.
What can push a loft conversion above the modelled range?
Staircase changes, structural steel, low head height, complex roof alterations, an ensuite, premium finishes, difficult access and fire-safety work can all increase the final quote.