Typical cost ranges by conversion type
As a broad guide for a standard specification including VAT, most UK loft conversions fall into the ranges below. These figures assume a straightforward property with reasonable access.
- Velux or rooflight conversion: around £28,000 to £45,000
- Dormer conversion: around £42,000 to £70,000
- L-shaped dormer: around £55,000 to £85,000
- Hip-to-gable with rear dormer: around £55,000 to £90,000
- Mansard conversion: around £65,000 to £110,000
What drives the cost up or down
The floor area and the amount of structural work are the two biggest cost drivers. Adding steel beams, moving a water tank, or altering the roof structure all add labour and materials.
Bathrooms and en-suites add plumbing, waterproofing and ventilation. Staircase position can also be significant if it requires alterations to the floor below.
- Floor area and headroom available
- Structural steelwork and floor strengthening
- En-suite or bathroom plumbing
- Staircase design and position
- Quality of finishes, glazing and joinery
- Regional labour rates
Regional differences
London and the South East typically sit 15 to 25 per cent above the national average, while parts of the North, Wales and Scotland can sit below it. Our estimator adjusts for your postcode area automatically.
Costs that are easy to forget
Beyond the build itself, budget for planning or lawful development certificate fees, building control, structural calculations, party wall agreements where relevant, and finishing items such as flooring, blinds and furniture.
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