What Does a Loft Conversion Cost?
Quick Answer
£20,000–£65,000 depending on type (2026 UK)
Velux/rooflight: £20–30K • Dormer: £30–50K • Hip-to-gable: £40–65K
Cost by Conversion Type (2026)
- Velux/rooflight conversion: £20,000–£30,000. No external structural changes, just windows in the existing roof slope
- Rear dormer: £30,000–£50,000. Flat-roof or pitched dormer extending from the rear roof
- Hip-to-gable: £40,000–£55,000. Extends the hipped roof to a vertical gable wall
- Hip-to-gable + rear dormer: £45,000–£65,000. Maximum space, most popular for semis
- Mansard: £50,000–£70,000. Alters the roof profile, usually needs planning permission
What’s Included in Typical Quotes
- Structural steelwork and new floor joists
- Staircase from first floor to loft
- Dormer construction (if applicable)
- Windows (Velux or dormer glazing)
- Insulation, plasterboarding, and plastering
- Electrics (lighting, sockets)
- Fire door upgrades to existing rooms
Extras That Add Cost
- En-suite bathroom: £5,000–£10,000
- Juliet balcony: £1,000–£2,500
- Scaffolding (complex access): £1,500–£3,000
- Party wall agreement: £700–£1,500 per neighbour
- Planning application (if needed): £250–£500
Value Added
A well-executed loft conversion typically adds 15–20% to a property’s value. In many UK areas, this makes it one of the most cost-effective home improvements.
Last updated: April 2026