Loft Conversion Costs UK 2026
Velux, dormer and mansard conversions compared, with realistic total costs.
6 min read · Updated 2026
Key takeaways
- ›A Velux (rooflight) conversion is the most affordable, from £25,000–£35,000.
- ›A dormer loft conversion typically costs £35,000–£55,000.
- ›Mansard and hip-to-gable conversions run £50,000–£70,000+.
Types of conversion
A Velux conversion keeps the existing roof shape and adds rooflights — the least disruptive and cheapest option, but limited headroom. A dormer extends the roof with a vertical window box, adding real usable floorspace. A mansard alters the roof slope on one or both sides for maximum space and is common in terraced London streets. A hip-to-gable extends a hipped roof into a gable to create more room.
Typical price ranges (UK 2026)
- •Velux / rooflight conversion: £25,000–£35,000.
- •Dormer loft conversion: £35,000–£55,000.
- •Hip-to-gable conversion: £40,000–£55,000.
- •Mansard conversion: £50,000–£70,000+.
- •Staircase, electrics, plumbing, decoration usually included; add £5,000–£10,000 for an en-suite.
Permissions and extras
Many loft conversions fall under Permitted Development, but you still need Building Regulations approval. A Party Wall agreement may be needed in a terraced or semi-detached house. Budget for a fixed staircase (not a fold-down ladder) if you want the room to count as proper habitable space, and for an en-suite if you want one — plumbing to a roof is not cheap.
Frequently asked
Does a loft conversion add value?
A well-built loft conversion with a proper staircase and an en-suite is one of the best-value extensions, often adding more value than it costs in the right area.
Related guides
Kitchen Renovation Costs UK 2026
What a new kitchen really costs, from budget flat-pack to a full bespoke fit-out.
Bathroom Renovation Costs UK 2026
From a simple suite swap to a full wet-room conversion, with realistic price ranges.
House Extension Costs UK 2026
Single-storey, double-storey and wrap-around extensions with realistic per-square-metre costs.
Need a tradesperson for this?
Find vetted local tradespeople or post your job for free.