Calculate your loft conversion
2026 loft conversion costs by type
30m² benchmark · 4–6 weeks£22,500–£30,000
30m² benchmark · 10–12 weeks£40,000–£60,000
30m² benchmark · 10–12 weeks£50,000–£70,000
30m² benchmark · 8–10 weeks£50,000–£80,000
30m² benchmark · 8–10 weeks£22,500–£37,500
50m² benchmark · 10–12 weeks£62,500–£87,500
What each loft conversion type means
Velux / rooflight
Keeps the existing roof shape and adds rooflights.
£27,500 average£22,500–£30,000Dormer
Adds a box-like roof extension for more headroom and usable floor area.
£50,000 average£40,000–£60,000Hip-to-gable
Rebuilds a hipped roof end into a vertical gable wall.
£60,000 average£50,000–£70,000Mansard
Major roof reconstruction creating a steep rear roof slope and substantial space.
£65,000 average£50,000–£80,000Velux vs dormer vs hip-to-gable vs mansard
Velux / rooflight is normally the lowest-cost route where the existing roof already has enough usable height. Dormers are more expensive but create valuable headroom and floor area. Hip-to-gable changes the side roof profile and is common on suitable semis and detached homes. Mansard involves the most extensive roof alteration of these mainstream types and therefore tends to sit at the higher end.
Costs people often miss
- Structural engineer and design fees where required.
- Building Control charges and compliance work.
- Party-wall surveyor costs where the Party Wall etc. Act applies.
- New staircase design, balustrades and alterations to the floor below.
- Bathroom or ensuite plumbing, drainage and ventilation.
- Scaffolding, restricted access and waste removal.
- Decoration, fitted storage, flooring and upgraded electrics.
- Contingency for structural conditions discovered after opening the roof.
Regional loft conversion pricing
The calculator applies the same published UK benchmark through a transparent regional model rather than presenting modelled city figures as observed local quote averages.
Source and methodology
Loft Conversion Cost: 2026 UK Price Guide & Breakdown
Last updated: March 2026
Used for: 30m² Velux, dormer, hip-to-gable, mansard and shell benchmarks plus the 50m² bungalow benchmark.
Size scaling, regional factors and ensuite adjustments in the interactive calculator are UK Home Costs modelling assumptions and are kept separate from the source table. Read the methodology →
Frequently asked questions
How much does a dormer loft conversion cost in 2026?
For a typical 30m² project, Checkatrade’s 2026 table gives £40,000–£60,000, with an average around £50,000.
How much does a Velux loft conversion cost?
A typical 30m² Velux or rooflight conversion is benchmarked at about £22,500–£30,000, averaging around £27,500.
How much does a hip-to-gable loft conversion cost?
A typical 30m² hip-to-gable conversion is benchmarked at about £50,000–£70,000, with an average around £60,000.
How much does a mansard loft conversion cost?
A typical 30m² mansard conversion is benchmarked at about £50,000–£80,000, averaging around £65,000.
Which loft conversion is usually cheapest?
A Velux or rooflight conversion is generally the least expensive because it preserves more of the existing roof structure. Suitability depends on the existing head height and roof form.
Does adding an ensuite increase the loft conversion cost?
Yes. Plumbing, drainage, ventilation, waterproofing, sanitaryware and finishes all add to the project. UK Home Costs models an ensuite separately in the loft calculator.