UK · Price guide
How Much Does a Loft Conversion Cost in the UK?
Typical range
£27,500 — £75,000
Most UK loft conversions cost about £27,500 to £75,000. A simple rooflight conversion sits near the low end, while dormer and hip-to-gable work with complex structure or an en-suite moves toward the high end.
What this estimate assumes
A professionally designed and built conversion of roughly 25–35m² with safe stair access, insulation, electrics, plaster finish and building-control approval.
London and constrained urban sites can exceed these figures. Floor area alone is a poor comparison: structure, roof type, staircase position and bathroom work matter more.
Typical cost breakdown
- Rooflight conversion
- £27,500–£40,000
- Dormer conversion
- £45,000–£60,000
- Hip-to-gable or complex conversion
- £50,000–£75,000+
Usually included
- Structural floor, steels and roof alterations for the selected type
- Staircase, insulation, plastering and standard electrics
- Roof windows or a standard dormer as applicable
- Building-control inspection and normal professional drawings
Usually costs extra
- An en-suite bathroom unless stated
- Party-wall surveyor fees and planning applications
- Premium joinery, fitted furniture or air conditioning
- Major roof replacement or asbestos removal
What affects the price
- Conversion type (Velux cheapest, mansard most expensive)
- Whether an en-suite is included
- Structural work — steels, dormers, staircase position
- Building regs and party wall costs
- Regional labour rates
Red flags to watch for
- No structural engineer drawings referenced
- No building control sign-off included
- No fixed completion date
Questions to ask your provider
- Is building regs sign-off included in the price?
- Are structural calcs and party wall agreements included?
- What is the payment schedule tied to milestones?
- What warranty covers the structural work?
Frequently asked questions
How long does a loft conversion take?
Typically 6–10 weeks depending on complexity.
Do I need planning permission?
Most loft conversions fall under permitted development, but dormers to the front and mansards usually need permission.
Are architect and structural-engineer fees included?
Some design-and-build quotes include them and others do not. Ask for drawings, structural calculations, building control and party-wall work to be listed separately.
Will every loft be suitable for conversion?
No. Head height, roof structure, staircase position and load paths need checking before a price range can become a reliable quote.
Sources and methodology
Reviewed 27 September 2026. Prices vary by specification, access, materials and local labour rates.
- Checkatrade loft conversion cost guide — Published UK ranges by conversion type.
- GOV.UK permitted development technical guidance — Official guidance for household permitted-development limits in England.