Cost calculator
Loft conversion cost calculator
Loft conversions are priced by structural complexity, not by the floor area you gain. Head height, roof structure and where the staircase can legally land will decide the price long before the finish does.
Usable floor area with at least 1.9m head height.
Broad trade availability keeps day rates near the national average.
Estimated range, ex VAT
£38,000 – £71,000
- Labour (typical)
- £31,500
- Materials (typical)
- £23,000
Guidance only. A real quotation depends on site conditions, specification and access — which is exactly what an independent review of your own quote will tell you.
What affects the cost
Conversion type
Rooflight conversions are cheapest; dormers add roof structure and cladding; hip-to-gable and mansard involve rebuilding roof geometry.
Existing roof structure
Trussed roofs (most post-1965 homes) need a new structural floor and steels before anything else happens.
Staircase position
Fitting a compliant staircase often means reconfiguring a bedroom below — that cost sits outside the loft.
Fire safety compliance
Protected escape route, fire doors to habitable rooms, mains-linked alarms and sometimes a sprinkler system.
Ensuite and services
Pumped waste, extended heating circuits and a boiler that can serve another bathroom.
Regional pricing differences
Materials cost roughly the same everywhere in the UK; labour does not. Use the region selector above to apply a local index — London and the South East typically run 15–30% above the national average, while the North East, Northern Ireland and Yorkshire sit below it.
Labour vs materials
Roughly 58% of this type of work is labour and 42% materials. Structural carpentry, steelwork and roofing labour dominate. Fixed costs — staircase, fire doors, building control — apply even to the smallest conversion.
Common hidden costs
- Upgrading doors and the stairwell throughout the house to satisfy the escape route requirement.
- Party wall awards for terraced and semi-detached homes — typically £1,000–£2,500 per neighbour.
- Insulation upgrades where existing rafters are too shallow, forcing a sarking or over-rafter solution.
- Redecoration of the floor below after steels are dropped in.
How to save money
- Choose rooflights over a dormer wherever head height allows; the saving is often £12,000+.
- Place the ensuite directly above an existing bathroom so waste and supply runs stay short.
- Keep the ridge line unchanged — planning and structure both get cheaper.
- Ask whether the quote includes the staircase, fire doors and building control certificate. Many do not.
Frequently asked questions
How much is a loft conversion in the UK?
Rooflight conversions typically £30,000–£45,000; dormers £45,000–£70,000; hip-to-gable and mansard £60,000–£100,000+ ex VAT.
Do I need planning permission for a loft conversion?
Many fall under permitted development, but mansards, front dormers and flats do not. Building regulations approval is always required.
What head height do I need?
You want at least 2.2m from floor joist to ridge before conversion; 1.9m minimum over the staircase after the new floor is built.
How long does a loft conversion take?
8–12 weeks for a typical dormer, longer for mansards or where scaffolding access is difficult.
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