Cost guides › Loft conversion
United Kingdom
How much does a loft conversion cost?
A rear dormer loft conversion creating 30 m² of new floor space with an en-suite shower room typically costs £52,000 including VAT, with most quotes between £40,500 and £67,600. A simpler finish without the en-suite is about £44,000, and a high-spec version with better insulation, hardwood floors, built-in eaves storage and upgraded roof windows is around £57,400. Choose a rooflight-only (Velux) conversion, hip-to-gable or mansard in the calculator to price them on their own.
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mid-range, typicalCost by region
| Location | Basic | Mid-range | Premium |
|---|---|---|---|
| London | £47,000 | £55,400 | £61,100 |
| Scotland | £44,600 | £52,600 | £58,100 |
| South East | £44,000 | £51,900 | £57,400 |
| East | £43,500 | £51,400 | £56,800 |
| North West | £43,400 | £51,300 | £56,700 |
| South West | £43,100 | £50,900 | £56,300 |
| West Midlands | £43,100 | £50,900 | £56,300 |
| Wales | £42,900 | £50,700 | £56,000 |
| East Midlands | £42,800 | £50,600 | £55,900 |
| North East | £42,800 | £50,500 | £55,900 |
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| Yorkshire and The Humber | £42,600 | £50,300 | £55,600 |
What's included
Mid-range
- Drawings, structural engineer's calculations and building control fees
- Scaffolding with a temporary roof while the dormer is built
- Full-width rear dormer: steel beams, timber frame, flat roof, cladding and windows
- New floor joists, boarding and sound insulation between the loft and the floor below
- Insulation between and under the rafters, vapour control layer, plasterboard and skim
- New staircase with the landing below altered
- Fire doors onto the stair and mains-wired linked smoke alarms for the escape route
- Electrics, lighting and radiators connected to the existing heating
- En-suite shower room with shower, WC and basin
- Doors, skirting, flooring and decoration
What affects the cost
Type of conversion
A rooflight conversion keeps the roof shape and only adds windows, so it is the cheapest, but it needs enough head height already. A rear dormer adds a box to the back slope and is the usual choice on terraces and semis; hip-to-gable rebuilds a sloping side as a gable wall, and a mansard rebuilds the whole rear slope almost vertical, which is the most work.
Head height and structure
You need roughly 2.2 m from the top of the ceiling joists to the underside of the ridge for a comfortable room. Older houses with purlins and struts usually need steel beams to open the space, and modern trussed roofs need more steel than traditional cut roofs.
Staircase and fire safety
The new stair has to fit over the existing one without losing too much of the landing below. Building regulations also require a protected escape route, which normally means fire doors onto the stairs and linked smoke alarms on every floor.
En-suite and plumbing
An en-suite adds a lot of value but needs a route for the waste pipe to the soil stack and good water pressure at the top of the house. A combi boiler or a new cylinder may be needed if the existing hot water can't cope.
Party walls and neighbours
Steels bearing into a shared wall on a semi or terrace come under the Party Wall Act. If a neighbour does not consent, each side's surveyor fees are paid by you, which is why a mid-terrace costs more than a detached house.
Access and location
Scaffolding over a conservatory, a narrow alley or a front garden adds cost, and London prices run well above the national figure. Materials may need to come through the house on terraces without rear access.
How to save
- Get a party wall award agreed early and ask neighbours whether they will accept one agreed surveyor instead of two.
- Keep the bathroom above an existing bathroom so the waste pipe run to the soil stack is short.
- Stay within permitted development limits so you avoid a planning application and redesign.
- Compare quotes line by line: steels, stair, windows, en-suite and making good below are the items that differ most.
Grants, tax and rules
Planning permission
In England most loft conversions are permitted development if the extra roof volume stays within 40 cubic metres on a terraced house or 50 cubic metres on other houses, nothing goes higher than the existing roof or forward of the front roof slope facing a road, there are no balconies, and side windows are obscure-glazed and fixed below 1.7 m. Conservation areas and other designated land need a planning application.
Party Wall Act
If your work affects a shared wall, you must give your neighbour notice between 2 months and a year before you start. Build that into your timetable before booking the builder.
Building regulations and VAT
Every loft conversion needs building regulations approval for structure, fire safety, insulation and the stair, whatever the planning position. Electrical work must be done by a registered electrician (Part P) or notified to building control. Our figures include 20% VAT.
Frequently asked questions
How much does a loft conversion cost in the UK?
A rear dormer creating 30 m² with an en-suite costs around £52,000 including VAT, with most quotes between £40,500 and £67,600. Without the en-suite and with a simpler finish it is about £44,000.
Is a Velux loft conversion cheaper than a dormer?
Yes, clearly, because the roof structure stays as it is and there is no dormer to build or large scaffold with a temporary roof. It only works if the loft already has enough head height in the middle, and you lose usable floor near the eaves.
Do I need planning permission for a loft conversion?
Usually not in England, if you stay within the permitted development limits: 40 cubic metres of extra volume on a terraced house, 50 on others, nothing above the ridge and no dormers on the front slope facing a road. Mansards, front dormers and anything in a conservation area normally need planning permission.
How long does a loft conversion take?
A rear dormer normally takes eight to twelve weeks on site, most of it with you living in the house. The disruption downstairs is mainly at the start, when the scaffold goes up, and near the end, when the stair is cut in.
Does a loft conversion add value?
Adding a bedroom with an en-suite is one of the most reliable ways to add space and value, especially where moving house costs a lot. How much depends on your street and whether the finished room feels like a proper bedroom with full head height.
What is not included in the price?
Moving a water tank, boiler or chimney breast, a planning application where one is needed, strengthening foundations, asbestos removal and furniture are extra. Ask for these to be priced separately so quotes compare fairly.
How this estimate is calculated
Work hours: 660.7 · Labour: £24,603 · Materials: £18,704
Sources: ONS Annual Survey of Hours and Earnings, tables 14 and 15; Regione Toscana, Prezzario dei Lavori 2026 (CC BY 4.0); ECB exchange rates; market check: Rear dormer ~30 m2 with en-suite, incl. VAT. Checkatrade loft conversion cost guide (updated Mar/Aug 2026: Velux £27.5k, dormer £50k, hip-to-gable £60k, mansard £65k; dormer £1,670/m2); bestbuilders.co.uk per-m2 guide 2026 (rear dormer £1,650-2,300/m2, 30 m2 £50-69k); homebuilding.co.uk loft conversion costs (QS Tim Phillips, 2026, ex VAT: rooflight £30-45k, dormer £45-75k).
Last reviewed 26 September 2026 · How we calculate costs · Editorial policy