How much does a loft conversion cost in the UK?
Updated 16 October 2026 · Reviewed by Steve Wolfe
A loft conversion in the UK typically costs £28,000 to £50,000 for a rooflight (Velux) conversion and £45,000 to £80,000 for a rear dormer, including VAT. Hip-to-gable and mansard conversions cost more. The size, an en-suite, steelwork and where you live move the price most.
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Typical costs
Typical UK prices including VAT, for a three-bed semi or terrace with about 25 to 30 m² of new floor space.
| Type | Typical cost |
|---|---|
| Rooflight (Velux) £28,000–£50,000 Roof windows set into the existing roof slope. Needs good head height already. On site: 4 to 6 weeks | £28,000–£50,000 |
| Rear dormer £45,000–£80,000 A box-shaped extension on the back roof slope, giving full head height. The most common type. On site: 10 to 12 weeks | £45,000–£80,000 |
| Hip-to-gable £55,000–£90,000 The sloping side of the roof is built up into a vertical wall. Often combined with a rear dormer on semis. | £55,000–£90,000 |
| Mansard £65,000–£120,000 The back roof slope is rebuilt almost vertical. Usually needs planning permission. | £65,000–£120,000 |
Our reading of the published guides listed under Sources, rounded and including VAT. Most guides don't say clearly whether VAT is included, which explains some of the gap between them. Add professional fees and a contingency.
What changes the price
- Type and size. A dormer costs more than roof windows because it builds out the roof to give full head height. Every extra square metre adds cost, so a wider dormer or a hip-to-gable adds a lot.
- An en-suite. In our example below, adding a small shower room moves the price up by about £13,000 to £18,000. It costs more if the waste pipe is hard to route.
- Steelwork and structure. Most conversions need steel beams to carry the new floor and roof. Weak ceiling joists, a low ridge or an awkward roof shape add more.
- Stairs. A staircase that fits neatly over the existing one is cheapest. Losing part of a bedroom to make room for it is common.
- Finish. Fitted storage, bigger or better windows, underfloor heating and higher-end bathroom fittings all push towards the top of the range.
- Fees. Drawings, structural calculations, building control and any party wall surveyor are often quoted separately. Ask whether they're included.
Where the money goes
Which? estimates that labour is about 35 to 40% of the cost of a loft conversion, materials 25 to 30%, and fittings like windows, sanitaryware and lighting 10 to 15%, with a contingency of 10% or more on top. Checkatrade's breakdown of a £50,000 dormer includes about £4,750 for scaffolding, £6,000 for steel, £8,250 for roof coverings and £2,750 for the staircase.
London and the regions
Materials cost much the same across the country. What changes is labour, access and parking. Building cost data from BCIS puts inner London about 21% above the UK average and outer London about 14% above, with the South East about 7% above and the North East and Yorkshire about 11% below. That's a smaller gap than the "30 to 50% more in London" some guides suggest.
Before you get quotes
- Check whether your house has had its permitted development rights removed, or is in a conservation area.
- Ask each firm what's included: drawings, structural calculations, building control fees, scaffolding, the stairs, decorating and the bathroom fittings.
- Keep a contingency of at least 10% for surprises in the roof.
- Get two or three quotes for the same specification, so you're comparing like with like.
An example Ballpark
What Ballpark gave for this job on 16 October 2026. It’s an example we worked out, not a customer’s price.
Rear dormer loft conversion on a 1930s three-bed semi in Birmingham. New bedroom with a small en-suite shower room, stairs up from the landing. Mid-range finish.
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Basic dormer, bedroom only £45,000–£62,000
Rear dormer, new stairs, insulation, electrics and finished bedroom without the en-suite.
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Dormer with en-suiteClosest to the job £58,000–£80,000
Rear dormer, stairs from the landing, bedroom and small en-suite shower room, mid-range finish.
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Higher-spec dormer suite £78,000–£100,000
Larger dormer with en-suite, fitted storage, upgraded windows, bathroom and flooring, plus extra heating work.
Based on
- Building regulations and structural engineer fees included
- No party wall or planning fees included
- Existing roof is standard cut timber, no major structural surprises
- Mid-range finish, Birmingham prices
What a trade will ask you
Have answers ready and your quotes (and your ballpark) will be closer to the real price.
- What shape is your roof, and is the house terraced, semi-detached or detached?
- Roughly how much head height is there in the loft now?
- Dormer, or roof windows only?
- Do you want an en-suite?
- Where would the stairs go?
- Is the house in a conservation area?
Common questions
Do I need planning permission for a loft conversion?
In England, often not. Most rear dormer and rooflight conversions are permitted development if the new roof space adds no more than 40 m³ on a terraced house or 50 m³ on other houses, nothing goes above the highest part of the existing roof, and there's no dormer on a roof slope facing the road. Conservation areas, National Parks and flats don't get these rights. Wales and Scotland have their own rules, so check with your council.
Do I need building regulations approval?
Yes. Every loft conversion needs building regulations sign-off for the structure, fire safety and escape, the stairs and insulation, even when it doesn't need planning permission.
Do I need a party wall agreement?
If you're in a semi or terrace and the work cuts into the shared wall, for example to take steel beams or remove a chimney breast, you must give your neighbours notice between two months and a year before work starts (England and Wales).
How long does a loft conversion take?
About 4 to 6 weeks on site for a rooflight conversion and 10 to 12 weeks for a dormer, once the drawings, structural calculations and any approvals are done.
Why does a loft conversion cost more in London?
Mostly labour, access and parking rather than materials. Building costs in inner London run about a fifth above the UK average and outer London about 14% above, while the North East and Yorkshire run about 11% below.
Are your prices including VAT?
Yes. Every price on this page includes VAT. Many guides quote prices before VAT, so check which you're comparing.
What would yours cost?
Describe your loft conversion and get a ballpark for your house in a couple of minutes. Free, and you don’t have to get quotes.
Get my ballparkSources
- Checkatrade, loft conversion cost guide (Mar 2026). Prices for a 30 m² loft by type, cost breakdown and timings
- HomeBuilding & Renovating, loft conversion costs (Jul 2026). Prices by type and per m², with a quantity surveyor
- Federation of Master Builders, loft conversion cost breakdown (Sep 2025). Starting prices by type from a member firm
- Beams Renovation, loft conversion costs (Jun 2026). Dormer prices including VAT, UK and London
- Which?, loft conversion costs (Apr 2026). How the cost splits between labour, materials and fittings
- BCIS location factors (December 2025), published in the Department for Education's school capital allocations 2026 to 2027 (Dec 2025). Regional building cost differences
- GOV.UK, permitted development rights for householders, technical guidance (Class B) (Sep 2019). Volume limits and conditions for loft conversions in England
- GOV.UK, party walls and building work. Notice periods for work on a shared wall