Loft conversion cost in 2026: what each type really costs
4 min
9
September 2026
Key figures in this guide
One-minute decision
What are you trying to work out?
Use the calculator with your own quantities and rates, then keep a contingency visible from day one.
Open calculatorA loft conversion costs £28,000 - £48,000 in 2026 for a rooflight conversion, £48,000 - £78,000 for a rear dormer, £58,000 - £95,000 for hip-to-gable plus a rear dormer, and £75,000 - £120,000 for a mansard. As a rate, that is roughly £1,800 - £2,700 per square metre of finished floor area.
Loft conversions are the cheapest way to add a bedroom in most UK houses, because the structure and roof already exist. The price swings hugely with the type you choose, so start there rather than with a wish list.
All figures below are 2026 UK prices, including labour and materials but excluding VAT on new-build elements where it does not apply, and excluding furniture.
What a loft conversion costs in 2026
| Type | Typical 2026 cost | Adds | Notes |
|---|---|---|---|
| Rooflight (Velux) conversion | £28,000 - £48,000 | 1 room | Needs existing head height; no roof shape change |
| Rear dormer | £48,000 - £78,000 | 1 bed + shower room | The most common London choice |
| Hip-to-gable plus rear dormer | £58,000 - £95,000 | 1-2 beds + bathroom | Semi-detached and end-of-terrace houses |
| Mansard | £75,000 - £120,000 | 1-2 beds + bathroom | Most space, most structural work, usually needs permission |
| L-shaped dormer | £70,000 - £110,000 | 2 beds + bathroom | Victorian terraces with a rear outrigger |
As a rate, budget £1,800 - £2,700 per square metre of finished floor area in 2026. London and the South East sit at the top of every range, and often 15-25 per cent above it for mansards.
What is included in those figures
- Structural steels, new floor joists and any roof alterations
- Staircase to the new floor, plus fire doors and mains-wired smoke alarms
- Insulation, plasterboard, plastering and decoration
- Electrics, heating and plumbing for the new rooms
- A shower room fitted to a mid-range standard
What is usually extra
| Item | Typical 2026 cost |
|---|---|
| Architect or designer drawings | £1,800 - £5,000 |
| Structural engineer | £750 - £1,600 |
| Planning application (where needed) | £258 householder fee, plus drawings |
| Building regulations, full plans and inspections | £700 - £1,400 |
| Party wall surveyor (per neighbour) | £1,200 - £2,200 |
| Fitted wardrobes and joinery | £2,500 - £9,000 |
| Upgraded bathroom specification | £2,000 - £7,000 |
What moves the price most
- 01Head height. If the ridge gives less than about 2.2 metres you need a dormer or mansard, which doubles the structural work.
- 02Roof type. Trussed roofs need more steel than traditional cut roofs.
- 03Bathroom position. Moving the soil stack or pumping waste upwards adds cost.
- 04Staircase. Losing a bedroom or fighting for landing space often forces a bespoke stair.
- 05Access. Terraced houses with no side access mean everything comes through the house, which adds labour and protection.
How long it takes
- Design, structural drawings and approvals: 8-14 weeks
- Build on site: 7-12 weeks for a dormer, 12-18 weeks for a mansard
- Snagging and sign-off: 1-2 weeks
Is it worth it
A well-built loft bedroom with a shower room typically returns most of its cost in added value in areas where floor space is scarce, and considerably less where land is cheap and extending outwards is easier. Compare it against a rear extension before committing: they cost similar money and add space in very different ways.
How to get a price you can trust
The reason loft quotes vary by tens of thousands is that builders are pricing different jobs. Fix the scope before you ask for numbers.
- 01Decide the type: rooflight, dormer, hip-to-gable or mansard.
- 02Confirm head height and whether permitted development covers it.
- 03Write down the bathroom specification, the number of sockets and the floor finish.
- 04Send every builder the same drawings and the same written brief.
- 05Compare quotes line by line, not by the total.
Renovome does that last part for you: you describe the project once, get a defined scope and programme, and every professional prices the same job.
Related guides
- Do you need planning permission for a loft conversion?
- How to compare builders quotes beyond the headline price
- How long does a house extension or renovation take, start to finish?
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What else to budget, and where to read next
| Item | 2026 cost | Guide |
|---|---|---|
| Structural engineer | £900 - £2,000 | Structural engineer cost in the UK (2026) |
| Architect or designer fees | £2,000 - £10,000 | Architect fees in the UK (2026) |
| Building control | £550 - £1,100 | Building control fees and costs in the UK (2026) |
| Party wall surveyor | £1,200 - £2,500 per neighbour | How to serve a party wall notice, and what it costs |
| Planning application, if needed | £328 | Do you need planning permission for a loft conversion? |
Use the Renovome cost calculator to change the quantities and rates above to your own house, and the planning permission checker to test whether your dormer falls inside permitted development.
Last reviewed: September 2026