How much does a loft conversion cost in the UK?
A loft conversion costs £45,000 on average in the UK. Most jobs fall between £22,000 and £75,000 for the project. Type of conversion: Rooflight £22,000 to £32,000; Dormer £40,000 to £58,000; Mansard £55,000 to £75,000. Prices reviewed June 2026.
A loft conversion, sometimes called an attic conversion, is one of the best-value ways to add a bedroom and often a bathroom without losing garden space. What you pay depends mostly on the roof type you choose.
Loft conversion cost calculator
Use the calculator to price your loft conversion in 2026. Adjust the options and area for a UK cost range. Nothing is sent anywhere.
To price the whole job, use the extension cost calculator, loft conversion cost calculator or garage conversion cost calculator.
Loft conversion cost breakdown
Typical loft conversion costs, by option:
| Type of conversion | Typical UK cost |
|---|---|
| Rooflight / Velux | £22,000 to £32,000 |
| Dormer (most common) | £40,000 to £58,000 |
| Mansard / hip-to-gable | £55,000 to £75,000 |
| + Add an en-suite bathroom | add £3,500 to £7,000 |
What's included in the price?
Typical loft conversion prices include:
- Structural work, new floor joists and staircase
- Insulation, plastering, electrics and heating
- Windows or dormer construction
- Building control sign-off
What changes the price?
The things that move loft conversion prices most:
Roof type: a rooflight (Velux) conversion is cheapest, a dormer is the common choice, a mansard is the most expensive
Whether you add an en-suite bathroom
Head height and whether the roof needs raising
Finish level and staircase position
How the price is built up
The price is built up from the structural work first: new floor joists to carry a habitable load, steel beams where needed, roof alterations and insulation to meet building regulations. On top of that sits the fit-out, the new staircase, plastering, electrics, heating, flooring and decoration, plus any en-suite. Professional fees for drawings, a structural engineer and the building control sign-off, along with a party wall agreement where you share a wall, add a few thousand pounds before any building starts. Labour is the bigger share on most loft jobs, usually around 55 to 65 percent of the total, with materials, fittings and the new staircase making up the rest.
Ways to keep the cost down
- A rooflight or Velux conversion keeps the existing roofline and avoids major structural change, so it sits at the bottom of the band, near £22,000, where the head height already works.
- Putting the new bathroom back to back with existing plumbing, or directly above a soil stack, cuts the pipework run and trims the en-suite cost.
- Get written consent from neighbours for the party wall rather than appointing a surveyor, which can save £1,000 to £2,000 per neighbour.
- Keep the structure and layout simple and handle decoration or flooring yourself once the trades are out, rather than paying for changes mid-build.
Does where you live change the cost?
In London, a loft conversion typically costs around £58,500 for the project, about 30% above the UK average of £45,000. In the North, Scotland and Wales the guide figure is nearer £41,500.
| Region | From | Typical | Up to |
|---|---|---|---|
| Midlands / East (UK average) | £22,000 | £45,000 | £75,000 |
| London | £28,500 | £58,500 | £97,500 |
| South East / South West | £25,500 | £51,500 | £86,500 |
| North / Scotland / Wales | £20,000 | £41,500 | £69,000 |
Guide prices for the project, scaled with the same regional multipliers as the calculator. Not quotes.
Loft conversion cost in major UK cities
| City | From | Typical | Up to |
|---|---|---|---|
| Belfast | £18,500 | £38,500 | £64,000 |
| Birmingham | £21,500 | £44,000 | £73,500 |
| Bristol | £24,000 | £49,500 | £82,500 |
| Cardiff | £20,500 | £42,500 | £70,500 |
| Edinburgh | £21,500 | £44,000 | £73,500 |
| Glasgow | £20,000 | £40,500 | £67,500 |
| Leeds | £20,500 | £42,000 | £70,000 |
| Liverpool | £20,000 | £41,500 | £69,000 |
| London | £28,500 | £58,500 | £97,500 |
| Manchester | £21,000 | £43,000 | £72,000 |
| Newcastle | £20,000 | £40,500 | £67,500 |
| Sheffield | £20,000 | £41,500 | £69,000 |
City guide estimates, scaled by local labour costs. Indicative averages for loft conversion, not quotes.
Prices in London and the South East run 15 to 30 percent above the national figures, mainly on labour.
Common questions
Do I need planning permission for a loft conversion?
Many loft conversions fall under permitted development, but dormers facing a road, mansards, and homes in conservation areas usually need planning permission. Building control sign-off is always required.
Does a loft conversion add value?
A well-built loft conversion that adds a double bedroom and en-suite typically adds more to the property value than it costs, especially in higher-value areas, though that is never guaranteed.
Which loft conversion is cheapest?
A rooflight or Velux conversion is cheapest because it keeps the existing roof line. A dormer costs more but adds head height and floor space, which is why it is the most common choice.
How long does a loft conversion take?
A loft conversion usually takes 6 to 10 weeks on site for a straightforward rooflight or dormer, and 10 to 14 weeks for a larger dormer or mansard with an en-suite. Allow several more weeks beforehand for drawings, a structural engineer, building control and any party wall agreement. On a typical £45,000 project, the bulk of the time goes on the structural opening-up, the new staircase and the fit-out, so weather and access rarely change the overall length by much.
Do I need a structural engineer for a loft conversion?
Yes, almost every loft conversion needs a structural engineer. The existing ceiling joists are not built to carry a habitable floor, so new joists and usually steel beams are designed to take the load and tie into the walls. The engineer's calculations are needed for building control approval. Their fee is generally £500 to £1,500 and forms part of the professional fees, which run roughly £3,000 to £8,000 on a typical project once drawings and the building control charge are included.
Does raising the roof for head height cost more?
Yes, raising the roof adds noticeably to the cost. Building regulations want sensible head height over the stairs and floor area, and where the existing roof is too low the options are to lower the ceiling below or partly rebuild the roof, both of which add labour and materials. Roof-raising work can add several thousand pounds and may also need full planning permission rather than permitted development, so on a low roof the project can move from the typical £45,000 towards the upper £75,000 end of the band.
Can you do a loft conversion for £10,000?
A full loft conversion for £10,000 is not realistic in 2026. Even the cheapest type, a rooflight (Velux) conversion, usually starts from about £22,000 once you include a fixed staircase, insulation to current building regulations, flooring, windows and wiring. A £10,000 budget tends to cover only a boarded storage loft with a hatch, not a habitable room that meets building regulations.
Is it worth converting a loft?
Converting a loft is usually worth it where you need an extra bedroom and would otherwise move. A conversion typically costs around £45,000, and can range from about £22,000 for a rooflight job to £75,000 for a mansard with an en-suite. It uses space you already own and avoids the cost and disruption of moving. Whether the added value covers the spend depends on your area, the finish and the roof type, so it is worth checking local sale prices first.
What is the 4 year rule for loft conversions?
The old 4 year rule made unauthorised building work immune from planning enforcement after four years. For breaches on or after 25 April 2024 in England that period is now ten years, so a loft conversion built without the permission it needed can be enforced against for a decade. It is not a route to plan around: doing it properly with permitted development checks or planning permission, plus building control, costs far less than unpicking non-compliant work.
Can I do a loft conversion myself?
Some of it, but not the structural parts. New floor joists, steels and the staircase opening need a structural engineer's calculations and building control sign-off, so this is not a job to do unaided. A capable DIYer can handle insulation, boarding and decorating to save on the labour that runs at roughly 55 to 65 percent of the total. The steelwork, staircase and roof changes should be left to a builder.
Official guidance and sources
The rules and schemes referenced on this page come from these official UK sources. The price figures are Costwise's own; see how we price.
- Planning permission: common projects Planning Portal · Many loft conversions are permitted development within limits; larger dormers may need permission.
- When you need planning permission GOV.UK · When planning permission is needed; building regulations apply to the conversion either way.
These are independent guide prices based on typical UK jobs in 2026. Your actual cost depends on your property, spec, access and where you live. Always get at least three written quotes before committing.