UK cost guide · September 2026
How much does a loft conversion cost in 2026?
A mid-range loft conversion of about 30 m² costs, including VAT, in an average UK area outside London:
- Rooflight (Velux): £27,000 to £35,000
- Rear dormer: £47,000 to £58,000 (about £63,500 to £78,500 in London)
- L-shaped dormer: £55,000 to £68,000
- Hip-to-gable: £55,000 to £68,000
- Double hip-to-gable: £63,000 to £78,000
- Mansard: £65,000 to £85,000
We price an L-shaped dormer at the same rates as a hip-to-gable: both cost more than a rear dormer for the extra roof and steel. Allow £3,900 to £8,600 for fees, and more in London.
A loft conversion usually needs three people: an architect or designer to draw it, a structural engineer to work out the steel beams and new floor, and a builder. Get drawings first, then ask at least three builders to quote on the same drawings, so every price covers the same work. Many loft companies offer all three as design and build.
Work out your loft conversion cost
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Already have a loft builder’s price? Check where your quote sits against this range. Still deciding what to do first? Read where to start a home renovation.
Loft conversion prices in 2026
Ranges are for a typical home outside London, including VAT, before fees and contingency. Use the calculator for your size, region and finish.
| Type | Basic | Mid-range | Premium |
|---|---|---|---|
| Rooflight (Velux) (30 m²) | £22,000 to £27,000 | £27,000 to £35,000 | £35,000 to £45,000 |
| Rear dormer (30 m²) | £40,000 to £47,000 | £47,000 to £58,000 | £58,000 to £75,000 |
| L-shaped dormer (30 m²) | £48,000 to £55,000 | £55,000 to £68,000 | £68,000 to £85,000 |
| Hip-to-gable (with rear dormer) (30 m²) | £48,000 to £55,000 | £55,000 to £68,000 | £68,000 to £85,000 |
| Double hip-to-gable (with rear dormer) (30 m²) | £56,000 to £63,000 | £63,000 to £78,000 | £78,000 to £95,000 |
| Mansard (30 m²) | £55,000 to £65,000 | £65,000 to £85,000 | £85,000 to £120,000 |
| Floor area | Basic | Mid-range | Premium |
|---|---|---|---|
| 20 m² | £31,500 to £37,000 | £37,000 to £45,500 | £45,500 to £59,000 |
| 30 m² | £40,000 to £47,000 | £47,000 to £58,000 | £58,000 to £75,000 |
| 40 m² | £47,500 to £56,000 | £56,000 to £69,000 | £69,000 to £89,000 |
Loft conversion costs by region
Labour costs vary across the UK far more than materials. Loft conversion prices in London run about 35% above the UK average outside London, and in Northern Ireland about 18% below it.
| Region | Mid-range cost |
|---|---|
| UK average (outside London) | £47,000 to £58,000 |
| London | £63,500 to £78,500 |
| South East | £54,000 to £66,500 |
| East of England | £50,500 to £62,000 |
| South West | £49,000 to £60,500 |
| West Midlands | £45,500 to £56,500 |
| East Midlands | £44,500 to £55,000 |
| Scotland | £44,500 to £55,000 |
| North West | £43,500 to £54,000 |
| Yorkshire and the Humber | £43,000 to £53,500 |
| Wales | £42,500 to £52,000 |
| North East | £41,500 to £51,000 |
| Northern Ireland | £38,500 to £47,500 |
Which region is my town in? Brighton, Oxford and Southampton are in the South East; Cambridge and Norwich in the East of England; Bristol, Bath and Exeter in the South West; Birmingham and Coventry in the West Midlands; Nottingham and Leicester in the East Midlands; Glasgow and Edinburgh in Scotland; Manchester and Liverpool in the North West; Leeds, Sheffield and Hull in Yorkshire and the Humber; Cardiff and Swansea in Wales; Newcastle and Sunderland in the North East; and Belfast in Northern Ireland. Somewhere else? Type your postcode into the calculator above and it says which region’s prices it uses.
Want it for your area? See local prices and council building control fees for 92 council areas in England and Wales (not every council yet), or loft conversion costs in Scotland, with building warrant fees.
Fees and approvals
Design, engineering and approvals come on top of the building work. Building control: 46 of the 90 councils we checked in England and Wales charge between £750 and £1,000 for a loft conversion, so the table shows that typical range; your council’s own charge is on its local page, and every council is on building control fees by council. We have local pages for 92 council areas; 2 of them don’t show a separate charge for a loft conversion in the schedules we checked, so this figure covers 90.
| Fee | Typical cost | Notes |
|---|---|---|
| Design drawings (planning and building regulations) | £2,400 to £5,400 | Many loft companies offer design and build, so ask whether drawings and calculations are already in the price. |
| Structural engineer | £720 to £2,200 | |
| Building control (council, full plans) | £750 to £1,000 | About half the councils we checked in England and Wales (46 of 90) charge within this range for a loft conversion; current schedules run from £618 to £1,782. |
| Lawful development certificate (England) | £274 | Optional proof that permitted development (work you can do without applying for planning permission) applies. Optional. |
| Party wall surveyor (per neighbour, one surveyor agreed by both sides) | £1,100 to £1,800 | If your neighbour wants their own surveyor, the cost roughly doubles, and the person having the work done normally pays both. Nothing to pay if your neighbour agrees in writing. Optional. |
The calculator adjusts design and engineer fees for your region, so its figures can differ slightly from this table. Council pages use that council’s own building control charge.
Which type of loft conversion is it?
The type of conversion sets the price more than anything else, and quotes do not always say it plainly. These simple drawings show each type, with the words to look for on a quote. Whether your loft can take a particular type depends on its height, roof structure and local rules, so ask your designer or surveyor rather than going by floor area alone. If each builder quoted a different loft type, you are comparing different jobs. Get one set of drawings priced by all three.
Loft conversion with or without an en-suite
Many quotes include an en-suite shower room; many do not. Before you compare prices, check which yours does. Add the en-suite only if the quote leaves it out, and you can tick it in the calculator.
| Type | Conversion only | With an en-suite |
|---|---|---|
| Rooflight (Velux) | £27,000 to £35,000 | £32,000 to £44,000 |
| Rear dormer | £47,000 to £58,000 | £52,000 to £67,000 |
| L-shaped dormer | £55,000 to £68,000 | £60,000 to £77,000 |
| Hip-to-gable (with rear dormer) | £55,000 to £68,000 | £60,000 to £77,000 |
| Double hip-to-gable (with rear dormer) | £63,000 to £78,000 | £68,000 to £87,000 |
| Mansard | £65,000 to £85,000 | £70,000 to £94,000 |
A mid-range en-suite (shower, toilet and basin) adds about £5,000 to £9,000. Add about £600 to £1,200 if the soil pipe (the large waste pipe that takes toilet waste to the drains) is out of reach, so the toilet needs a pump, such as a macerator, which breaks up the waste and pumps it through a narrow pipe. Fees of £3,900 to £8,600 and a 15% contingency come on top of every row, plus a party wall surveyor if your neighbours need one. Many loft companies offer design and build, so ask whether drawings and calculations are already in the price. Each figure is rounded on its own, so a row can differ from its parts by a few hundred pounds.
Often extra on a loft quote
These are easy to leave out of a loft price and can each add real cost. Ask every builder whether they are included:
- Taking out or supporting a chimney breast in the loft or the rooms below
- Moving or replacing the cold water tank in the loft
- Moving a hot water cylinder, or changing the boiler if it can’t heat the new rooms
- Removing any asbestos found in the loft
- Replacing an old fuse board to take the new circuits
A quote may also mark an item, often the steel beams, as “by others”. That means it isn’t in that quote’s price: someone else, usually you, has to supply it or pay for it separately, so the quote is dearer than it looks. The steels are inside our loft prices. If a quote says they are by others, ask the builder what supplying and fitting them would cost, and add that before you compare. As a guide, supplying and fitting the steel beams for a dormer or hip-to-gable loft typically costs about £2,000 to £6,000 (2026 guide price, as you’d pay it). Most published guides don’t say whether their figures include VAT, so read each 2026 guide price on this page as the price you’d pay, with VAT if the firm charges it. The structural engineer’s calculations set how much steel is needed. The quote checker adds this figure for you if you tell it the steels are by others.
If one quote leaves an item out, add it to that quote only when you have a credible price for it, such as a written price from another firm. Otherwise ask the builder to price it, so all the quotes cover the same work.
Stairs, fire safety and the floor below
A loft conversion changes the floor below as well. The new staircase usually takes space from a bedroom, the landing or a cupboard, so ask each builder to mark where it lands and what you lose. The staircase is inside our loft prices. A standard softwood loft staircase, made to measure and fitted with its handrail and balustrade (the posts and rail along the open side of the stairs), typically costs £1,500 to £3,000; oak or bespoke designs £5,000 or more (2026 guide price, as you’d pay it). A PC sum of £1,500 for the staircase is a fair allowance if it covers supplying it only; if fitting is meant to be inside it, it is at the low end, so ask what it covers.
Sound insulation. The new floor needs sound insulation to the rooms below: building regulations ask for it between rooms people live in (Planning Portal). In England and Wales, new internal floors should reach at least 40 dB of airborne sound insulation (Rw) in a laboratory test (requirement E2 and table 0.2 of Approved Document E for England and for Wales). Scotland and Northern Ireland set their own rules, such as Scotland’s standard 5.2, noise reduction between rooms, so ask your builder or building control what applies there. Every one of our loft prices includes sound insulation to the rooms below. If you share a wall with next door, building control may also ask for the party wall to your neighbour’s loft to be improved; that isn’t in our prices, so ask each builder.
These are the building regulations rules in England that shape the stairs and the escape route:
Headroom on the stairs. A new stair to the loft should normally have 2 m of headroom. Where there is not enough space for that, Approved Document K accepts 1.9 m at the centre of the stair and 1.8 m at the side (paragraph 1.13 and diagram 1.4). Where a full stair won’t fit at all, an alternating tread stair (a steep stair with paddle-shaped treads) is allowed, but only to one habitable room, plus a bathroom or toilet as long as it isn’t the only toilet in the house (paragraph 1.29; Approved Document K).
A way out in a fire. An escape window is enough only for floors up to 4.5 m above the ground. If the new loft floor is higher than that, as it usually is on top of a two-storey house, the whole escape route down the stairs must be protected: fire-resisting doors to the rooms off the stairs, and fire-resisting walls around the route, which can mean upgrading existing doors (paragraphs 2.2 and 2.21). An open-plan ground floor is only allowed instead if all of these are done: sprinklers in the open-plan areas; a fire-resisting partition and door between the ground floor and the floors above, placed so that people in the loft can reach a first-floor escape window; and the cooking area enclosed in fire-resisting construction (paragraph 2.23; Approved Document B, volume 1). Mains-wired, linked smoke alarms are needed too, in the stairway at each level, so an alarm on one floor sounds on every floor (Planning Portal).
Work on the ceilings below, making good (repairing plaster and decoration disturbed by the work) and replacing doors are easy to leave off a quote, so check they are priced. A comparison spreadsheet keeps these items visible, and is my loft conversion quote fair? explains what common exclusions mean. Your council's building control charge is on its local page, and if this is your first big project, start with where to start a home renovation.
What's included in these prices
Included
- Structural floor, steels and any strengthening
- Stairs to the new floor
- Insulation, plasterboard and fire protection to building regulations
- Sound insulation in the new floor to the rooms below, which building regulations ask for between rooms people live in (Planning Portal)
- Rooflights or dormer windows
- Electrics, heating and decoration to a finished room
- Mains-wired, linked smoke alarms in the stairway at each level, which building regulations need
- Scaffolding and waste removal
Not included
- An en-suite bathroom (tick it in the calculator)
- Design, engineering and building control fees (shown separately)
- Party wall surveyors
- Fitted wardrobes and eaves storage beyond basic
- Sound insulation beyond what building regulations require, and improving the party wall to a neighbour’s loft if building control asks for it
- Your contingency
What drives the cost
- Type of conversion. Rooflight conversions keep the roof shape and cost least. Dormers add headroom, and an L-shaped dormer adds a second dormer over the back addition; hip-to-gable (one end or both) and mansard conversions rebuild much of the roof and cost the most.
- Headroom. You need enough height in the room and at the top of the new stairs. As a guide, a loft needs a height of at least 2.2 m to convert (Planning Portal), and the new stairs need 2 m of headroom, or 1.9 m at the centre in a loft (stairs and fire safety). Ask your designer to measure yours. If the loft is lower than that, a dormer, raising the roof or lowering the ceilings below adds cost.
- Stairs. Where the new staircase lands decides how much of the floor below is disturbed. The staircase is inside our prices: see stairs, fire safety and the floor below for what it costs.
- Bathroom. An en-suite adds plumbing, drainage and ventilation; tick it in the calculator.
- Fire safety. A loft room above a two-storey house needs a protected escape route, which can mean fire doors throughout, and mains-wired, linked smoke alarms in the stairway at each level.
- Steel. Every dormer needs some steel beams, and they are inside our prices: see what the steels cost. More steel than usual, for a wide dormer, a hip-to-gable or walls below that need extra support, raises the price.
- Where you live. London lofts cost about 35% more than the UK average outside London; mansards are common there and push prices higher still.
Planning, regulations and VAT
Many loft conversions in England are permitted development, meaning they need no planning application, if they stay within volume limits (40 m³ for terraced houses, 50 m³ for others) and do not extend the roof slope at the front facing a road (Class B of the order). Those rights don’t apply in a conservation area, a National Park, an Area of Outstanding Natural Beauty, the Broads or a World Heritage Site (Planning Portal), or where the council has removed them with an Article 4 direction (article 4 of the order).
Dormers. A dormer built this way must also use materials similar in appearance to the house, be set back at least 20 cm from the eaves where practicable (measured along the roof slope; this doesn’t apply to a hip-to-gable, or where the new roof joins the roof of a rear or side extension), and any window in a side wall or side roof slope must be obscure glazed and fixed shut unless the part that opens is more than 1.7 m above the floor of the room (Class B conditions; Planning Portal).
You don’t need a lawful development certificate, on a semi or any other house: it is optional (Planning Portal). For £274 the council confirms in writing that your loft is within the rules, which some people want for certainty or when they sell. Every loft conversion needs building regulations approval.
Party wall. In England and Wales, if you build on or at the boundary, cut into a shared wall (for example to rest a steel beam on it) or dig foundations close to a neighbour’s, you must give notice to every neighbour affected: one, or two if the work touches walls on both sides, which on a terrace usually means both. If a neighbour agrees in writing within 14 days, there is nothing to pay. If they don’t reply, or don’t agree, a party wall surveyor sets out how the work will be done: one surveyor agreed by both sides costs about £1,100 to £1,800 for each neighbour, including VAT. If a neighbour wants their own surveyor, the cost roughly doubles, and the person having the work done normally pays both (GOV.UK explanatory booklet). The Party Wall etc. Act 1996 does not apply in Scotland or Northern Ireland (the Act says where it applies).
Checklist: what to ask loft builders to confirm
Print this or save it as a PDF, one copy for each quote. Mark each line included, separate or not confirmed as quotes come in. An empty amount means unknown, not free.
| Item | What to confirm | Included? Amount? |
|---|---|---|
| Survey and design | Measured survey, headroom check, drawings and structural calculations. Ask whether drawings are already in a design and build price. | |
| Permissions | Permitted development or planning, building control and party wall notices. | |
| Structure | New floor joists (the beams that carry the new floor), steel beams, any work to the wall plates (the timbers along the top of the walls that the roof sits on) and dormer framing. | |
| Stairs and fire safety | Staircase position and headroom, what any PC sum for the staircase covers (supply only, or fitted too), protected escape route and fire doors. | |
| Windows | Rooflights, dormer windows and any escape window. | |
| Services and finishes | Heating, electrics, insulation, plastering and decoration, and making good the rooms below. | |
| Bathroom | En-suite plumbing and drainage, if wanted. | |
| Often extra | Chimney breast, water tank, hot water cylinder, boiler, asbestos and an old fuse board. |
Questions people ask
What is the cheapest type of loft conversion?
A rooflight (Velux) conversion, at about £27,000 to £35,000 including VAT for a mid-range finish, because the roof shape does not change.
How much does a dormer loft conversion cost?
About £47,000 to £58,000 including VAT for a mid-range rear dormer of about 30 m², before fees. Basic and premium finishes run from £40,000 to £75,000.
Does a loft conversion need planning permission?
Often not in England, if it falls within permitted development limits and the house is not in a conservation area or other protected area. Building regulations approval is always needed.
How much does a loft conversion cost in London?
About £63,500 to £78,500 for a mid-range rear dormer including VAT, before fees.
How much does a loft staircase cost?
The staircase is inside our loft prices. As a guide, a standard softwood loft staircase, made to measure and fitted, costs £1,500 to £3,000, and oak or bespoke designs £5,000 or more (2026 guide price, as you’d pay it). Stairs, fire safety and the floor below says what a PC sum for the staircase should cover.
How much does a loft conversion with an en-suite cost?
About £52,000 to £67,000 for a mid-range rear dormer of about 30 m² with an en-suite, including VAT, in an average UK area outside London (September 2026 prices), before fees and contingency. Do not add the en-suite if your quote already includes one.
How do I know which type of loft conversion my quote is for?
Look for the words on the quote and drawings: rooflight or Velux means the roof shape stays the same; dormer means a box-shaped addition on the rear slope; L-shaped dormer means a second dormer on the roof of the back addition, joined to the first; hip-to-gable means the sloping end is rebuilt as an upright wall (double hip-to-gable: both ends); mansard means the rear slope is rebuilt almost vertical. If it is not clear, ask the builder to state it.
How much does an L-shaped dormer cost?
About £55,000 to £68,000 for a mid-range L-shaped dormer of about 30 m², including VAT, in an average UK area outside London, before fees. That is more than a rear dormer of the same size (£47,000 to £58,000), because of the second dormer roof over the back addition and the extra steel. We price an L-shaped dormer at the same rates as a hip-to-gable: both cost more than a rear dormer for the extra roof and steel.
How much do the steels for a loft conversion cost?
They are inside our loft prices. As a guide, they cost about £2,000 to £6,000 to supply and fit (2026 guide price, as you’d pay it). If a quote says the steels are by others, add a price for them before you compare: steels on a loft quote explains how.
Sources and method
Our ranges combine published 2026 UK cost guides, industry data and our own survey of council fees. We check them every quarter. They are budget ranges, not quotes: always get at least three detailed written quotes. Read how Estiquote estimates work, or download the full cost data.
- Checkatrade: Loft conversion cost (March 2026)
- Homebuilding & Renovating: Loft conversion costs (July 2026)
- Federation of Master Builders: Loft conversion cost breakdown (September 2025)
- MyJobQuote: Loft conversion cost (September 2026)
- ASA and CAP: Compulsory costs and charges, VAT (CAP Code rule 3.18)
- MyJobQuote: Rear dormer loft conversion cost (October 2026)
- Build It: How much does a loft conversion cost? (August 2026)
- MyJobQuote: Hip to gable loft conversion cost (October 2026)
- Estiquote: Building control fees by council (September 2026)
- Planning Portal: Application fees in England from 1 April 2026
- Checkatrade: Party wall surveyor cost (June 2026)