A two-room Velux loft conversion costs £34,500 to £40,500 and a rear dormer with two bedrooms and an en-suite costs £48,500 to £56,500 at West Midlands rates, including VAT, drawings, a structural engineer, Building Regulations, a lawful development certificate and a party wall surveyor. Hip to gable and mansard conversions cost more because they rebuild part of the roof. In inner London the dormer is £63,500 to £81,000; in the North East it is £44,500 to £54,500.
- Velux (rooflight): £36,000 to £42,500
- Rear dormer: £48,500 to £56,500
- Hip to gable: £53,000 to £62,500
- Mansard: £59,500 to £70,000
West Midlands rates from Quoteio’s free calculator. For your area, see prices by region.
How much does each type of loft conversion cost?
The type of conversion is the biggest single driver of the price. A Velux conversion keeps the roof as it is and adds rooflights. A dormer builds a box out of the rear roof slope for full head height. A hip to gable straightens a sloping side roof into a vertical gable wall, and a mansard rebuilds the rear slope almost vertically. Each step up means more structure.
| Type | 1 room | 2 rooms | 2 rooms + en-suite |
|---|---|---|---|
| Velux (rooflight) | £27,500 to £32,500 | £34,500 to £40,500 | £36,000 to £42,500 |
| Rear dormer | £36,500 to £43,000 | £47,000 to £55,000 | £48,500 to £56,500 |
| Hip to gable | £40,000 to £47,000 | £52,000 to £60,500 | £53,000 to £62,500 |
| Mansard | £45,000 to £52,500 | £58,000 to £68,000 | £59,500 to £70,000 |
Standard spec, VAT and professional fees included, West Midlands rates.
Notice that the second room costs far less than the first. Most of a loft’s cost is the shell: steels, the new floor, the staircase and, for a dormer, the dormer box itself. Those don’t double when you add a second bedroom. Our loft room cost guide looks at single-room conversions in more detail.
Velux or dormer: which should you choose?
A Velux conversion is the cheapest way into the loft, at £34,500 to £40,500 for two rooms, but it only works if you already have good head height under the ridge, because the roof shape doesn’t change. It suits steep Victorian and Edwardian roofs.
A rear dormer, at £47,000 to £55,000 for two rooms, adds usable floor space with full standing height, which is what makes room for an en-suite and proper wardrobes. It is the most common choice on semi-detached and terraced houses, and is often possible under permitted development.
On a semi-detached or end of terrace house with a hipped roof, a hip to gable conversion (often combined with a rear dormer) adds the most space and room for a staircase in the right place. A mansard gives the biggest room of all but nearly always needs planning permission.
Where does the money go in a dormer loft conversion?
Here is how the engine builds up the standard two-room rear dormer with an en-suite. Figures are ex VAT.
| Item | Cost ex VAT |
|---|---|
| Dormer structure (2 rooms) | £25,000 |
| Studding | £1,360 |
| Dormer roof construction | £3,840 |
| Scaffold | £1,200 |
| Electrics | £4,010 |
| Heating & plumbing | £3,210 |
| En-suite fittings | £1,300 |
| Architectural drawings | £1,200 |
| Structural engineer | £800 |
| Building regulations | £500 |
| Lawful development certificate | £264 |
| Party wall surveyor | £700 |
| VAT at 20% | £8,677 |
| Total | £52,061 |
Shown as a range in the calculator (£48,500 to £56,500). See how we price and set the range.
How much does the spec level add?
Spec covers the quality of finishes, joinery, sanitaryware and the depth of the professional design work. For the same two-room rear dormer with an en-suite:
- Standard: £48,500 to £56,500
- Mid: £54,000 to £63,000
- High: £62,500 to £73,500
Going to three rooms with an en-suite at standard spec brings the dormer to £59,000 to £69,000, which is only possible on larger roofs.
How much does a loft conversion cost in my region?
Lofts follow the same regional pattern as extensions. Steels, scaffold and skilled labour cost more in London and the South East, where site access and party walls also make the work slower.
| Region | Velux, 2 rooms | Dormer, 2 rooms + en-suite |
|---|---|---|
| Inner London | £45,500 to £58,000 | £63,500 to £81,000 |
| Outer London | £41,000 to £52,000 | £57,500 to £72,500 |
| South East | £38,500 to £46,500 | £53,500 to £65,000 |
| East of England | £36,500 to £44,500 | £51,000 to £62,500 |
| South West | £35,500 to £43,500 | £49,500 to £60,500 |
| East Midlands | £33,500 to £41,000 | £47,000 to £57,000 |
| West Midlands | £34,500 to £40,500 | £48,500 to £56,500 |
| North West | £33,500 to £41,000 | £47,000 to £57,000 |
| Yorkshire and the Humber | £32,500 to £40,000 | £45,500 to £55,500 |
| North East | £32,000 to £39,000 | £44,500 to £54,500 |
| Wales | £32,500 to £40,000 | £45,500 to £55,500 |
| Scotland | £34,000 to £41,500 | £47,500 to £57,500 |
| Northern Ireland | £30,500 to £37,000 | £42,500 to £52,000 |
See the full local picture on our London, Yorkshire and West Midlands cost pages, or put your postcode into the calculator.
Does a loft conversion need planning permission?
Many don’t. In England, a loft conversion can usually go ahead under permitted development if it stays within the volume allowance (40m³ for terraced houses and 50m³ for detached and semi-detached houses, including any earlier roof extensions), doesn’t raise the highest part of the roof, and doesn’t put a dormer on the front slope facing the road. Mansards, front dormers, flats and homes in conservation areas usually need full planning. Rules differ in Wales, Scotland and Northern Ireland, so check with your council.
Our estimates include a lawful development certificate (£264 in England), which confirms in writing that the conversion is permitted. It is not compulsory, but buyers’ solicitors often ask for it when you sell.
What do Building Regulations require?
Every loft conversion that creates a habitable room needs Building Regulations approval. The inspector will usually look at:
- Structure: new floor joists and steel beams designed by a structural engineer.
- Fire safety: a protected escape route down through the house, fire doors and mains-wired smoke alarms.
- Stairs: a permanent staircase with enough headroom. Loft ladders don’t count for a bedroom.
- Insulation and ventilation: the roof and dormer walls must meet current thermal standards.
How can you keep the cost of a loft conversion down?
- Choose the simplest type your roof allows. If there is enough head height for a Velux conversion, it costs £13,200 less than a two-room rear dormer at standard spec.
- Stack the bathroom. Putting the en-suite above the existing bathroom keeps the waste pipe run short and avoids boxing in pipes through bedrooms below.
- Decide on the staircase early. Where the stairs land on the floor below drives the whole layout. Changing it after the steels are designed costs time and engineer’s fees.
- Stay within permitted development where you can. It avoids a full planning application and the redesigns that sometimes come with it.
- Get like-for-like quotes. Ask every builder to price the same drawings and say what is included: party wall costs, Building Control fees, fire doors and making good below.
What isn’t included in the price?
- Moving a water tank or a conventional boiler system that sits in the loft.
- Rearranging the floor below to fit the new staircase.
- Fitted wardrobes and eaves storage beyond basic joinery.
- Carpets, decorating and blinds.
- Extra structural work found once the roof is opened up.
Wondering whether converting beats moving? We run the numbers side by side in loft conversion vs moving house.
Common questions
How much does a loft conversion cost in the UK?
At standard spec and West Midlands rates, including VAT and professional fees, a two-room Velux conversion costs £34,500 to £40,500, a rear dormer with two rooms and an en-suite £48,500 to £56,500, a hip to gable £53,000 to £62,500 and a mansard £59,500 to £70,000. London prices are higher and northern prices lower.
Does a loft conversion need planning permission?
Many loft conversions in England are permitted development, so they usually do not need a full planning application, provided they stay within the volume allowance, do not raise the roof ridge and do not put a dormer on the front roof slope facing the road. Mansards, front dormers and homes in conservation areas usually need planning. A lawful development certificate confirms your conversion is permitted. Building Regulations approval is always needed.
Is my loft suitable for a conversion?
The main checks are head height, roof structure and stairs. A common rule of thumb is at least 2.2m from the top of the ceiling joists to the underside of the ridge. Modern trussed roofs need more structural work than traditional cut roofs. You also need space for a staircase that meets Building Regulations. A surveyor or loft specialist can confirm after a visit.
Do I need a party wall agreement for a loft conversion?
In England and Wales, usually yes if you live in a terraced or semi-detached house, because steel beams often sit in the shared wall. You must serve notice on your neighbours before work starts. Our estimates include a party wall surveyor at £700 ex VAT at West Midlands rates; if a neighbour appoints their own surveyor, you normally pay for both.