DATA-BACKED GUIDE · UPDATED JULY 2026
Loft conversion cost UK: room-in-roof, dormer and hip-to-gable prices
A loft conversion is one of the most reliable ways to add a bedroom or office without losing garden space. The catch is that no two lofts are the same, so quotes for what looks like a similar job can land far apart. The real prices on this page come from actual homeowners rather than a showroom estimate, so you can see what people across the UK have genuinely paid for room-in-roof, dormer and hip-to-gable work.
The quick version
- The three common types, room-in-roof, dormer and hip-to-gable, sit at different price points, with a simple room-in-roof usually the cheapest place to start.
- Head height and roof structure decide a lot before a single quote is written. Trussed roofs need more steelwork than older cut roofs, which pushes the cost up.
- Most loft conversions fall under permitted development if they stay within the size limits, so full planning permission is often not needed, but building regulations sign-off still is.
- Building regulations sign-off is a separate step from planning and covers the stairs, fire safety and insulation, not just the extra floor space.
- An ensuite adds real cost through plumbing runs and waterproofing, so a plain bedroom conversion and one with a bathroom are not comparable jobs.
- Access affects labour time as much as design does. A terraced house with no side access means materials and spoil are carried through the home, which shows up in the final bill.
What people actually paid
Real prices, in people's own words
- £15,000“£15k”
- £15,000“£15k”
- £38,000“Room only (no dormer) everything but carpets for 38k”
- £38,000“38k”
- £50,000“50k for a hip to gable plus dormer”
- £50,000“50k inc vat”
Genuine amounts posted publicly. We publish the price and the quote, never the person.
Why the price varies so much
Two lofts that look identical from the street can produce very different quotes, and most of the gap comes down to things you cannot see from outside. The roof structure matters first: a trussed roof needs more steel to open up than an older cut roof, and that steel is priced by the ton delivered and craned in, not guessed. Available head height decides whether you can get away with rooflights or need a full dormer built out, which is a much bigger job in materials and labour. Where the new staircase has to land changes how much of the existing first floor gets disturbed, and a conversion with an ensuite costs more than a plain bedroom because of the plumbing runs and waterproofing involved. Access plays a real part too: a terraced house with no side access means everything, from scaffolding to spoil, is carried through the home rather than round it, and that adds time. On top of all this sits who you are actually paying. A small local builder pricing the job themselves tends to quote differently from a larger regional firm with a sales team and project managers layered on top, and firms owned by bigger construction groups often carry overheads that a sole trader does not. Region matters as well, since labour rates and the cost of skilled tradespeople for steel and roofing work are not the same in every part of the country. Add the type of dormer or the choice of rooflights on top of all that, and the wide spread of prices on one street starts to make sense.
How to pay less
- Get at least three quotes from firms that have done your style of roof before, and check each one includes structural steel and building control fees rather than leaving them as a separate line to be added later.
- Rooflight or Velux conversions are cheaper than a full dormer, so if you already have the head height, you may not need to rebuild the roofline at all.
- Keep the bathroom close to existing soil pipes to cut plumbing costs, rather than putting it at the far end of the loft where new runs have to be built in.
- Book the work outside the busy spring and summer window when builders are stretched and prices firm up, and you have less room to negotiate.
- Ask each firm to itemise the quote by stairs, structure, insulation, electrics and finishing, so you can see exactly where one quote is cheaper than another instead of comparing two lump sums.
- If your loft already has good head height, say so upfront. A conversion that avoids raising the roof line removes a large chunk of cost before anyone starts pricing steel.
Common questions
Do I need planning permission for a loft conversion?
Often no. Most loft conversions fall under permitted development as long as they stay within the volume limits and do not extend beyond the roof slope at the front. You will still need building regulations sign-off, which covers the stairs, fire escape and insulation and is a separate process from planning.
How long does a loft conversion take?
A straightforward room-in-roof or rooflight conversion is usually the quickest, while a dormer or hip-to-gable takes longer because more of the roof is opened up and rebuilt. Weather and steel delivery can stretch the timeline, so ask your builder for a realistic schedule in writing before you sign anything.
Will VAT be added to the quote?
Most building work carries 20% VAT, so check whether a quote includes it or not before you compare figures. A price that looks lower may simply have left the VAT off, which changes the comparison completely once it is added back in.
Is a dormer always more expensive than a room-in-roof conversion?
Usually, yes. A dormer means rebuilding part of the roof structure to add headroom and floor space, which brings extra steel, roofing and weatherproofing costs that a simple room-in-roof job avoids. If your loft already has enough head height for a room-in-roof or rooflight conversion, that route is normally the cheaper of the two.
What pushes a loft conversion quote up unexpectedly?
The most common surprises are the roof structure needing more steel than first thought, poor access forcing everything to be carried through the house, and an ensuite bathroom being added partway through design. Ask your builder to flag any of these risks before work starts, rather than finding out once the roof is already open.
Should I compare quotes on the total price alone?
No. Two quotes with the same total can cover very different work, so ask each firm to break the price down by structure, stairs, insulation, electrics and finishing. Also check whether VAT, building control fees and structural steel are included, since leaving any of these out is the easiest way for a quote to look cheaper than it actually is.