Last reviewed: September 2026. The figures below are typical ranges from published UK cost guides, not quotes.
If you're thinking about converting your loft, one of the first questions is how much it will cost. The honest answer is that it varies a lot with the type of conversion, the size and structure of your loft, the finish you choose and where you live. Here are the typical ranges published by two widely used UK cost guides in 2026, so you can set a realistic budget before you speak to anyone.
Typical Loft Conversion Costs by Type
| Conversion type | Checkatrade (March 2026, 30m² loft) | HomeBuilding & Renovating (July 2026) |
|---|---|---|
| Velux / rooflight | £22,500 – £30,000 | £30,000 – £45,000 |
| Dormer | £40,000 – £60,000 | £45,000 – £75,000 |
| Hip-to-gable | £50,000 – £70,000 | £55,000 – £85,000 |
| Mansard | £50,000 – £80,000 | £70,000 – £120,000+ |
Put together, that gives typical ranges of roughly £22,500–£45,000 for a rooflight conversion, £40,000–£75,000 for a dormer, £50,000–£85,000 for a hip-to-gable and £50,000–£120,000 for a mansard. These are the ranges we use across this site.
Velux (Rooflight) Conversion
A rooflight conversion keeps the existing roof shape and adds roof windows. It is usually the cheapest type because there is less structural work, but it only suits lofts that already have enough head height. Read more in our Velux vs dormer comparison.
Dormer Conversion
A dormer builds out from the roof slope to add headroom and floor space. It is the most common type in the UK and suits many semi-detached and terraced houses.
Hip-to-Gable Conversion
A hip-to-gable conversion straightens the sloping end of a hipped roof into a vertical gable wall, often alongside a rear dormer. The extra structural work puts it above a dormer on price.
Mansard Conversion
A mansard rebuilds one or both roof slopes almost vertically. It creates the most space, costs the most and normally needs planning permission.
Extra Costs to Budget For
The headline price is not always the whole bill. HomeBuilding & Renovating's July 2026 guide lists typical professional and other costs:
- Architectural drawings: £1,500 to £4,000
- Structural engineer: £750 to £2,500
- Party wall surveyor: £1,000 to £2,500 or more, if needed
- Skip hire and waste removal: £300 to £600 per skip
- Fixtures and fittings: £2,000 to £15,000 or more
On top of those, a householder planning application in England costs £548 if you need one (Planning Portal, 2026), and building control charges vary by council or approver. Checkatrade suggests that extras like these can add 10–15% to a budget, and recommends keeping a contingency of around 10%.
What Pushes the Price Up or Down
- Size of the loft — bigger lofts need more materials, structure and labour.
- Type of conversion — rooflight conversions cost least; mansards cost most.
- Structural work — steel beams, roof alterations and a new staircase add significantly.
- Bathrooms and finishes — an en-suite, bespoke storage or high-end finishes raise the cost.
- Location — labour and materials tend to cost more in London and the South East.
- Access and complexity — tight access, older roofs and conservation-area requirements can all add cost.
How Long Does It Take?
Checkatrade's March 2026 guide puts a typical 30m² rooflight conversion at around 4–6 weeks on site, a dormer or hip-to-gable at around 10–12 weeks and a mansard at around 8–10 weeks, once any planning permission is in place. Allow extra time beforehand for design, approvals and any party wall notices.
Does a Loft Conversion Add Value?
It can. Checkatrade says a well-designed loft conversion can add up to around 20% to a property's value, depending on the location and what the conversion creates. That is not guaranteed — speak to a local estate agent about your street before relying on it, and don't assume the added value will exceed what you spend.
Paying for a Loft Conversion
Common routes include savings, remortgaging or further borrowing on your mortgage, and unsecured home improvement loans. Rates, limits and eligibility vary by lender, and borrowing against your home puts it at risk if you cannot keep up repayments. Speak to a qualified mortgage or financial adviser before borrowing.
Getting an Actual Price
Online ranges can only take you so far. To get a real price, a loft conversion specialist needs to see your loft, and it is sensible to compare more than one written quote. Better Lofts is an introduction service run by Better Home Hub Ltd: send us an enquiry and Better Home Hub will try to introduce you to a specialist who covers your area. It's free to use and there's no obligation. You can also read about the different loft conversion types.
