How much does a loft conversion cost in the UK?

A loft conversion is one of the best ways to add a bedroom or office without losing garden space, and it often adds real value to a home. Prices depend mainly on the type of conversion and how much structural work is involved. Here is what a loft conversion typically costs across the UK in 2026.

Types and typical prices

• Rooflight (Velux): the simplest option, adding windows into the existing roofline, usually £25,000 to £40,000.
• Dormer: a box extension out from the roof for more headroom and floor space, roughly £35,000 to £60,000.
• Hip-to-gable: rebuilds a sloping side into a vertical gable wall to gain volume, about £45,000 to £70,000.
• Mansard: the biggest change to the roof shape, giving the most space at the highest cost.

What drives the cost

• The staircase. Fitting a new stair safely can eat into the room below and adds joinery.
• Structural steels. Most conversions need steel beams to support the new floor and roof.
• Dormer size. A bigger dormer means more structure, roofing and glazing.
• Ensuite. Adding a bathroom means plumbing, tiling and an extra trade.
• Finish. Standard versus premium fittings can swing the total significantly.

Planning and permitted development

Many loft conversions fall under permitted development and do not need full planning permission, but always check, especially in a conservation area or on a flat, where the rules differ. It is worth getting a lawful development certificate for peace of mind.

Building control

Whatever the type, a loft conversion needs building control sign-off. This covers the structure, fire safety, insulation and the staircase. Your builder or a private inspector will arrange the checks, and you get a completion certificate at the end.

How long does it take?

A typical loft conversion takes roughly 6 to 10 weeks, depending on the type and the weather. A simple rooflight job is at the shorter end, a mansard or hip-to-gable at the longer end.

How to compare quotes

• Get a detailed written quote covering structure, staircase, glazing and finish.
• Check what is included: building control fees, plastering, electrics and decoration.
• Compare two or three quotes on the same scope. (See questions to ask before hiring a builder.)
• Pay in stages tied to progress, never a large sum up front.

Find a trusted loft conversion specialist near you

You can find and compare loft conversion specialists and builders in your area on GotAPal. Read real reviews and message them directly. GotAPal is free to use and free to list, with no lead fees, ever.