How much does a loft conversion cost in the UK?
A 2026 guide to loft conversion costs by type — Velux, dormer, hip-to-gable and mansard.
A loft conversion is one of the best ways to add space and value, and the price depends mostly on the type of conversion. Here are typical 2026 costs.
Typical loft conversion costs
| Type | Typical cost (2026 guide) |
|---|---|
| Velux (rooflight) conversion | £15,000–£30,000 |
| Dormer conversion | £35,000–£60,000 |
| Hip-to-gable conversion | £60,000–£70,000 |
| Mansard / L-shaped | £70,000–£100,000+ |
| Cost per square metre | £1,000–£2,500 / m² |
These are typical guide prices for 2026 and will vary by job, property and location. Always get written quotes for your own project before deciding.
What affects the cost?
- The type of conversion (Velux, dormer, hip-to-gable, mansard)
- Structural work, stairs and available head height
- The specification of the new room and any en-suite
- Planning, party-wall and building-control requirements
- Access and the age of the property
- London rates (15–25% above the national average)
Loft conversion costs in London
In London and the South East, expect to pay 15–25% more than in the north for the same conversion. Loft conversions are popular in London’s terraced housing, where they add valuable space without extending the footprint.
How to get a fair price
Get detailed, like-for-like quotes from more than one specialist, use a written contract with staged payments, and confirm who handles building control and any party-wall agreements. Check FMB or TrustMark membership.
Frequently asked questions
Which loft conversion is cheapest?
A Velux or rooflight conversion is usually the most affordable, from around £15,000–£30,000, because it works within the existing roofline. Dormer, hip-to-gable and mansard conversions cost more as they alter the roof structure.
Do I need planning permission for a loft conversion?
Many loft conversions fall under permitted development, but not all — mansard conversions and those in conservation areas often need permission. Building regulations always apply, and party-wall agreements are common on terraces.
How long does a loft conversion take?
A Velux conversion can take 4–6 weeks, a standard dormer 8–10 weeks, and larger hip-to-gable or mansard projects 10–14 weeks or more.
Planning a loft conversion?
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