How much does a loft conversion cost in 2026?
A loft conversion in the UK typically costs £30,000 to £45,000 for a rooflight conversion, £50,000 to £90,000 for a rear dormer, £60,000 to £95,000 for a hip-to-gable with dormer and £65,000 to £110,000 for a mansard, including VAT. The type of roof you have decides which conversion is possible.
How much does each type of loft conversion cost?
| Conversion | Typical cost incl. VAT | Time on site |
|---|---|---|
| Rooflight (Velux-style) | £30,000 to £45,000 | 6 to 8 weeks |
| Rear dormer | £50,000 to £65,000 | 8 to 12 weeks |
| Full-width dormer with en-suite | £60,000 to £80,000 | 8 to 12 weeks |
| Hip-to-gable with dormer | £60,000 to £80,000 | 9 to 13 weeks |
| Mansard | £65,000 to £85,000 | 10 to 14 weeks |
What affects the cost of a loft conversion?
- Head height. About 2.2 m from the top of the ceiling joists to the underside of the ridge is the usual minimum before the roof needs raising.
- Roof shape. Hipped roofs need a hip-to-gable rebuild; modern trussed roofs need more steel to open up.
- Bathroom. An en-suite adds plumbing, waste routes and tiling.
- Fire safety. A protected escape route often means new fire doors and linked smoke alarms on the floors below.
- Party walls. Steels bearing on a shared wall usually need party wall notices in England and Wales.
Is a loft conversion worth it?
A loft conversion usually adds a bedroom and bathroom for less than the cost of moving, without losing garden space. Whether it adds more value than it costs depends on local house prices, so it is worth asking a local estate agent for a view before committing.
Do I need planning permission for a loft conversion?
In England many loft conversions are permitted development, provided the extra volume stays within 40 m³ on a terraced house or 50 m³ on a semi or detached house, nothing goes above the existing ridge, and no dormer faces a road on the main elevation. Mansards and front dormers usually need planning permission. See our loft permitted development guide for the detail.
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This guide is general information about building work in the UK, not legal or tax advice. Rules change, so check the current position for your property with the council, HMRC or a qualified adviser before relying on it.