Converting your loft is one of the most popular ways to add an extra bedroom or home office to your property without losing garden space. Not only does it expand your living area, but an expert loft conversion can also increase your property value by up to 20%.
In this comprehensive 2026 guide, we outline average loft conversion costs in the UK by type (Velux, Dormer, Hip-to-Gable, Mansard), associated professional fees, and how to connect with verified specialist loft builders on GetBuilder.
Average loft conversion costs by type in 2026
The construction method and whether you choose to extend your roofline are the primary drivers of your budget. Below is an overview of standard average prices for typical loft conversion styles in the UK:
| Conversion Type | Key Features | Average Cost Range |
|---|---|---|
| Velux (Rooflight) | Standard roof windows, no structural alterations to roofline, quickest build | £22,500 - £32,000 |
| Dormer Loft | Box extension built out of the roof slope, creates standing headroom, very popular | £40,000 - £60,000 |
| Hip-to-Gable | Straightens the sloping side wall of a hip roof into a gable wall, adds stair space | £50,000 - £75,000 |
| Mansard Loft | Completely changes the roof structure with a flat roof and almost vertical rear wall | £60,000 - £85,000+ |
Professional fees to budget for
A loft conversion is a complex structural project. Before hiring a builder, you should budget for the following professional services:
- Architect Fees: £1,000 - £2,500 for design plans, layout options, and structural drawings.
- Structural Engineer: £500 - £1,200 to calculate the size of steel support beams (RSJs) required to support the new floor.
- Building Control & Planning Permission: Standard building regulations approval fees typically range from £500 to £900. Note that most dormer and Velux conversions fall under Permitted Development, meaning they don't require full planning permission.
- Party Wall Agreements: If you have a terraced or semi-detached home, you must notify your neighbors. A party wall surveyor costs around £1,000 to £2,000 per neighbor if a dispute arises, or £0 if they sign the consent form directly.
Key items that increase loft conversion costs
- Adding an En-suite: Incorporating a bathroom/toilet adds £8,000 to £15,000 to your builder's estimate due to plumbing complexity, sanitaryware, tiling, and pump installations.
- Stairs location: Creating a permanent staircase from the first floor to the new loft requires space. If you need to lose a storage cupboard or slice a corner out of an existing bedroom, structural work will increase labor costs.
- Roof height lift: Standard building regulations require a minimum head height of 2.2 metres in the highest part of the loft. If your existing loft height is lower, your contractor must lift the roof tiles or lower the first-floor ceilings, adding £10,000 to £20,000 to the cost.
How to get accurate loft conversion quotes on GetBuilder
To ensure your project runs smoothly and complies with structural regulations, follow these guidelines when hiring:
- Always use structural drawings: Requesting builder quotes without architect designs or engineer steel calculations will result in inaccurate pricing.
- Check certificates: Verify the builder is insured and has previous checked reviews for structural renovations.
- Use GetBuilder: Post your project details for free on GetBuilder to connect with verified loft conversion builders. Compare profiles, inspect past work photos, and hire safely with checked reviews.
