How Much Does a Loft Conversion Cost in 2026? Complete UK Guide
A loft conversion in the UK costs between £20,000 and £65,000 depending on the type. This complete guide breaks down costs for Velux, dormer, mansard, and hip-to-gable conversions with regional price variations and what affects your quote.
Better Home Hub Editorial Team
TL;DR: A loft conversion in the UK costs £20,000-£65,000 in 2026. Velux/rooflight conversions are cheapest (£20,000-£35,000), dormers cost £30,000-£50,000, and mansard conversions cost £45,000-£65,000. Most add 10-20% to your property value. Most don't need planning permission under permitted development rights.
Last updated: April 2026
Loft Conversion Costs at a Glance
| Type | Cost Range | Best For | Planning Permission? |
|---|---|---|---|
| Velux / Rooflight | £20,000 - £35,000 | Budget conversions, simple rooms | Usually not required |
| Rear Dormer | £30,000 - £50,000 | Maximum headroom, most popular | Usually not required |
| Hip-to-Gable | £35,000 - £55,000 | Semi-detached & detached homes | Usually not required |
| L-Shaped Dormer | £40,000 - £60,000 | Victorian terraces, maximum space | May be required |
| Mansard | £45,000 - £65,000 | Maximum space, flat-roof properties | Usually required |
What Affects the Cost of a Loft Conversion?
1. Type of Conversion
The conversion type is the biggest cost factor. A Velux conversion uses the existing roof structure, keeping costs low. A dormer extends the roof outwards to create more headroom and floor space. A mansard replaces the roof slope entirely, creating a near-vertical wall — the most expensive but most spacious option.
2. Property Size and Location
Larger properties cost more due to increased materials and labour. Location matters significantly:
- London & South East: 20-30% above national average
- South West & East of England: 5-10% above average
- Midlands: Around the national average
- North of England, Scotland, Wales: 5-15% below national average
3. Structural Requirements
Most loft conversions need structural steelwork (RSJs) to support the new floor. This typically costs £1,500-£3,000 for materials and installation. If your roof timbers need reinforcing or the existing floor joists are inadequate, additional structural work adds £2,000-£5,000.
4. Staircase
A standard straight staircase costs £1,500-£3,000. Space-saving designs or spiral staircases cost £2,500-£5,000. The staircase position affects the usable space on both the existing floor and the new loft floor.
5. Bathroom or En-Suite
Adding a bathroom to a loft conversion adds £3,000-£8,000 to the total cost. A shower room is cheaper than a full bathroom with bath. Plumbing in the loft is more complex and costly than ground-floor installations.
6. Windows and Glazing
Velux roof windows cost £500-£1,500 each installed. Dormer windows cost £1,500-£3,000 each. Juliet balconies add £1,000-£2,000. The number and size of windows significantly affect light, ventilation, and the overall cost.
Cost Breakdown: What's Included in a Quote
| Item | Typical Cost |
|---|---|
| Structural steelwork (RSJs) | £1,500 - £3,000 |
| Floor reinforcement | £1,000 - £2,000 |
| Staircase | £1,500 - £5,000 |
| Insulation (to Building Regulations) | £1,000 - £2,000 |
| Electrics (lighting, sockets) | £1,500 - £3,000 |
| Plastering and finishing | £2,000 - £4,000 |
| Fire safety (fire doors, alarms) | £500 - £1,500 |
| Scaffolding | £500 - £1,500 |
| Building Regulations application | £200 - £500 |
| Architect/structural engineer fees | £1,500 - £3,000 |
Do You Need Planning Permission?
Most loft conversions fall under permitted development rights and do not need planning permission, provided:
- The extension does not exceed 40m³ for terraced houses or 50m³ for detached/semi-detached
- The materials are similar in appearance to the existing house
- No extension is higher than the existing roof
- Side-facing windows are obscure-glazed and non-opening below 1.7m
- The property is not in a conservation area, National Park, or AONB
You will need planning permission for: mansard conversions, any increase in roof height, properties in conservation areas, listed buildings, and flats.
All loft conversions require Building Regulations approval regardless of whether planning permission is needed. This ensures fire safety, structural integrity, insulation, and staircase design meet legal standards.
How Much Value Does a Loft Conversion Add?
According to estate agents and RICS surveyors, a loft conversion typically adds 10-20% to a property's value. The value added depends on:
- Extra bedroom with en-suite: Adds the most value (15-20%)
- Home office or study: Adds 10-15%, especially post-pandemic
- Open-plan living space: Adds 5-10%
On a £300,000 property, a loft conversion costing £35,000-£45,000 could add £45,000-£60,000 in value — a strong return on investment.
Regional Price Guide
| Region | Velux | Dormer | Mansard |
|---|---|---|---|
| London | £28,000 - £45,000 | £40,000 - £65,000 | £55,000 - £85,000 |
| South East | £25,000 - £40,000 | £35,000 - £55,000 | £50,000 - £70,000 |
| South West | £22,000 - £36,000 | £32,000 - £50,000 | £48,000 - £65,000 |
| Midlands | £20,000 - £33,000 | £30,000 - £48,000 | £45,000 - £62,000 |
| North of England | £18,000 - £30,000 | £28,000 - £45,000 | £42,000 - £58,000 |
| Scotland | £18,000 - £32,000 | £28,000 - £48,000 | £42,000 - £60,000 |
| Wales | £18,000 - £30,000 | £27,000 - £44,000 | £40,000 - £58,000 |
How to Get the Best Price
- Get at least 3 quotes — prices vary significantly between builders
- Check qualifications — look for Federation of Master Builders members or NHBC-registered builders
- Avoid the cheapest quote — the lowest price often means corners will be cut on structural work or insulation
- Ask about guarantees — reputable builders offer 10-year structural guarantees
- Time your project — autumn and winter are typically less busy, so you may get better prices
- Consider a Party Wall survey early — if you share a wall, budget £700-£1,000 per neighbour for a Party Wall surveyor
Case Studies
3-Bed Semi in Leeds — Dormer Loft Conversion
Cost: £38,500 | Duration: 7 weeks
A rear dormer conversion creating a master bedroom with en-suite shower room. Included structural steelwork, staircase from existing landing, 2 Velux windows, full insulation, and Building Regulations sign-off. Added an estimated £55,000 to the property value.
4-Bed Detached in Surrey — Mansard Conversion
Cost: £58,000 | Duration: 10 weeks
Full mansard conversion creating two additional bedrooms and a family bathroom. Required planning permission due to the change in roof profile. Included architect fees, structural engineer, and Party Wall agreement with one neighbour. Added an estimated £95,000 to the property value.
Next Steps
Ready to explore a loft conversion for your home? Get free, no-obligation quotes from trusted local builders through Better Home Hub. Tell us about your property and we'll connect you with experienced loft conversion specialists in your area.
