How Much Does a Loft Conversion Cost in 2026? UK Price Guide
Realistic UK loft conversion costs for 2026. Dormer, hip-to-gable, Velux and mansard — with itemised breakdowns, planning rules, and what affects the price.
What Does a Loft Conversion Actually Cost in the UK?
A loft conversion remains one of the smartest home improvements in the UK — adding a bedroom (often with en-suite), increasing your property value, and avoiding the hassle and cost of moving. Here’s what UK builders are actually charging in 2026.
Loft Conversion Cost Summary
| Type | Typical Cost (2026) | Added Floor Space | Planning Needed? |
|---|---|---|---|
| Velux (rooflight only) | £20,000 – £35,000 | 10–15 m² | Usually PD |
| Rear dormer | £35,000 – £55,000 | 15–25 m² | Usually PD |
| Hip-to-gable + rear dormer | £45,000 – £65,000 | 20–30 m² | Usually needs planning |
| L-shaped dormer | £45,000 – £65,000 | 20–30 m² | Usually PD |
| Mansard | £55,000 – £80,000 | 25–40 m² | Always needs planning |
Prices are for England outside London. London: add 25–40%.
Cost Breakdown: Typical Rear Dormer Loft Conversion
| Work Stage | Cost Range | % of Total |
|---|---|---|
| Structural steelwork (ridge beam, purlins) | £3,000 – £5,000 | 7–10% |
| Dormer construction (walls, roof, cheeks) | £8,000 – £12,000 | 18–24% |
| Staircase | £2,500 – £5,000 | 6–10% |
| Windows (Velux + dormer) | £2,000 – £4,000 | 5–8% |
| Insulation & boarding | £2,500 – £4,000 | 6–8% |
| First fix (plumbing, electrics) | £3,000 – £5,000 | 7–10% |
| Plastering | £2,000 – £3,500 | 5–7% |
| En-suite bathroom | £3,500 – £7,000 | 8–14% |
| Second fix & finishes | £2,500 – £4,000 | 6–8% |
| Decoration | £1,500 – £2,500 | 3–5% |
| Scaffolding | £1,500 – £2,500 | 3–5% |
| Building Regs & structural engineer | £1,500 – £2,500 | 3–5% |
| Total | £33,500 – £56,500 |
Types of Loft Conversion Explained
Velux (Rooflight) Conversion
The simplest and cheapest option. Roof windows are fitted into the existing roof slope with no change to the roof structure. Best for lofts with existing good headroom (minimum 2.2m at the ridge).
Rear Dormer
A flat-roofed box structure is built out from the rear roof slope, creating a room with full standing headroom. The most popular type in the UK because it maximises space and usually falls under Permitted Development.
Hip-to-Gable
The sloped side wall (hip) of the roof is built up to a vertical gable wall, then a rear dormer is added. Common on semi-detached and detached houses with hipped roofs. Usually needs planning permission.
L-Shaped Dormer
Two dormers built at right angles, creating an L-shaped room that spans the full width and depth of the roof. Common on Victorian and Edwardian terraces.
Mansard
The entire roof profile is changed — the existing roof is replaced with near-vertical walls and a flat top. Creates the most space but is the most expensive and always requires planning permission.
What Affects the Price?
Your Existing Roof
- Trussed roof (W-shaped trusses): Needs significant structural work — steel beams to replace the trusses. Adds £3,000–6,000 vs a traditional cut-roof.
- Cut roof (individual rafters and purlins): Easier to convert, less structural work needed.
Staircase Position
The staircase needs to rise over an existing room below. If it can go over the existing stair (the most common position), that’s cheapest. If it needs to steal space from a bedroom, the project gets more complex.
En-Suite vs No En-Suite
An en-suite shower room adds £3,500–7,000 but significantly increases the usability and resale value. Plumbing is usually routed down through the floor to connect to the existing soil stack.
Fire Regulations
Building Regulations require a protected escape route from the loft to the front door. This usually means:
- Fire doors on all rooms opening onto the stairway
- Mains-wired smoke detectors on each floor
- 30-minute fire-resistant boarding to the stairway (if open plan below, this can get expensive)
Regional Price Variations
| Region | Dormer Conversion Cost |
|---|---|
| London | £45,000 – £70,000 |
| South East | £40,000 – £60,000 |
| South West | £35,000 – £50,000 |
| Midlands | £32,000 – £48,000 |
| North | £30,000 – £45,000 |
| Scotland | £30,000 – £48,000 |
| Wales | £28,000 – £42,000 |
Is a Loft Conversion Worth It?
On average, a loft conversion adds 15–20% to a property’s value:
| Property Value | Conversion Cost | Value Added (17.5%) | Net Gain |
|---|---|---|---|
| £250,000 | £45,000 | £43,750 | −£1,250 |
| £350,000 | £45,000 | £61,250 | +£16,250 |
| £450,000 | £50,000 | £78,750 | +£28,750 |
| £600,000 | £55,000 | £105,000 | +£50,000 |
The higher your property value, the better the return. In areas with high house prices (London, South East), loft conversions almost always pay for themselves and more.
How to Get an Accurate Loft Conversion Quote
Every loft is different. For an accurate quote you need:
- A measured survey — a builder or surveyor assesses headroom, roof structure, and access
- Structural engineer’s report — determines what steelwork is needed
- Specification decisions — en-suite layout, window choices, staircase design, finish level
EasyEstimate helps builders produce itemised loft conversion quotes with live UK material prices and 140+ built-in calculators for every element — from steelwork to bathroom tiling.
Get a professional loft conversion estimate → | Price it yourself with our software →
Related Resources
- House Extension Cost Guide — full extension pricing breakdown
- Builders Quote Template — how to structure a professional building quote
- Roofing Calculator — calculate roof tiles and materials
- Plastering Calculator — calculate plaster for new rooms
- Construction Estimating Software — price any project with live UK costs
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