How Much Does a Dormer Loft Conversion Cost in 2026?
Real 2026 UK prices: rear dormer £45,000–£65,000, full-width £55,000–£80,000, hip-to-gable + dormer £65,000–£95,000. £2,200–£3,000 per m² typical — the highest value-add loft conversion type. Free quotes from vetted local specialists.
Do you need planning permission for a dormer?
Most rear dormers fall under Permitted Development if under 50m³ (40m³ on terraced houses) and not on the principal elevation. Article 4 areas, conservation areas and any front-facing dormer typically need full planning consent.
Read the dormer planning rules →Dormer Loft Conversion Cost at a Glance
Real cost ranges from BestBuilders data across 519 UK towns. Use these as your benchmark — then get 3 local quotes for your exact roof.
Adds one bedroom + en-suite (15–22 m²). 8–10 weeks on site. Usually permitted development on detached, semi and end-terrace roofs.
Get quotes →Spans the full rear roof: 25–35 m² of usable space. Typically two bedrooms or master suite. 10–12 weeks on site.
Get quotes →Replaces hipped slope with vertical gable, then adds rear dormer. Adds 35–50 m². 12–14 weeks on site. Often delivers 20–25% house value uplift.
Get quotes →Cost Per m² (UK 2026)
| Specification | Cost per m² | What's included |
|---|---|---|
| Basic — bedroom only | £2,200 – £2,500 | Steel beams, dormer build, insulation, plasterboard, electrics, basic flooring, decoration |
| Mid — bedroom + en-suite | £2,500 – £2,800 | Above + plumbing, en-suite shower room, wardrobe joinery, mid-spec finishes |
| High — master suite | £2,800 – £3,200+ | Bespoke joinery, premium en-suite, dressing area, AV pre-wire, premium finishes |
Dormer per-m² is higher than basic rooflight (Velux) loft conversions (£1,400–£1,800/m²) because of the additional structural work, but delivers significantly more usable floor area.
Dormer Loft Conversion Cost by Region
| Region | Single rear dormer | Full-width dormer | Hip-to-gable + dormer |
|---|---|---|---|
| London | £58,500 – £84,500 | £71,500 – £104,000 | £84,500 – £123,500 |
| South East | £53,100 – £76,700 | £64,900 – £94,400 | £76,700 – £112,100 |
| Midlands & SW | £42,800 – £61,800 | £52,300 – £76,000 | £61,800 – £90,300 |
| North & Yorkshire | £40,500 – £58,500 | £49,500 – £72,000 | £58,500 – £85,500 |
| Scotland, Wales & NI | £38,300 – £55,300 | £46,800 – £68,000 | £55,300 – £80,800 |
Dormer Loft Hidden Costs
Most builder quotes price the loft shell only — there's a layer of project costs that catches first-time loft converters out.
📐 Architect & structural engineer
Required for steel calcs, building control drawings and any planning application. A technician + SE combo is the cost-effective choice on standard rear dormers.
📋 Building regulations fees
Required for every loft conversion. Building control submission and 4–6 inspection visits as work progresses.
🏗 Party wall surveyors
Almost certainly needed on terraces and semis when steels rest on the party wall. Each dissenting neighbour means appointing a surveyor — typically you cover both sides.
🚿 Bathroom & en-suite fit-out
First-fix plumbing is often included; final fixtures, tiles, shower screens and accessories are usually separate. Pump for high-level shower runs another £500–£900.
🪜 Staircase & finishes upgrades
Standard MDF stairs are normally included. Bespoke oak with glass balustrade, premium handrails or matching landing finishes are extras worth costing in early.
📊 Contingency (always include)
Surprises happen — undersized joists, hidden wiring, unexpected steels. Industry standard 10–15% of total budget for loft work.
Dormer Loft Conversion Costs by Town
Each town page shows local loft specialists, town-specific cost ranges, recent project examples and nearby areas. Compare 3 free quotes from vetted local loft specialists.
Get Accurate Quotes for Your Dormer Loft Conversion
Online guides give you a benchmark — accurate pricing requires a specialist who has surveyed your roof. BestBuilders matches you with up to 3 vetted local loft specialists for free.