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 loft conversion specialists.
Planning the work? Check what it usually costs, or work out your own estimate. The free quote form is at the top of this page.
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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.
Dormer Loft Conversion Cost FAQs
Get Free Loft Conversion Quotes from Vetted Specialists
BestBuilders matches you with up to 3 vetted local loft conversion specialists. Ask each one for current public liability cover and their building control route before you choose — all for free.
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Dormer — guides and detail
The detail behind the number: what changes the price, the planning position, and how to check a quote before you accept it.
Registered members: Loft Conversions
11 businesses offering loft conversions have a public profile with BestBuilders. Each listing is a business that registered with us directly; the details shown are the ones it declared at registration, and a Companies House number appears only where one was given.
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