How Much Does a Loft Conversion Cost Per m² in 2026 UK?
In 2026, UK loft conversions cost £1,250–£2,800 per m² depending on type. Velux (rooflight only) conversions sit at £1,250–£1,750/m², rear dormers at £1,650–£2,300/m², L-shape and hip-to-gable at £1,800–£2,500/m², mansards at £2,000–£2,800/m². London adds 18–25%, the North discounts 10–15%. Total project cost lands at £35,000–£95,000 for a typical 25–40 m² conversion.
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.
Loft conversion £/m² in 2026 — at a glance
2026 UK average rate per m² (mid-tier finish, mid-range region):
- Velux conversion: £1,250–£1,750/m² (no roof shape change)
- Rear dormer: £1,650–£2,300/m² (most common in UK)
- Hip-to-gable: £1,750–£2,400/m² (semi-detached / detached only)
- L-shape (rear + side): £1,800–£2,500/m² (Victorian / Edwardian terraces)
- Mansard: £2,000–£2,800/m² (full roof shape change)
For a typical 30 m² useful floor area in 2026, total project cost lands at: Velux £38–52k, dormer £50–69k, hip-to-gable £53–72k, L-shape £54–75k, mansard £60–84k. London inner-zone postcodes add 18–25% across the board; the North and Wales discount 10–15%.
What's actually inside the £/m² figure?
The headline rate per m² covers the full turn-key build, not just the structural shell. Here's the indicative breakdown for a typical £1,950/m² mid-tier dormer conversion in 2026.
Loft conversion £/m² by UK region (rear dormer)
3 things that swing the rate £300–£500/m²
1. Whether you add an en-suite
Adding a bathroom adds £7,000–£12,000 to a typical conversion regardless of total floor area, so on a small 22 m² conversion the en-suite alone pushes the headline £/m² up by £320–£550. Many quotes lump this in but base their square-metre figures on conversions without en-suites — always check what's included.
2. Existing roof structure (truss vs cut-roof)
Pre-1965 "cut" roofs with traditional rafters and purlins are typically £150–£250/m² cheaper to convert than 1970s–2000s trussed-rafter roofs. Trussed roofs need £5,000–£12,000 of new structural work to remove the truss webs without compromising load paths. If you can, check your roof type before getting quotes — the difference can be substantial.
3. Finish tier (entry / mid / premium)
Entry-tier finishes (B&Q-bracket bathroom suite, vinyl flooring, basic carpets, no tongue-and-groove) sit at the low end of our £/m² ranges. Premium-tier (Quooker tap, porcelain tiles, oak engineered floor, bespoke joinery) can add 25–40% on top. Most quotes default to mid-tier — ask explicitly for the spec sheet to know what you're buying.
Worked example: 32 m² rear dormer in Manchester
1930s 3-bed semi in South Manchester. Owner wants a 32 m² rear dormer creating master bedroom + en-suite with walk-in shower. Existing pre-WW2 cut-roof structure (favourable). Property has a 2.45m clear ridge under existing rafters.
Illustrative quote for this scenario: £58,500 ex-VAT (£70,200 incl. VAT). Per-m² rate: £1,830/m² — in line with the North-West mid-range expected band.
Inclusions: architect drawings + LDC application, building regs, structural engineer, party wall agreement, full bedroom + en-suite fit-out (mid-tier suite, porcelain tiles, walk-in shower with thermostatic mixer), stairs alteration with new oak handrail, 4 Velux windows, 1 large flat-roof rear dormer with cladding finish.
Verdict: reasonable mid-tier price for the region. Owner's main risk is the en-suite tile choice (overspending here adds £2k–£5k easily) and the dormer cladding choice (cheap zinc-look uPVC dates fast; standing-seam zinc is the durable mid-tier choice). Builder is bonded under FMB warranty. Build window: 13 weeks.
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Frequently asked questions
Velux (rooflight only) conversions at £1,250–£1,750/m² are the cheapest because they don't change the roof shape. The catch is they're only viable if your existing loft already has the head height; you can't gain head height with a Velux. For most UK semis with marginal head height, a rear dormer at £1,650–£2,300/m² is the more realistic option.
Mansards rebuild the entire roof shape with a steeply pitched lower section and near-flat top. The structural complexity, scaffolding scope, planning application, and roofer time all add cost. They typically deliver the most usable floor area, so on a per-m² basis the premium is partially offset — but headline cost is always highest.
Most builders quote ex-VAT for B2C extension work and add 20% on top — always confirm. A small number of conversions qualify for 5% reduced VAT (e.g. converting a property that has been empty 2+ years). For the standard owner-occupier loft conversion, expect 20% VAT on the full quote.
The £/m² figure is useful for ballpark planning and to sanity-check a quote. Always go to a fixed quote with detailed scope-of-works before signing. Per-m² rates can hide £5,000–£12,000 of variations on items like en-suite spec, bespoke joinery, stair-removal complexity, and window upgrades.
You can save 8–12% in theory by trade-managing yourself, but the risk is high — sequencing errors and dispute resolution typically eat the saving. Most homeowners who try regret it by week 6. Stick with a single main contractor on a JCT or FMB-warranty contract for projects over £30,000.
Loft conversions typically run £300–£600/m² cheaper than equivalent ground-floor rear extensions, because there's no foundation work and limited groundworks. The catch: useful floor area is smaller (sloped ceilings reduce effective space by 12–20%). Rear extensions deliver more open-plan space; loft conversions deliver bedrooms.
Sources used in our 2026 figures
- FMB — Federation of Master Builders House Survey — UK loft conversion build-cost benchmarks and member quote averages
- BCIS — Building Cost Information Service — RICS-backed rates database for UK construction projects
- ONS — Producer Price Inflation — Materials cost trends through 2026
- MHCLG — Permitted Development Rights for Householders — Volume limits affecting design choices and therefore cost
Methodology note: Per-m² rates use BestBuilders' 2026 regional cost model (national cost guides × regional labour index). Regional adjustments derived from BCIS regional building-cost indices for residential conversions. Mid-tier finish assumed unless stated.