How much does a loft conversion cost?
This is the project where publishers disagree most. Checkatrade and the HomeOwners Alliance put a dormer conversion at £50,000; Rated People's dormer average is £90,000, nearly double. A Velux only conversion starts around £27,500, and large or complex conversions in London can pass £130,000.
£27,500 for a Velux conversion; £40,000–£120,000 for a dormer
The published figures
Every figure below is a published guide figure, shown as its publisher printed it and linked to the source. Retrieved on 2026-07-17.
| What | Published figure | Basis | Source |
|---|---|---|---|
| Velux conversion / dormer / hip to gable | £27,500 / £50,000 / £60,000 | Checkatrade cost guide (opens in new tab) | |
| Per square metre | £1,250–£2,500 per m² | HomeOwners Alliance guide (opens in new tab) | |
| UK average, all types | £55,000–£120,000, minimum from £45,000 | Resi cost guide (opens in new tab) | |
| Main dormer conversion, London | £56,163 | excluding VAT, glazing and fittings | Resi cost guide (opens in new tab) |
| Dormer conversion | £55,500–£118,400, average £90,000 | Rated People cost guide (opens in new tab) | |
| Dormer window / Velux window | £4,500–£6,500 / £900–£1,300 each | Resi cost guide (opens in new tab) | |
| Professional fees: structural engineer | £500–£1,000 | surveyor £500–£1,500, building regulations £700–£1,200 | Resi cost guide (opens in new tab) |
What moves the price
- Conversion type: Velux, dormer, hip to gable or mansard
- Size and number of windows
- Existing roof shape and structural complexity
- Stairs: a simple flight versus a bespoke one
- Professional fees: surveyor, structural engineer, building regulations, party wall
Get real quotes
Guide figures set expectations; only quotes set your price. Compare local businesses on their public evidence:
Sources
- Checkatrade cost guide (opens in new tab) (directory site, published 2026)
- HomeOwners Alliance guide (opens in new tab) (consumer body, published 2026)
- Resi cost guide (opens in new tab) (installer, published 2025-10)
- Rated People cost guide (opens in new tab) (directory site, published 2026)
Figures retrieved from the named sources above on 2026-07-17. Prices change; always confirm with quotes.
More ways to check who to trust
Free, independent checks. No ads, no paid placement.
- Trade Credential Guide
Which official register to check for each trade, and how to verify it.
- Cowboy Checker
Spot the warning signs of a dishonest business before you hire.
- Compare Quotes
Enter the names from your quotes and line them up on the public evidence.
- Company Health Check
Check whether the company behind a business is active, dissolved, or in liquidation.
- Certifications
The certifications, licences and registrations we have found in public sources, and what each one means.
- Do I Need Planning Permission?
Whether your project needs planning permission, with the rules cited and your council's real record.
- Paperwork Checker
The certificates your building work should have produced, and what to do if one is missing.
- Quote Check
Describe the quote you were given and see which features are officially listed warning signs.
- Rating Reality Check
Where a rating and review count really sit against the market's full distribution.
- Licence Check
A licence number from a van or quote, checked against every public register included here in one search.
- Gas and Electrical Rules
Gas Safe rules, England's notifiable electrical work, and the DIY the law actually allows.
- Emergency: Who to Call
Gas smell, power cut, burst pipe: the official number to call first, from the official pages.
- Planning Approval Times
How long planning permission really takes in your council, from its own register.
- Waste Carrier Check
If your rubbish is fly-tipped, the fine can be yours. The duty of care and the free check.
- Heat Pump Grant Checker
The published heat pump grant, who actually claims it, and whether the conditions cover you.
- Busy Season
When each trade is actually busiest, from the dates on real finished jobs.
- Before You Pay the Final Bill
Faulty work and a final bill: the Act's remedy ladder, stated honestly for both sides.
- VAT on Building Work
20%, 5%, 0%, or legitimately none at all: what the published VAT rules actually say.
- Council Experience
Which architects and agents know your local council.
- Planning Approval Rate
How often a firm's planning applications get approved.
- Planning Finder
Planning applications and the architects behind them, by postcode.