Up-to-date extensions & conversions prices for 2026 — low, average and high UK rates for 6 common jobs, plus what affects the price and how to hire well.
Whether you are planning a rear extension, a loft conversion, a garage conversion or a full renovation, the builder you choose determines whether the project runs to time and budget — or becomes a source of stress. A good general builder coordinates groundwork, brickwork, structural alterations and the follow-on trades, acting as the backbone of any significant project. HireTrades helps you find established local builders with verifiable track records.
| Service | Low | Average | High |
|---|---|---|---|
Single storey extension per m² | £1,500 | 2,000 | £2,500 |
Double storey extension per m² | £1,800 | 2,300 | £2,800 |
Loft conversion complete | £35,000 | 52,500 | £70,000 |
Garage conversion complete | £10,000 | 15,000 | £20,000 |
Conservatory complete | £8,000 | 14,000 | £20,000 |
Garden room/office complete | £15,000 | 25,000 | £35,000 |
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As a guide, single-storey extensions in the UK cost £1,800–£2,800 per square metre depending on region and specification, so a 20m² extension typically lands between £36,000 and £56,000 before VAT. Loft conversions range from £25,000 for a simple roof-light conversion to £60,000+ for a dormer with en-suite. Garage conversions are usually £8,000–£20,000. Day rates for a builder and labourer team are typically £300–£450.
Before hiring a builder, ask to visit or see photos of at least two completed projects similar to yours. Confirm they hold public liability insurance (£1m minimum, £2m preferred) and ask whether they will manage building control sign-off. For structural work you will need calculations from a structural engineer — a professional builder will be comfortable working from these drawings. Agree a staged payment schedule tied to milestones rather than paying large sums up front, and get everything in writing including start date, duration and what happens with variations.
Builders on HireTrades carry public review histories from verified customers, so you can see how they performed on real projects — communication, tidiness, timekeeping and quality. Post your project for free, compare detailed quotes and speak to several builders before committing. For larger projects, that comparison regularly saves homeowners thousands of pounds.
In 2026, single storey extension typically costs between £1,500 and £2,500 (per m²) in the UK, with an average of around £2,000. Prices in London and the South East tend to sit at the higher end. Get multiple quotes from verified local professionals on HireTrades to find the best price for your job.
In 2026, double storey extension typically costs between £1,800 and £2,800 (per m²) in the UK, with an average of around £2,300. Prices in London and the South East tend to sit at the higher end. Get multiple quotes from verified local professionals on HireTrades to find the best price for your job.
In 2026, loft conversion typically costs between £35,000 and £70,000 (complete) in the UK, with an average of around £52,500. Prices in London and the South East tend to sit at the higher end. Get multiple quotes from verified local professionals on HireTrades to find the best price for your job.
In 2026, garage conversion typically costs between £10,000 and £20,000 (complete) in the UK, with an average of around £15,000. Prices in London and the South East tend to sit at the higher end. Get multiple quotes from verified local professionals on HireTrades to find the best price for your job.
Guides tell you the range — real quotes tell you your price. Post your job free and compare offers from verified local builders.