If you’re planning to extend your home, the first thing you want to know is: how much will it cost per metre square? The short answer in the UK for 2025 is around £2,000 to £3,000 per m² for a typical single-storey extension of decent quality, while high-end finishes or tricky sites can push the figure beyond £3,500 per m². According to specialist data from Buon Construction, a ground-floor rear extension averaged about £2,890 per m², and a double-storey rear extension around £2,399 per m².
Table of Contents
What Affects the Cost Per m²?
1. Size & type of the extension
A large single-storey rear extension spreads fixed costs (foundation, roof) over more m² so the cost per m² may drop slightly. A two-storey or complex wrap-around design costs more because of extra structural work. For example, two-storey may cost only 50-70 % more than a single storey but adds more space.
2. Location in the UK
Labour and materials cost more in London and the South East. For example one guide puts London single-storey extension cost at £2,500-£4,000 per m².
3. Quality of Finishes & Specification
For the basic extensions including the standard doors, windows, and flooring, the cost is usually less. On the other hand, the premium extensions that include large glazing, customised joinery, and ceilings can raise the overall cost.
- Standard quality: ~£2,200-£2,500 per m²
- Good quality: ~£2,500-£2,900 per m²
- Excellent quality: £2,900-£3,300 per m²
4. Site Conditions & Structural Work
If the extension needs deep foundations, underpinning, complex drainage, party-wall work or tricky access, cost per m² rises. Standard cost guides often exclude large structural surprises.
5. Professional Fees, Approvals & VAT
Architect drawings, planning or building-regulation fees, structural engineers, and VAT (20% in the UK) can add 10-15% or more to the cost of construction per m². Although various professionals don’t include fees, only the building cost is included.
Updated Cost Estimates for 2025 – UK Average
Here’s a simple table summarising the cost per m² by type and quality:
Updated Cost Estimates for House Extensions in the UK (2025)
Here are updated tables showing realistic cost-bands per m² for standard builds, slightly below some competitor averages to reflect conservative budgeting.
Single-Storey (Ground Floor) Rear Extension – Standard Finish (~£2,450-£3,050/m²)
| Region | Low Budget | Mid Budget | High Budget | Approx Cost per m² (Low) | Approx Cost per m² (Mid) | Approx Cost per m² (High) |
| East Anglia | £75,000 | £81,500 | £88,000 | £2,500 | £2,700 | £2,900 |
| London | £80,000 | £89,000 | £98,000 | £2,650 | £2,900 | £3,200 |
| Midlands | £73,000 | £80,000 | £87,000 | £2,450 | £2,700 | £2,950 |
| North England | £71,000 | £77,000 | £83,000 | £2,400 | £2,650 | £2,900 |
| Wales | £71,000 | £79,000 | £85,000 | £2,400 | £2,650 | £2,850 |
| UK Average | £77,000 | £85,000 | £92,500 | £2,550 | £2,800 | £3,050 |
Double-Storey Rear Extension – Standard Finish (~£2,050-£2,650/m²)
| Region | Low Budget | Mid Budget | High Budget | Approx Cost per m² (Low) | Approx Cost per m² (Mid) | Approx Cost per m² (High) |
| East Anglia | £125,000 | £137,000 | £148,000 | £2,100 | £2,300 | £2,500 |
| London | £135,000 | £150,000 | £166,000 | £2,250 | £2,500 | £2,800 |
| Midlands | £122,000 | £135,000 | £146,000 | £2,050 | £2,300 | £2,550 |
| North England | £119,000 | £130,000 | £142,000 | £2,000 | £2,250 | £2,450 |
| Wales | £120,000 | £136,000 | £146,000 | £2,030 | £2,300 | £2,500 |
| UK Average | £128,000 | £142,000 | £155,000 | £2,150 | £2,400 | £2,650 |
These estimates are for standard specification builds and exclude premium finishes, extensive structural changes or VAT.
What to Expect When Working with Buon Construction
Our local specialist, Buon Construction, offers full-service house extensions across Nottingham and the surrounding areas. They cover design, planning, help, construction, and finishing.
Here’s what this means for your budget:
- Using a local contractor means fewer surprises with local labour/materials and compliance with UK regulations.
- Because they handle full project management, your cost per m² may sit towards the standard band (not the lowest budget) because quality, oversight and finishing matter.
- Buon handles everything: single-storey, double-storey, loft & garage conversions, so you have flexibility and fewer subcontractors to coordinate.
Tip: When you get a quote from them, ask to see the cost per m² broken down by area, finish level and exclusions (e.g., doesn’t include high-end kitchen or landscaping).
Budget Checklist – Things to Ask Before You Commit
- What cost per m² is being used and which finish level is it assuming?
- Does the quote include professional fees (architect/engineer), planning approval, building-regulation compliance?
- Is VAT and any contingency included (e.g., 10 % extra for unforeseen costs)?
- What are the site conditions (access, ground quality, party wall)?
- Are fixtures and fittings included or is that extra?
- What timeline is expected and how could delays affect cost?
- What level of finish is assumed (doors, windows, insulation, heating)?
- If you choose premium finishes, how will cost per m² change?
| Fact | Value |
| Typical UK cost per m² (standard single-storey) | £2,000-£2,500 |
| Premium cost per m² in London/complex cases | £2,500-£4,000+ |
| Double-storey cost per m² range | £1,650-£3,250 |
| Professional/fee contingency to plan | ~10-15 % extra |
| Local contractor example | Buon Construction (Nottingham-based) |
Final Takeaway
If you’re planning a home extension in the UK in 2025, budget around £2,000-£3,000 per m² for a typical single-storey extension with decent finishes. If you’re going premium, in London, or doing double-storey with complex structure, expect £3,000-£4,000+ per m². Using a company like Buon Construction brings a full-service experience, but you still need to check what’s included. Do your homework with the checklist above, and you’ll avoid nasty cost surprises.
