Adding a single storey extension is one of the most efficient ways to increase your home’s floor area without moving. But what should you expect to pay? In this guide, we break down current single storey extension prices, what influences costs, and how to plan your budget with confidence.
Costs vary significantly depending on location, design, materials, and complexity. Here’s a breakdown of average prices per square metre:
| Specification Level | Typical Cost (per m²) | Notes |
|---|---|---|
| Basic Build | £1,200 – £1,500 | Plaster finish, no structural alterations |
| Mid-Range | £1,500 – £1,800 | Bi-fold doors, skylights, fitted kitchen |
| High-End | £1,800 – £2,500+ | Premium glazing, structural steelwork |
Total cost example (30m² mid-range extension): £45,000 – £54,000 (excluding VAT, professional fees, and external landscaping)
“A well-planned 30m² extension typically starts around £50,000 in most UK regions, but prices climb fast with bespoke glazing and internal finishes.”
More m² means more materials and longer build times. Complex layouts require extra groundwork and steel.
Removing external walls adds steelwork costs (£2,000–£4,000+). Drainage or sloped terrain increases groundwork time.
London and the South East typically command 15–25% higher build rates. Labour shortages and permit delays affect cost.
These are often excluded from “per square metre” quotes:
| Item | Typical Cost Range |
|---|---|
| Architect/Designer Fees | 8–12% of build cost |
| Planning Application | £200–£300 |
| Building Regulations | £500–£1,000+ |
| Structural Engineer | £500–£2,000 |
| Party Wall Agreements | £700–£1,500 per neighbour |
Case A – 25m² Rear Extension, Essex
Case B – 35m² Side/Rear Wraparound, Greater London
Most single storey extensions fall under Permitted Development rules if they meet certain limits:
Projects in conservation areas, flats, or larger builds may need full planning permission. Always confirm with your Local Planning Authority.
“Avoid assuming your extension is PD-compliant—get written confirmation. A lawful development certificate helps avoid problems during resale.”
A single storey extension typically adds ground-floor space to a property, often for:
It can run across the rear, side, or wrap around existing rooms. Most UK homeowners opt for between 20–40m² of extra space.
Single storey extension prices in the UK start from around £1,200 per square metre, but rise based on location, specification, and design complexity. Budget for design, approvals, and contingency on top of build cost.
A well-planned extension doesn’t just add floor area—it improves layout and long-term value.
Need advice on integrating daylight into your extension project?
Dakeas roof windows are engineered for performance, longevity, and cost efficiency. Speak to our technical team for help specifying the right glazing solution for your design.
Estimate your project cost. We use a fixed build rate of £1,500/m² and add 10% professional fees automatically.
Estimated total cost: £0.00
Are you a professional installer, contractor, or housebuilder? Sign up for our newsletter today to be the first to hear about new products, promotions and exclusive offers.
For all other enquiries please complete our contact form
on our website.