# How Much Does a House Extension Cost in 2026? > What a single or double-storey extension really costs in the UK in 2026 — per square metre, by type, and the hidden costs to budget for. Source: https://renomate.co.uk/blog/house-extension-cost-guide --- # How Much Does a House Extension Cost in 2026? 5 March 2026 · 7 min read What a single or double-storey extension really costs in the UK in 2026 — per square metre, by type, and the hidden costs to budget for. ## Typical UK extension costs in 2026 **Most house extensions cost between £20,000 and £70,000 in 2026, or roughly £1,800–£3,000 per square metre.** A single-storey extension typically runs £20,000–£45,000; a double-storey adds far more floor area for a smaller jump, around £45,000–£90,000; and a large kitchen-diner or wrap-around at the top end can exceed £100,000. ## What drives the price Size and finish matter most, then groundworks, structural steel, glazing (bifolds and rooflights are pricey), and whether you’re moving a kitchen or bathroom into the new space. London and the South East sit well above the national average. ## Don’t forget the extras Beyond the build, budget for design and structural drawings, planning or building-regs fees, party-wall agreements with neighbours, and VAT. A sensible rule is to add 10–15% contingency on top of the quote. ## Single vs double storey — which is better value? A double-storey extension usually costs only around 50% more than a single-storey but can double the added floor space, so the cost per square metre is often lower. If your plot and budget allow, it’s frequently the better long-term value. ## Get a real figure for your home Costs vary hugely by design and region. [Share your plans](https://renomate.co.uk/enquire) and we’ll match you with vetted local [extension builders](https://renomate.co.uk/renovations/home-extensions) for accurate, no-obligation quotes. ## Frequently asked questions ### How long does an extension take to build? Most single-storey extensions take **3–4 months** on site; larger or double-storey projects run 4–6 months, plus design and approval time beforehand. ### Does an extension add value? A well-designed extension usually adds value, and a kitchen-diner or extra bedroom often returns much of its cost — though you can hit a local price ceiling in some areas. Build quality and design matter more than size. ### Do I need an architect? For anything structural you’ll need drawings and often a structural engineer. An architect isn’t legally required, but professional design usually pays for itself on larger or more complex extensions. ### Ready to start your project? Get matched with a trusted local pro — free and no obligation. ### Get a Free Quote! Start your project in under a minute. ### Keep reading Ready when you are ## Planning a project? Make it happen today! From fresh ideas to trusted installers, we’re here to get your home renovation project moving—quick, simple, and stress-free.