--- title: "How Much Does a House Extension Cost in 2026? | J&Co" description: "House extension cost guide for 2026 — single-storey, double-storey, wrap-around and side return prices per m². Honest figures from a Hertfordshire builder." lang: en-GB json-ld: | [ { "@context": "https://schema.org", "@type": "Article", "headline": "How Much Does a House Extension Cost in 2026?", "description": "House extension cost guide for 2026 — single-storey, double-storey, wrap-around and side return prices per m². Honest figures from a Hertfordshire builder.", "mainEntityOfPage": "https://jandco-contractorsltd.co.uk/guides/how-much-does-a-house-extension-cost/", "datePublished": "2026-05-07", "dateModified": "2026-05-07", "author": { "@type": "Person", "name": "Jamie Pocock", "jobTitle": "Owner & Lead Contractor", "worksFor": { "@id": "https://jandco-contractorsltd.co.uk/#business" } }, "publisher": { "@type": "Organization", "name": "J&Co Contractors", "url": "https://jandco-contractorsltd.co.uk" }, "image": [ "https://jandco-contractorsltd.co.uk/assets/upload-009-DFap0EVo.jpeg" ] }, { "@context": "https://schema.org", "@type": "FAQPage", "mainEntity": [ { "@type": "Question", "name": "How long does an extension take to build?", "acceptedAnswer": { "@type": "Answer", "text": "Single-storey rear: 14–18 weeks build. Side return: 12–16 weeks. Double-storey: 16–22 weeks. Wrap-around: 18–24 weeks. Add 12–20 weeks for design, planning and prep before site start. Full project from first call to handover: typically 8–14 months." } }, { "@type": "Question", "name": "Will an extension add more value than it costs?", "acceptedAnswer": { "@type": "Answer", "text": "Often yes in Hertfordshire and Essex. A well-designed kitchen extension typically adds £80,000–£150,000 to a £500,000–£700,000 family home — frequently 20–40% above its cost. Investment case is good, but only if the work is to the standard surveyors and buyers expect." } }, { "@type": "Question", "name": "Do I need an architect?", "acceptedAnswer": { "@type": "Answer", "text": "For anything more complex than a small rear extension, yes — strongly recommended. Good architects pay back their fees in better design, smoother planning approval and fewer site variations. We work with several trusted local architects and can introduce you." } }, { "@type": "Question", "name": "Can I project-manage it myself to save money?", "acceptedAnswer": { "@type": "Answer", "text": "Possible but rare to actually save money. Self-managed projects typically run 20–40% over budget and 30–60% over time because trade scheduling and snagging eat the savings. Owner-led main-contractor delivery (single point of accountability) is usually the cheaper long-run option for most homeowners." } }, { "@type": "Question", "name": "Can you handle planning and Building Control as part of the project?", "acceptedAnswer": { "@type": "Answer", "text": "Yes — we coordinate planning submissions and Building Control sign-off through East Herts Council, Uttlesford and the surrounding authorities. Single point of contact, single owner-led project management." } }, { "@type": "Question", "name": "Do you offer fixed-price extension quotes?", "acceptedAnswer": { "@type": "Answer", "text": "Yes — every quote is itemised line by line with a fixed price for the agreed scope. Variations are quoted in writing before action. The number you sign is the number you pay, barring genuinely unforeseen ground conditions found at dig." } } ] }, { "@context": "https://schema.org", "@type": "BreadcrumbList", "itemListElement": [ { "@type": "ListItem", "position": 1, "name": "Home", "item": "https://jandco-contractorsltd.co.uk/" }, { "@type": "ListItem", "position": 2, "name": "Building & Construction", "item": "https://jandco-contractorsltd.co.uk/building-construction/" }, { "@type": "ListItem", "position": 3, "name": "Extensions", "item": "https://jandco-contractorsltd.co.uk/building-extensions/" }, { "@type": "ListItem", "position": 4, "name": "How Much Does a House Extension Cost in 2026?", "item": "https://jandco-contractorsltd.co.uk/guides/how-much-does-a-house-extension-cost/" } ] } ] --- We use essential cookies to run this site, and optional cookies only with your consent. [Cookie policy](/cookie-policy/) AcceptReject Open 7 days · Hours vary by day · 25 years' experience [Office: 01279 216 215](tel:01279216215) | [Mobile: 07379 964569](tel:07379964569) [![J&Co Contractors logo](/assets/jandco-logo-DkXiFtbE.png)](/) Services Areas [About](/about/) [Our Work](/our-work/) [Blog](/blog/) [Reviews](/reviews/) [Contact](/contact/) [01279 216 215](tel:01279216215) [Free Quote](/contact/) 1. [Home](/) 2. [Building & Construction](/building-construction/) 3. [Extensions](/building-extensions/) 4. How Much Does a House Extension Cost in 2026? Guide · Extensions # How Much Does a House Extension Cost in 2026? Extensions in 2026 typically cost £2,200–£3,200 per m² for a standard build, with kitchen-extension fitouts pushing that higher. Here are the honest 2026 figures we quote on real Hertfordshire and Essex jobs. Last updated: May 2026 · By Jamie Pocock Quick Answer **UK extension costs in 2026: single-storey rear £45,000–£100,000, side return £55,000–£90,000, double-storey £80,000–£160,000, wrap-around £100,000–£200,000+.** Per m², expect £2,200–£3,200 for standard build, £3,200–£4,200 for high spec, and £4,200+ for luxury kitchens with bi-fold doors and premium finishes. Hertfordshire and Essex prices broadly track the national figures; London adds 25–40%. ![Recently completed single-storey rear extension on a Hertfordshire family home](/assets/upload-009-DFap0EVo.jpeg) ## Cost by extension type (2026) ### Single-storey rear extension (£45,000–£100,000) The most common extension type — open-plan kitchen-diner schemes added to the back of the house. Typical floor areas 15–35m². Standard build £2,200–£3,000/m²; with a fitted kitchen, bi-folds and premium flooring £3,000–£4,500/m² total. 14–18 weeks build time. ### Side return extension (£55,000–£90,000) Extension into the unused side passage of a Victorian or Edwardian terrace, typically widening a galley kitchen into a full kitchen-diner. Floor areas usually 8–15m² but the impact on layout is huge. Costs higher per m² because of party-wall complexity and structural openings. 12–16 weeks. ### Double-storey extension (£80,000–£160,000) Two-floor extension giving extra ground-floor living space plus an additional bedroom (often with en-suite) above. Typical floor areas 20–40m² per floor. Better cost per m² than single-storey because foundations and roof costs spread across two floors. 16–22 weeks. ### Wrap-around extension (£100,000–£200,000+) Combines side return and rear extension into a single L-shape. Typical floor areas 30–50m². Most space-creating option short of a full rebuild. Often combined with internal layout reconfiguration. 18–24 weeks. Full scope detail in our [extensions service page](/building-extensions/). ## What's normally included in those figures - Structural works (foundations, steel beams, openings, roof structure) - Brickwork to match existing (or rendered finish) - Roof — pitched tile or flat (EPDM/GRP), insulation to current Part L - Windows and external doors (standard UPVC or aluminium specs) - 1st and 2nd fix carpentry, electrics, plumbing, heating extension - Plastering ready for decoration (mist coat included) - Internal doors, skirting, architrave - Building Control submission, inspections and final sign-off - Written completion sign-off ## What's normally NOT included - Architect and structural engineer fees (typically £4,000–£10,000 separate) - Planning permission application fee (£258) and possible drawings revisions - Party Wall Act notices and surveyor (£1,200–£3,500 if required) - Kitchen cabinets, worktops and appliances (separate trade — £8,000–£40,000+) - Bathroom suites and tiling (typically £3,500–£12,000) - Floor finishes (engineered wood, tile, LVT) — typically £40–£120/m² - Final decoration (paint and wallpaper) - Bi-fold or sliding doors above standard spec (£3,500–£15,000+ uplift) - VAT (most domestic extensions are standard rate 20%) ## Cost per m² by spec level Spec level £/m² (2026) What you typically get Standard £2,200–£2,800 Brick or render, UPVC windows, pitched tile or flat EPDM roof, mid-spec internal finish. Mid-range £2,800–£3,500 Aluminium windows, lantern rooflight, underfloor heating, some bi-fold doors. High spec £3,500–£4,500 Premium aluminium glazing throughout, structural glass, designer kitchen package, full LED/smart-home wiring. Luxury £4,500+ Bespoke joinery, large-format porcelain flooring, premium worktops, whole-home integration with extension. Most Hertfordshire and Essex domestic extensions land in the standard-to-mid-range bracket. The single biggest cost variable is glazing — bi-fold and sliding doors at 4m+ widths can swing the project total by £15,000–£25,000. ## Costs people regularly forget **Architect and engineer.** Most builders quote the build, not the design. Architect £3,000–£7,000 typical residential. Structural engineer £1,000–£3,000 typical. Add up early — these are real costs paid before the build starts. **Planning vs PD.** Many single-storey rear extensions fall under Permitted Development. Larger extensions, double-storey work and conservation-area properties need full planning permission (£258 application fee, 8–12 week determination, possible drawings revisions). Confirm with your council before quoting. **Party Wall Act.** Any work within 6m of a neighbour's foundations or affecting a shared wall triggers Party Wall notices. Surveyor fees typically £1,200–£3,500 if your neighbour appoints their own. Build this into the timeline — notices need 2 months to expire. **Kitchen and bathroom packages.** Often the largest single cost outside the build itself. Mid-spec fitted kitchen £12,000–£25,000. Premium kitchen £25,000–£60,000+. Plan early — kitchen design influences services layout in the extension structure. **Living arrangements.** Single-storey rear extensions usually allow you to stay in residence; the kitchen is normally out for 4–6 weeks during fitout. Double-storey and wrap-around extensions are more disruptive — some clients move out for the final 4–6 weeks. **Overspend buffer.** Always carry a 10–15% contingency above the build quote. Variations always emerge — even on tight, well-managed projects. Build it into the budget rather than borrowing emergency funds at month 4. ![Recently completed roofing project by J&Co Contractors in Hertfordshire](/assets/wa-435-169-BMBPQKLs.jpeg) About the Author ## Jamie Pocock — Owner & Lead Contractor Jamie has 25 years' hands-on experience in roofing and building across Hertfordshire and Essex. He runs every J&Co Contractors project personally — from quote to completion — and writes these guides from real on-the-tools knowledge of what works, what doesn't, and what costs what in 2026. - 25 years' hands-on roofing and building experience - CRC Certified Roofer — self-certifies under Building Regs - SafeContractor approved - Written completion sign-off on every job FAQs ## Frequently asked questions ### How long does an extension take to build? ### Will an extension add more value than it costs? ### Do I need an architect? ### Can I project-manage it myself to save money? ### Can you handle planning and Building Control as part of the project? ### Do you offer fixed-price extension quotes? Related Guides [Single vs double-storey extensions](/guides/single-vs-double-storey-extensions/) [Loft conversion cost UK 2026](/guides/loft-conversion-cost-uk/) [Back to Extensions](/building-extensions/) ## Planning a 2026 extension? We deliver single, double-storey, side return and wrap-around extensions across Hertfordshire and Essex. Owner-led project management, single team, written fixed quote. [See our extensions service](/building-extensions/) [01279 216 215](tel:01279216215) Page last updated: May 2026 · J&Co Builders Ltd · 1 Ugley Hall Cottages, Bishop's Stortford CM22 6JB ![J&Co Contractors](/assets/jandco-logo-DkXiFtbE.png) Owner-led roofing and building contractors covering Bishop's Stortford, Hertfordshire and Essex. 25 years of hands-on trade experience. Open seven days. 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