We use essential cookies to run this site, and optional cookies only with your consent. Cookie policy AcceptReject Open 7 days · Hours vary by day · 25 years' experience Office: 01279 216 215 | Mobile: 07932 442502 Services Areas About Our Work Blog Reviews Contact 01279 216 215 Free Quote - Home - Building & Construction - Extensions - 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%. ## 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. ## 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–£2,800Brick or render, UPVC windows, pitched tile or flat EPDM roof, mid-spec internal finish. Mid-range£2,800–£3,500Aluminium windows, lantern rooflight, underfloor heating, some bi-fold doors. High spec£3,500–£4,500Premium 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. 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 ### svg]:rotate-180 text-left font-bold text-base hover:no-underline py-5" data-radix-collection-item=""> How long does an extension take to build? ### svg]:rotate-180 text-left font-bold text-base hover:no-underline py-5" data-radix-collection-item=""> Will an extension add more value than it costs? ### svg]:rotate-180 text-left font-bold text-base hover:no-underline py-5" data-radix-collection-item=""> Do I need an architect? ### svg]:rotate-180 text-left font-bold text-base hover:no-underline py-5" data-radix-collection-item=""> Can I project-manage it myself to save money? ### svg]:rotate-180 text-left font-bold text-base hover:no-underline py-5" data-radix-collection-item=""> Can you handle planning and Building Control as part of the project? ### svg]:rotate-180 text-left font-bold text-base hover:no-underline py-5" data-radix-collection-item=""> Do you offer fixed-price extension quotes? Related Guides Single vs double-storey extensions Loft conversion cost UK 2026 Back to 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 01279 216 215 Page last updated: May 2026 · J&Co Builders Ltd · 1 Ugley Hall Cottages, Bishop's Stortford CM22 6JB Owner-led roofing and building contractors covering Bishop's Stortford, Hertfordshire and Essex. 25 years of hands-on trade experience. Open seven days. 01279 216 215 (office) 07932 442502 (mobile) info@jandco-contractorsltd.co.uk 1 Ugley Hall Cottages, Bishop's Stortford CM22 6JB Open 7 days a week - Sun 07:00–17:30 - Mon 07:00–17:00 - Tue 07:30–17:00 - Wed 07:00–17:30 - Thu 07:00–17:30 - Fri 06:00–18:00 - Sat 09:00–17:00 We accept VISAAMEX PayG Pay ### Roofing - All roofing services - Flat Roofing - Roof Repairs & Maintenance - Emergency Roof Repairs - Guttering, Fascias & Soffits - Chimney Repairs & Repointing ### Building & Construction - All building services - Building & Extensions - Loft Conversions - Renovations & Refurbishments - Brickwork & Masonry - Damp Proofing & Waterproofing - Plastering & Rendering - Patio & Driveway Installations - Fencing & Garden Walls - Property Maintenance ### Areas We Cover - Bishop's Stortford - Stansted Mountfitchet - Sawbridgeworth - Great Dunmow - Harlow - Saffron Walden - Epping - Ware - Hoddesdon - Broxbourne - Cheshunt - Welwyn Garden City - Stevenage ### Company - About J&Co - Our Recent Work - Blog - Customer Reviews - Contact Us © 2026 J&Co Builders Ltd · Trading as J&Co Contractors · All rights reserved. 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