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 - Building & Extensions Building & Extensions # House Extensions in Bishop's Stortford & Hertfordshire Single, double-storey, side return and wrap-around extensions managed end-to-end by an owner-led team — from foundations through to plastered, ready-to-decorate finish. Get a Free Quote 01279 216 215 25 years' experience Five-star rated Workmanship guarantee 25 Years' Experience Workmanship Guarantee SafeContractor Approved Gas Safe (where required) Open 7 Days Herts & Essex Coverage Overview ## Extensions Done Properly, From Foundations to Finish An extension is the largest building project most homeowners ever commission. The two things that decide whether it goes well — beyond design — are quality of trade and quality of project management. We provide both under one roof: groundworkers, brickies, carpenters, roofers, plasterers, electricians and plumbers all coordinated by Jamie personally. Most of our extension work falls into single-storey rear additions (kitchen-diner schemes), double-storey side and rear extensions (adding bedroom plus reception), wrap-around L-shaped extensions, and side returns on Victorian/Edwardian terraces. We handle planning coordination, Building Control, structural engineer input and full delivery — you have one number to call. Why It Matters ## Why Extension Projects Go Wrong The two consistent failure modes on residential extensions are poor sequencing of trades and open-ended pricing. Poor sequencing means you wait three weeks for a plasterer because nobody booked them in time. Open-ended pricing means a £55,000 quote becomes a £78,000 actual cost because every variation gets billed at day rates without prior approval. We address both directly. Trades are sequenced and locked in writing before we start. Materials are ordered to a programme. Variations are costed and approved before they happen. Cost certainty is the single most important thing we deliver — alongside the build itself. Our Process ## How We Deliver Building & Extensions 01 ### Initial Consultation Free site visit, brief discussion, early flag of any planning, structural or budget issues. No commitment. 02 ### Detailed Itemised Quote Fully written quote covering materials, labour, sub-contractors, skip hire, Building Control fees. Fixed price. 03 ### Programme & Scheduling Trades sequenced, materials ordered, weekly programme agreed in writing before we break ground. 04 ### Build & Updates Owner-led site management, daily clean-down, regular updates, all variations approved in writing before action. 05 ### Handover & Guarantee Final walk-round, snagging completed, completion sign-off on completion. Benefits ## What You Get with J&Co ### Fixed Written Quotes Every project itemised and fixed before we start — no creeping extras, no day-rate drift. ### All Trades In-House Groundworkers, brickies, roofers, plasterers, electricians coordinated by us, not subbed out and forgotten. ### Owner-Led Management Jamie runs every site personally — you speak to the decision-maker, not an account handler. ### Workmanship Guarantee Workmanship cover backed by insurance on every extension we deliver. Technical Detail ## Single-Storey, Double-Storey or Wrap-Around — What's Right? Single-storey rear extensions are the most common — typically extending the kitchen and creating a kitchen-diner-living space with bifold or sliding doors to the garden. Cost-effective per square metre, often achievable under permitted development rights, and the highest impact for most family homes. Double-storey extensions add a bedroom (and often an en-suite) above a reconfigured ground-floor space. Cost per square metre is significantly lower than single-storey because you're sharing foundations, roof and external walls between two floors. Almost always requires planning permission and a structural engineer involved from day one. Side returns on Victorian and Edwardian terraces are a specialism — filling in the awkward L-shape created by the original side passage to dramatically widen the kitchen. Common across Bishop's Stortford and Sawbridgeworth on period properties. Requires careful work where the new structure ties into existing walls. Wrap-around extensions combine a rear and side extension into one project. Big-impact, big-cost, and the most complex of the four. Worth doing when the kitchen needs full reconfiguring rather than just enlarging. For loft space adjustments at the same time see our loft conversion service. For full-house refurbishment scope see renovations and refurbishments. Two-storey rear extension delivered end-to-end by J&Co Contractors. Honest Pricing ## How Much Does a House Extension Cost in Hertfordshire? Honest 2026 ranges for our area. Every project quoted individually after a site visit and brief discussion of what you actually want. Single-storey rear £40,000–£90,000 Typical 4m × 5m rear extension including kitchen relocation, bifold doors and finishes. Double-storey rear £75,000–£140,000 Adds bedroom plus en-suite above reconfigured ground floor — better £/m² than single-storey. Wrap-around £100,000–£200,000+ Rear plus side return combined — highest impact, highest cost, fully bespoke quote. ### What affects the price - Footprint size (m²) - Single vs double storey - Glazing specification (bifold, slider, lantern) - Kitchen relocation and finish - Ground conditions and foundations - Planning vs permitted development route Get Your Free Written Quote Service Area ## Areas We Cover for Building & Extensions We deliver this service across our full Hertfordshire and Essex catchment. Regular projects in Bishop's Stortford, Sawbridgeworth, Harlow, Saffron Walden, Stansted Mountfitchet, Great Dunmow, Epping, Ware, Hoddesdon, Broxbourne, Cheshunt, Welwyn Garden City and Stevenage. Outside this list? Call us with your postcode — we frequently work the wider London fringe and across the rest of Hertfordshire. Guides ## Building & Extensions guides & cost advice Free, no-nonsense reading from Jamie on the questions we get asked most about building & 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. - Single vs Double-Storey Extensions: How to Choose Double-storey extensions cost more in absolute terms but cheaper per m² and add more value. Single-storey is faster, less disruptive, and often achievable under Permitted Development. Here's the honest comparison. Recent Work ## Recent Building & Extensions Projects View full portfolio FAQs ## Building & Extensions — Frequently Asked Questions ### svg]:rotate-180 text-left font-bold text-base hover:no-underline py-5" data-radix-collection-item=""> How long does a typical extension take to build? ### svg]:rotate-180 text-left font-bold text-base hover:no-underline py-5" data-radix-collection-item=""> Do I need planning permission for an extension? ### svg]:rotate-180 text-left font-bold text-base hover:no-underline py-5" data-radix-collection-item=""> Do you handle the architect and structural engineer? ### svg]:rotate-180 text-left font-bold text-base hover:no-underline py-5" data-radix-collection-item=""> Can I live in the house during the build? ### svg]:rotate-180 text-left font-bold text-base hover:no-underline py-5" data-radix-collection-item=""> What's included in your fixed quote? ### svg]:rotate-180 text-left font-bold text-base hover:no-underline py-5" data-radix-collection-item=""> What about variations or extras? ### svg]:rotate-180 text-left font-bold text-base hover:no-underline py-5" data-radix-collection-item=""> Is the work guaranteed? Related Services Loft Conversions Renovations & Refurbishments Brickwork & Masonry Flat Roofing Back to Building & Construction ## Get a Free Extension Quote Owner-led consultation, fixed itemised quote, fully managed build. Across Hertfordshire and Essex. Request Free Quote 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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