Kitchen Extensions
Open-plan kitchen-diners that transform how your family uses your home. Designed around your lifestyle, built to last.
The Heart of Your Home, Reimagined
The kitchen extension has become the single most requested building project in the UK, and for good reason. A cramped, separate kitchen tucked away at the back of the house doesn't match how modern families actually live. You want to cook while the kids do homework. You want to host without being cut off from your guests. You want light, space, and a direct connection to the garden.
A well-designed kitchen extension delivers all of this. By extending into the rear or side of your property and opening up the internal walls, you create one flowing space that serves as kitchen, dining room, and living area. Add bi-fold doors or large sliding doors to the garden, and you've effectively doubled your ground floor for half the year.
We build kitchen extensions across the UK — from side-return conversions on Victorian terraces in London to large rear extensions on family homes in Manchester, Birmingham, and Bristol. The build itself follows the same principles as any house extension, but the kitchen-specific elements — utility connections, ventilation, floor finishes, and layout — need careful planning from day one.
Kitchen Extension or Separate Kitchen Refit?
If your kitchen is a decent size but just needs updating, a refit (new cabinets, worktops, appliances) might be enough. A full kitchen refit costs £8,000–£25,000 and takes 2–3 weeks. No building work, no planning, minimal disruption.
But if your kitchen is genuinely too small — if you can't fit a dining table, if two people can't work side by side, if there's no natural light — then extending is the answer. The building work costs more, but you're creating an entirely new room that changes how your whole ground floor functions.
The sweet spot for value is combining the extension build with a new kitchen fit-out. You're already ripping out the old kitchen to knock through the wall, so you're not wasting money on a kitchen you'll be throwing away. Design the new kitchen for the new space from the start — including appliance positions, socket locations, extraction routes, and plumbing runs. This avoids costly changes mid-build.
Most of our clients spend roughly 50–60% of their total budget on the building work and 40–50% on the kitchen itself, although that ratio shifts significantly with high-end kitchen brands.
Types of Kitchen Extension
The best layout depends on your property, your plot, and what you want to achieve. These are the configurations we build most often.
Rear Kitchen Extension
The classic approach: extend straight out from the back of the house. A 4m depth gives you enough room for a generous kitchen plus dining area. Go to 5–6m and you can add a sofa area or snug. The rear wall is typically replaced with large glazing — bi-fold doors, sliding doors, or a combination of fixed and opening panels. This is the most straightforward type to build and usually the best value. Under permitted development, you can go 6m (semi) or 8m (detached) without planning permission.
Side-Return Kitchen Extension
If you live in a Victorian or Edwardian terrace with a narrow side alley beside the kitchen, a side-return extension absorbs this wasted space — typically adding 1–2 metres of width. This alone can transform a narrow galley kitchen into a proper room. Most side-returns are combined with at least 2–3 metres of rear extension to create enough depth for a dining area. The structural work involves removing the existing side wall and supporting the first floor above with steel beams. Popular in London boroughs where every square metre counts.
Wrap-Around Kitchen Extension
Combines a rear extension with a side extension in an L-shape, giving you the maximum ground floor area. Works particularly well on end-of-terrace and semi-detached properties with side access. The extra width lets you fit an island with seating on three sides and still have room for a dining table. These projects usually need planning permission because of the side element. Build time is 12–18 weeks. Budget £45,000–£80,000 for the building work before kitchen costs.
Kitchen-Diner Knock-Through
Not strictly an extension — this involves removing the wall between an existing kitchen and dining room to create one open-plan space. If the wall is load-bearing (most internal walls parallel to the front of the house are), a steel beam (RSJ) is installed to support the structure above. This is a fraction of the cost of an extension (£3,000–£8,000 including the steel and making good) and can be completed in 1–2 weeks. Worth considering if your combined kitchen and dining room are already a decent size when opened up.
Orangery / Garden Room Kitchen
A glazed structure with a solid roof perimeter and a central glass lantern. Sits between a traditional brick extension and a conservatory. The solid roof section provides space for downlighters and gives a more "room-like" feel than a full glass roof. Popular for kitchen-diners because the combination of solid and glass roof reduces overheating in summer while still flooding the space with light. More expensive than a standard brick extension per square metre — budget £2,500–£3,500/m² — but the visual impact is significant.
Open-Plan Rear with Roof Lantern
A flat-roofed rear extension with one or more roof lanterns (raised glass panels in the roof) to bring light deep into the room. This solves the main problem with deeper extensions — the further you extend from the house, the darker the middle of the room becomes. A 1m × 2m roof lantern costs £2,000–£4,000 installed and makes a dramatic difference. Specify electric-opening vents in at least one lantern for ventilation — kitchens generate a lot of heat and moisture.
Kitchen Extension Costs in 2026
We separate costs into two elements: the building work (shell, structure, services) and the kitchen fit-out (cabinets, worktops, appliances). This gives you a clearer picture of where your money goes.
Building Work — Shell & Structure
£1,500 – £2,500/m²
Covers everything from foundations to plastered walls: groundwork, blockwork, roof structure (flat or pitched), insulation, windows/doors, internal walls, electrics first and second fix, plumbing runs, plastering, and floor screed. A 20m² extension at mid-range spec costs £30,000–£50,000. Bi-fold doors add £3,000–£6,000 for a 3–4m opening.
Kitchen Fit-Out
£8,000 – £30,000+
This is where the range gets wide. Budget kitchens (IKEA, Howdens, Wickes) with laminate worktops come in at £5,000–£10,000 for units and installation. Mid-range (shaker-style, quartz worktops, integrated appliances) runs £12,000–£20,000. High-end bespoke kitchens from specialist manufacturers start at £25,000 and can exceed £50,000. Appliances are additional — budget £2,000–£5,000 for a decent set.
Underfloor Heating
£1,500 – £3,500
Highly recommended for kitchen extensions, especially with tiled or stone floors. Electric mat systems cost less upfront (£40–£60/m²) but more to run. Wet (water-based) systems cost more to install (£60–£90/m²) but are cheaper to operate, especially with a heat pump. We install the system before the floor screed is poured — it needs to be planned from the foundation stage.
Total Project Costs
£40,000 – £80,000
A typical complete project — 20–25m² extension with bi-fold doors, mid-range kitchen, quartz worktops, integrated appliances, underfloor heating, and full decoration — comes in between £40,000–£80,000 depending on location and specification. In London, add 20–30%. In the North, you can often achieve the same result for 15–20% less.
Planning Permission & Kitchen Layout
Planning Permission
Most single-storey kitchen extensions fall under permitted development, following the same rules as any house extension: up to 6m rear for semi-detached, 8m for detached, maximum eaves height 3m, materials to match.
The Prior Approval process (also known as the "larger home extension scheme" or "neighbour consultation scheme") allows even larger extensions without full planning permission. You apply to the council, who notify your neighbours. If no objections are raised within 42 days, you can proceed. This covers single-storey rear extensions up to 6m (semi/terraced) or 8m (detached) — the same as standard PD limits, but the process gives neighbours a formal say.
You'll need full planning permission if your extension is to the side and exceeds the PD limits, if you're in a conservation area, or if Article 4 directions apply to your property.
Building regulations apply to every kitchen extension. Key areas: Part L (insulation — new walls need a U-value of 0.18 W/m²K), Part F (ventilation — kitchens need either an openable window plus extract fan at 60 litres/second, or continuous mechanical ventilation), Part P (electrical work must be signed off by a Part P electrician or building control), and Part H (drainage if you're moving or adding soil/waste connections).
Getting the Kitchen Layout Right
Your kitchen designer and your builder need to talk to each other early. We've seen too many projects where the kitchen is designed after the extension is built, and the socket positions, plumbing runs, or extraction routes don't line up. Get the kitchen layout finalised before first fix starts — ideally before you submit the building regs application.
The working triangle: The relationship between your hob, sink, and fridge should form a rough triangle with each side between 1.2m and 2.7m. This isn't a rigid rule, but it keeps the most-used elements within easy reach of each other.
Island kitchens: You need at least 1m of clear space on all sides of an island — 1.2m is more comfortable, especially if you have drawers or an oven in the island. This means you need a room width of at least 4m to fit a 600mm-deep island with walkways either side. Many standard rear extensions are 3m wide, which is too narrow for an island — consider a wider or wrap-around extension if an island is non-negotiable.
Extraction: If your hob is on an island, you'll need either a ceiling-mounted extractor (noisy, visible) or a downdraft extractor built into the worktop (expensive, £800–£2,000). Wall-mounted extractors on a back wall are simpler and more effective. Plan the extraction route to the outside early — it dictates where the hob can go.
Lighting: Plan multiple circuits: task lighting over worktops, ambient lighting for the dining area, accent lighting for the island. Dimmer switches everywhere. The single biggest complaint we hear about finished kitchens is "not enough light" — you can never have too many downlights in a kitchen.
How Long Does a Kitchen Extension Take?
From first meeting to cooking Christmas dinner in your new kitchen — here's a realistic timeline.
Design & Approvals
6–10 weeks. Architectural drawings, structural engineering, building regs application. Simultaneously, begin your kitchen design — visit showrooms, finalise layout, choose appliances. If planning permission is needed, add 8 weeks.
Build Phase
10–14 weeks. Foundations (1–2 weeks), walls and roof (3–4 weeks), weathertight (windows/doors), first fix electrics and plumbing to kitchen design spec, underfloor heating if applicable, plastering, floor screed. Your existing kitchen stays usable until the knock-through.
Kitchen Fit & Finish
2–4 weeks. Knock-through, flooring laid, kitchen units installed, worktops templated and fitted (1–2 week lead time for stone), splashbacks, final electrics and plumbing connections, appliances fitted, decoration, snagging.
Things Your Builder Should Tell You
Before You Start
Order your kitchen early. Bespoke and mid-range kitchens have lead times of 4–8 weeks. Stone worktops are templated after the units are installed and take another 1–2 weeks to fabricate and fit. If you leave the kitchen selection until the build is underway, you'll add weeks to the project.
Think about where you'll cook. Set up a temporary kitchen in your dining room or living room with a microwave, kettle, portable induction hob, and a washing-up bowl. It's basic but functional. You'll need it for 2–4 weeks during the worst of the disruption.
Flooring goes in before the kitchen. Tiled or stone floors should be laid wall-to-wall before the units go in. This looks better, makes future kitchen replacements easier, and avoids issues with under-unit humidity. Engineered wood or LVT can go either way — discuss with your fitter.
Don't forget external works. The extension will probably sit on part of your patio or garden. Budget for re-landscaping, a new patio, drainage adjustments, and any fence or wall modifications. External works often add £3,000–£8,000 to the project that people forget to budget for.
Specification Decisions That Matter
Flat roof vs pitched: Flat roofs are standard on most kitchen extensions. Modern flat roofs use a warm-deck system with EPDM or fibreglass (GRP) membrane — both last 25+ years. A pitched roof costs more but can match the existing house better and creates a vaulted ceiling inside (stunning with exposed rafters).
Floor level: Your extension floor will be at a different level to your garden. Building regs require a minimum 150mm step down from the internal floor to the external ground level (to prevent water ingress). If you want a flush threshold for bi-fold doors, you'll need a drainage channel and careful detailing — it's achievable but costs extra.
Heating: Radiators or underfloor heating? Underfloor heating frees up wall space and is more comfortable underfoot, but it responds slowly — you can't quickly warm the room by cranking it up. A combination of UFH and a couple of radiators gives you the best of both. If you're extending a conventional boiler system, check your boiler has enough capacity for the extra radiators or UFH manifold.
Worktop materials: Quartz (£300–£500/m² installed) is the most popular choice — durable, non-porous, consistent colour. Granite is similar in price but each slab is unique. Dekton and Neolith (sintered stone) are the premium options at £400–£700/m² — they resist heat, scratches, and UV fading. Laminate (£100–£200/m²) is perfectly fine for a budget kitchen and today's laminates look far better than they used to.
Complementary Projects
House Extensions
For general information about extensions, structural work, and the building process, see our comprehensive house extensions guide.
Loft Conversions
The classic "extend up and out" — a kitchen extension below and a new bedroom above. We coordinate both projects to run efficiently.
Bathroom Renovations
Remodelling the ground floor often means moving or upgrading the downstairs WC. A good time to modernise the cloakroom as part of the project.
New Builds
If you're building from scratch, we design and build kitchens as part of the complete new build package. Bespoke layouts designed from the ground up.
Kitchen Extension Questions
The most common questions we get about kitchen extensions. Need more detail? Give us a call.
Common Questions
Details regarding our process, planning constraints, and project timelines.
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