Most UK kitchen extensions in 2026 generally fall within a broad cost range reflecting size, specification and location variations. Size, specification and location move that figure more than anything else. Whatever your target, the sensible next step is the same: get three itemised quotes that separate the building shell from the kitchen fit-out, then add a contingency on top.
TL;DR:
- The cost of a 25m² mid-spec kitchen extension typically ranges from £45,000 to £65,000.
- Structural elements like steelwork and large doors can significantly increase costs regardless of size, especially in older or complex projects.
- Regional location impacts budget, with London costing 20% to 40% more than the national average, while the North West can be 10% to 15% cheaper.
- It’s crucial to request itemised, fixed-price quotes separating shell and fit-out costs, and to clarify who manages building control and party wall issues.
- Most delays and cost overruns stem from site issues like drainage, structural surveys, or scope of work overlooked before signing a contract.
Table of Contents
- How much does a kitchen extension cost by size?
- Shell versus fit-out: where does the money actually go?
- What does a kitchen extension cost in the North West versus London?
- What are the planning and Building Regulations fees for 2026?
- How do you get quotes you can actually compare?
- How long does a kitchen extension take, and what should you budget for delays?
- Why does hands-on project experience matter for cost control?
- What actually drives kitchen extension costs, and what gets overstated?
- How Complete Property Solutions can help
- Sources
How much does a kitchen extension cost by size?
Size sets the starting point for any budget, but specification decides where within that range you land.
- Small (around 15m²): roughly £27,000 to £38,000, midpoint about £30,000
- Medium (around 25m²): roughly £44,000 to £78,000, midpoint about £60,000
- Large (around 35m² to 40m²): roughly £70,000 to £110,000, midpoint around £90,000
Per m² guidance: costs are broadly categorized as budget, mid-spec, and high-end, with price per m² increasing accordingly.
Take a 25m² mid-spec project as a worked example. The shell (foundations, walls, roof, glazing, insulation) might come to £30,000, with the kitchen fit-out, including units, worktops and appliances, adding a further £25,000 to £30,000. That combination sits comfortably within the £35,000 to £75,000 range that industry guides quote for typical UK projects this year, and it lines up with RenovationCosts’ £42,000 to £78,000 estimate for full supplied-and-fitted schemes.
Shell versus fit-out: where does the money actually go?
Every kitchen extension splits into two distinct cost pools, and understanding that split helps you spot where to save and where not to skimp.
The shell covers everything that makes the room structurally sound and weatherproof: foundations, brick or block walls, roof structure and covering, glazing, insulation, drainage, and internal plastering. This typically absorbs 45% to 55% of the total budget.
The fit-out covers the kitchen itself: units, worktops, appliances, tiling, plus the electrics and plumbing needed to connect a sink, hob and appliances. This usually makes up the remaining 45% to 55%, and it’s the area where specification choices swing costs most dramatically.
Certain elements push a budget upward regardless of size:
- Structural steel (RSJs) for opening up load-bearing walls, particularly on side-return projects
- Large sliding or bi-folding doors, which carry higher unit and installation costs than standard glazing
- Poor site access, which increases labour time and material handling costs
- Extensive groundworks where ground conditions are unstable or drains need diverting
Side-return extensions on older terraced houses tend to run higher per m² because they often involve drain diversion, party-wall negotiations and steelwork to remove existing load-bearing walls. If you’re weighing up a side-return against a rear extension, our side extension cost guide breaks down that comparison in more detail.
Pro Tip: Ask your contractor to price the shell and fit-out as separate line items on the same quote. It makes comparing builders far easier, and it shows you exactly where you can trim spend without compromising the structure.
What does a kitchen extension cost in the North West versus London?
Location alone can shift your budget by a third or more. London and the South East typically carry a 20% to 40% premium over the national average, driven by labour rates, site access restrictions and higher material delivery costs. The North West, by contrast, tends to run 10% to 15% below the national average, which makes areas like Warrington, St Helens, Great Sankey and Culcheth genuinely good value for like-for-like specification.
Rough example budgets for a mid-spec build:
- 15m² extension: costs vary regionally, with London generally priced higher than many other areas
- 25m² extension: costs depend significantly on location, with London at the higher end
- 40m² extension: location and specification greatly influence final budget, with London projects tending to be more expensive.
Local factors still matter within the region. Conservation areas around parts of Wigan and Ormskirk, party wall agreements for terraced or semi-detached properties in Rainhill or Lowton, and restricted site access on older streets in Penketh or Haydock can all add cost regardless of the regional discount.
What are the planning and Building Regulations fees for 2026?
Most single-storey rear kitchen extensions fall under permitted development and don’t need full planning permission, provided they meet height, depth and boundary rules. Where they don’t, householder planning applications are subject to the government’s 2026 fee indexation, which sets specific fee brackets for household development categories.
Building Regulations approval is separate from planning and applies regardless of whether planning permission is needed. The Building Regulations 2010 require approval for structural work, new drainage, electrics, and replacement windows or roofing, among other elements.
| Project type | Typical building-control charge |
|---|---|
| Single-storey extension (under 40m²) | generally ranges from low to moderate fees |
| Single-storey extension (40m² to 40m²) | fees are moderate and vary by council |
| Two-storey extension | fees are higher, depending on complexity |
Local authorities publish their own standard building-control fee schedules, so figures vary slightly by council.
- Standard-rated builders’ work is subject to 20% VAT
- Some renovation and conversion work may qualify for reduced VAT rates in specific circumstances, so check with your contractor and HMRC guidance before assuming a rate
How do you get quotes you can actually compare?
Two quotes that look similar on price can hide wildly different scopes of work. A proper comparison depends on asking the right questions upfront.
- Request an itemised, fixed-price quote with shell and fit-out costs shown separately.
- Ask who manages the Building Control submission and whether that’s included in the price.
- Ask whether party wall matters, RSJ supply and installation, and scaffolding are covered or excluded.
- Get a clear timescale with start and completion dates, plus a payment schedule tied to project milestones.
- Confirm the contractor holds public liability insurance and can provide references or completed project examples.
Watch for red flags: vague exclusion lists, unusually low deposits, or reluctance to provide proof of insurance. Itemised quotes that separate professional fees, building control charges and construction costs make negotiation far simpler later on.
Pro Tip: If a quote seems significantly cheaper than the others, ask exactly what’s excluded before you get excited. It’s almost always the fit-out finish, structural contingency, or Building Control fees hiding in the small print.
How long does a kitchen extension take, and what should you budget for delays?
A small kitchen extension typically takes several weeks on site, with medium projects requiring longer and larger or structurally complex builds taking even more time, especially if planning permission or agreements add delays.
Living through a build is easier with a temporary kitchen setup and phased works, so you retain some cooking facilities throughout. Most guides recommend holding at least a 10% contingency against your total budget, and we’d suggest 10% to 15% for older properties, where unexpected groundwork or drainage issues are more common once walls come down.
Why does hands-on project experience matter for cost control?
We have managed design-and-build projects across the North West for many years, and that experience shapes how we quote. As members of the Guild of Master Craftsmen, we provide transparent, fixed-price quotations rather than estimates that shift once work begins.
Engaging a contractor early, before final designs are locked in, lets structural surveys and RSJ requirements get identified before pricing rather than after. That single step removes most of the guesswork that causes budgets to creep once a project is underway, as explained in detail in our Building & Renovating in Mallorca — What Buyers Need to Know About Costs, Trades and the Law partner guide. We work across Warrington, St Helens, Wigan, Great Sankey, Penketh, Culcheth, Lowton, Rainhill and Haydock, and the regional pricing patterns above reflect what we see on real projects in these areas.
What actually drives kitchen extension costs, and what gets overstated?
Most advice on this topic obsesses over headline per m² figures, and that’s the wrong place to start. The bigger risk sits in what doesn’t get priced at all: the structural survey nobody commissioned before the quote, the drain run nobody checked, the party wall conversation left until after the deposit’s paid.
Conventional guidance tells homeowners to compare quotes on total price. That’s backwards. Two quotes at £58,000 can represent completely different levels of risk if one contractor has actually surveyed the site and the other is pricing from a floor plan and a guess. The number that matters more than the total is what’s excluded, because that’s where the real cost creep happens three weeks into the build.
If there’s one thing worth prioritising above spec choices and glazing upgrades, it’s this: pick a contractor who investigates structural issues, drainage and Building Control requirements before they write your fixed price, not after. Everything else, the tiles, the worktop, the bi-fold doors, is negotiable later. The groundwork underneath your quote isn’t.
— Gareth
How Complete Property Solutions can help
If you’re weighing up quotes and want a design-and-build team that prices honestly from the outset, that’s precisely what we do. Complete-Property-Solutions is the practical alternative to piecing a project together yourself across separate architects, structural engineers and trades. We manage your kitchen extension from initial survey through to final finish, under one fixed-price contract.
Get in touch to arrange a survey and see what a kitchen extension would genuinely cost for your home, using our house extensions service.
This article is general information, not a substitute for advice from a qualified financial advisor. Consult a qualified financial professional about your own circumstances before acting on anything here.
Sources
- Gov
- Planning fees – annual indexation from 1 April 2026
- Building control fees — sample local authority schedule (Hart)
- Kitchen extension cost UK 2026 — BestBuilders
