How Much Does a Kitchen Extension Cost?

A kitchen extension cost with Excellence Living starts from £20,000 for a kitchen reconfiguration within your existing footprint, £60,000 for a kitchen extension, and £45,000 for a garage-to-kitchen conversion. These are honest starting points rather than quotes, since the real figure for your home depends on the size of the opening, the ground it sits on, the steelwork involved and the glazing specified, all measured and priced properly at our free feasibility visit.

Most kitchen extension cost uk guides quote a single national average and leave it there, which tells you almost nothing about what your own project will cost. Extension costs are driven by structure, not a postcode figure, so this guide sets out honestly what moves the price at each starting point above, what a fully specified quote should itemise, and the costs people forget until they are already on site. The same seven factors decide what you actually pay, whatever kitchen extension route you are pricing, and location plays a real part in that too, since material and labour costs both vary from one part of the country to another.

What the three starting prices actually buy

Each of our three starting figures covers a genuinely different scope of structural work, and confusing them is the single most common reason a homeowner’s budget and expectations end up in different places before the first brick moves. Understanding which extension type you are actually pricing is the first step to knowing what to expect to pay.

£20,000 covers a kitchen reconfiguration within your existing footprint. This means opening the kitchen into an adjoining room, most often a dining room or lounge, with a structural steel beam carrying the load of the wall that used to be there. No new foundations, no new roof and no extension to the footprint of the house, which is why it sits at the lower end of the range. It suits households whose real problem is a closed-off layout rather than a genuine shortage of space. Our open-plan kitchen extension guide covers what this involves in more depth.

£60,000 covers a kitchen extension, the project we build most often and the figure most homeowners searching for kitchen extension cost are actually working towards. This is genuinely new structure, new foundations, new external walls, a new roof and glazing, built out into the garden or into a side-return extension. It buys real additional space rather than a reconfiguration of what already exists. Our kitchen extensions service page sets out the fuller range of extension types we build.

£45,000 covers a garage-to-kitchen conversion, converting an existing integral or attached garage into kitchen space, or into the connecting dining and family area beside a smaller extended kitchen. It sits between the other two figures because the walls, roof and foundations of the garage already exist, which removes a substantial chunk of the cost a full extension carries, whilst still needing structural openings, insulation upgrades and new services. It works particularly well where the garage sits directly beside the existing kitchen. See our garage conversions page for the wider detail.

None of these three figures is a quote, and no company that has not measured your actual walls, ground and drainage runs can honestly give you one. Try our kitchen cost calculator for an indicative range based on your own answers; your actual cost still depends on your property’s structure, access and final specification. What turns a starting point into a real number is the free feasibility visit, where everything above is measured, checked and priced for your specific property.

Average kitchen extension costs by project type

Average kitchen extension costs across our three project types sit at £20,000 for a reconfiguration, £45,000 for a garage-to-kitchen conversion and £60,000 for a full extension. Where a project sits within that range depends on the extension type, the size of the opening and the specification chosen, which is what the feasibility visit prices properly rather than estimating from a brochure. Whichever of the three you are pricing, extension costs are set by structure and specification, not by which starting point you begin from.

What Moves Your Kitchen Extension Costs Up or Down

Seven things move extension costs within and beyond the ranges above, and understanding them before your feasibility visit means going into that conversation with a realistic budget rather than a guess. A rear extension cost is not one number, it is the sum of everything below, and the same seven factors apply whether you are pricing a straightforward rear extension, a return extension or a wraparound.

Size. The larger the new or altered space, the more foundations, walling, roofing and glazing are needed, and cost scales with it fairly directly. A modest three metre extension across the back of a terraced kitchen costs meaningfully less than the same extension run the full width of a detached house.

Ground conditions and foundations. What is under your garden has a real effect on cost. Clay soil that shrinks and swells with the seasons, a sloping site, made-up ground from a previous build, or nearby tree roots can all mean deeper or more specialised foundations than a straightforward trench fill. This is decided on site, not from a desk, and it is one reason two similar-looking extensions on similar streets can carry different costs.

Steelwork and how much wall you remove. The size of the opening you are creating, and therefore the span and depth of the structural steel beam needed to carry the load above it, is one of the most safety-critical and cost-relevant decisions in any kitchen project. A single beam over a modest opening is a different calculation to the steelwork needed to open an entire rear wall onto a wide-span extension. An engineer calculates the exact specification, and the finished work is inspected before it is covered over.

Glazing and roof lights. Bifold doors or sliding doors across the full width of a new extension, roof lights bringing daylight into the depth of the room, or a glazed link connecting old and new all add meaningfully to the cost compared with a smaller, more conventional arrangement. This is also where a kitchen extension earns its keep day to day, since light and a connection to the garden are usually what a household notices first.

Drainage moves. Where the new layout moves the position of a sink or repositions existing drainage runs, below-ground drainage work is added to the project. Moving drainage further from existing runs, or working around a manhole within the new footprint, adds real cost, and it is exactly the kind of detail a one-line estimate glosses over.

Kitchen spec. The specification you choose for the finished kitchen, as a budget line rather than a product list, moves the overall project cost. We do not fit kitchen units, worktops or appliances, that is a separate decision for you to make, but the space we hand over is built to accommodate whichever specification you choose. A custom specification, a non-standard glazing configuration or a bespoke structural finish can add significant cost compared with a standard one, and even a routine change, like moving a drainage run further than the drawings first suggested, can carry its own significant cost, which is worth flagging at the feasibility visit so the structural work is designed around it from the outset.

Finishes. Plastering, flooring, decoration and the general finish specification all sit on a range, and a higher specification finish costs more than a standard one. Interior finishing touches beyond a basic decoration allowance, upgraded skirting, feature lighting, underfloor heating or a higher specification floor covering, can typically add a further £1,000 to £5,000 depending on how far above standard you choose to go. This is the part of the budget you have the most discretion over, worth deciding deliberately rather than letting it be decided by whatever is left once the structural budget is spent.

Single storey extension cost versus double storey extension cost

A single storey extension cost and a double storey extension cost are not simply a multiple of each other. Adding an upper floor means foundations sized for the extra load, additional structural steel, and a second run of walls, insulation and glazing above the ground floor, so the finished project typically costs meaningfully more than the equivalent single storey extension, not roughly double, since extension costs scale with structure rather than simply the number of storeys involved. Most of our kitchen projects are single storey, and the £60,000 starting figure above reflects that. Where a household needs a bedroom or bathroom as well as extra kitchen space, building both storeys together at once can still work out more cost-effective than adding an upper floor as a separate project later, since the foundations only need digging once.

Flat roof and material costs

A flat roof extension, often specified with roof lights set into it, is generally less expensive than a pitched roof of the same footprint, since it uses less material and a simpler structure. Material costs also move with the glazing package chosen, bifold doors and full-height glazing carry a higher material cost than a smaller window, worth deciding early since it shapes how you will use the room. Larger glazing packages, bi fold doors across the full rear elevation or a glazed roof lantern, are priced properly at the feasibility visit alongside everything structural, since these material costs are one more line inside your overall extension costs.

Is your ground condition or a nearby tree likely to change your foundation cost? It is impossible to say without a site visit, and guessing either way risks over or under-budgeting. Our free feasibility visit checks ground conditions on your actual plot before any figure is finalised.

Planning Permission and Building Control

Before a single foundation is dug, two separate questions need answering honestly: do you need planning permission, and what does building control expect to see. They are not the same process, and conflating them is one of the more common ways a kitchen extension project loses time before it has properly started.

A standard single storey extension, built as a rear extension rather than to the side, often falls under permitted development rights, provided it stays within the size and height limits your local authority sets, and does not sit on a property where those rights have been removed by an Article 4 direction or a planning condition. Where a project does need planning permission, whether because of scale, a conservation area or a listed building, we check this honestly at the feasibility visit before you spend anything on drawings, so you know from day one whether you need planning permission or not.

Building control is a separate, unavoidable process that applies regardless of the planning position. Structural engineer drawings, prepared to cover the steel beam and foundation design, are submitted as part of that building regulations approval process, and structural engineering fees for that work should always appear as their own line on a fully specified quote rather than being folded into a general allowance. A structural engineer also confirms what is happening below ground, since existing services, drainage runs and underfloor heating pipework already in place all affect how the new foundations and floor build-up are designed around them.

Getting this sequence right, planning position first, then a structural engineer and the statutory sign-off that follows, is how a kitchen extension project keeps extension costs predictable from the first day on site, rather than a wall being opened before the paperwork behind it is settled.

Cost per square metre and why it is a blunt instrument

Extension costs worked out per unit of floor area are a figure people reach for because they look like a clean way to compare projects, and it is worth understanding both what that figure can tell you and where it quietly misleads.

Take our £60,000 starting figure for a kitchen extension across a typical 20 square metre addition, and the working-out lands around £3,000 per square metre. That number is a reasonable sanity check against other quotes, and if a competing quote comes in dramatically below it, it is worth asking what has been left out rather than assuming you have found a bargain.

Where this metric becomes a blunt instrument is everything it hides. Two extensions of an identical size can carry genuinely different costs once ground conditions, steelwork, glazing specification and drainage moves are accounted for, yet a bare figure presents them as the same project. A rear extension with a full-width run of bifold doors and two roof lights will cost more than the same size extension with a single window. Location significantly influences the cost of kitchen extensions in the UK too, since material costs and the cost of labour both differ by region. A project of identical scope on detached houses in the south east will often carry a different figure to the same project in the north west, or to the same project again across Bristol, North Somerset and Somerset, which is why we price from a local site visit rather than a national table.

The same blunt-instrument problem applies to a garage-to-kitchen conversion, since much of the cost saving comes from walls, roof and foundations that already exist rather than from the space itself. Use this figure as a rough sanity check if you find it useful, never as the number you budget against. The only number worth budgeting against is a fully specified price for your actual project, which is exactly what the free feasibility visit produces.

What a fully specified quote should itemise

A one-line figure on a piece of paper is not a quote, it is a guess with a total at the bottom, and it is one of the most common reasons a kitchen extension cost creeps well beyond what a homeowner budgeted for. A fully specified quote should set out each element of the project separately, so you can see all the costs and understand why extension costs land where they do, rather than a single total with nothing behind it.

Groundworks and foundations should be itemised on their own, reflecting the ground conditions actually found on your plot. Structural steel should be itemised separately, covering the engineer’s calculations, the beam itself and the labour to install it, since this is where an underspecified quote is most dangerous to discover once the walls are open. The building envelope should be its own line, distinct from the glazing package, which should state exactly which doors, windows and roof lights are included.

Drainage should be itemised wherever the new layout moves existing runs, along with electrics, heating and ventilation. Upgrading plumbing or electrics beyond the footprint of the new kitchen, moving a boiler or bringing in a new circuit, for example, is priced against the scope of works rather than assumed, and a fully specified quote should show that as its own line rather than folding it into a general allowance. Decoration and finishes should be their own line, and statutory fees for Building Regulations should be named, not buried inside a general allowance, and the same goes for an engineer’s fee.

A fully specified quote should also state plainly what is not included, since gaps cause more disputes than the figures that are in it. We define the scope of works in writing at the feasibility visit, which is the single biggest reason our projects do not creep once work is underway, and it is how the total cost stays predictable from your first visit through to your completion certificate.

The costs people forget

Beyond the headline structural figure, there is a shorter list of hidden extension costs that genuinely catch households out, mostly because they sit outside what most people think of as “the build” and never make it into the mental budget.

Statutory fees are a routine cost of any structural project, covering the inspections that confirm your extension meets current regulations and the completion certificate at the end of it. They are not optional, whatever a subcontracted builder working without proper sign-off might suggest, and skipping them stores up a bigger cost for whoever sells the house later.

A party wall agreement applies wherever your extension sits near or on a boundary shared with a neighbour. This is common on terraced and semi-detached properties, including many semi detached houses across Bristol and the wider South West. Serving notice and reaching that agreement is routine rather than a red flag, but the surveyor’s fee that can accompany it is worth budgeting for rather than discovering partway through.

An engineer’s fee covers the calculations behind your steel beam and foundation design, sometimes quoted separately. Waste removal and skips add up over a ten to sixteen week build and are easy to underestimate, and they sit alongside labour costs and other extension costs most households do not think to budget for.

Building work of this scale disrupts daily life for weeks at a time, which is exactly why a temporary kitchen, a kettle, a microwave and somewhere to wash up, is a real cost for most of the build, since your existing kitchen will usually be out of action whilst the wall it depends on is removed. Decoration beyond the extension itself, an adjoining hallway disturbed by the works, is another line people forget until the plaster dust has settled.

None of these should come as a surprise on a properly run project. We talk through every one honestly at the feasibility visit, and they are itemised in your fully specified price rather than left for you to discover as the build progresses.

Budgeting and contingency

Sensible budgeting for extension costs includes a contingency of 10 to 20 per cent on top of your fully specified price. On a £60,000 extension, that means setting aside a further £6,000 to £12,000, and it is one of the simplest ways to save money in the long run, since an unplanned bill mid-build is always more disruptive than the same amount set aside in advance. That advice is aimed at the industry norm rather than at us. A contingency exists because most quotes are not fully specified before work starts, and the gap is discovered later. Your Home Investment Plan sets out the full scope of works and the price in writing before anything begins, and nothing changes without a Contract Variation, documented, fully costed, discussed with you, and agreed in writing before work proceeds. No assumptions. No hidden extras. No unexpected invoices landing at the end of the project.

That figure is not a prediction that your project will run over. It is what covers the genuine unknowns that only reveal themselves once the ground is opened or a wall comes down, ground conditions that differ slightly from a trial hole, a drainage run in a different position than the drawings implied, or an existing wall needing more remedial work than expected before the new steel can bear on it. A fully specified quote, built from an actual site survey rather than a desktop assumption, removes most surprises before they happen. Contingency simply closes the gap between that fully specified quote and your final cost once those genuine unknowns are accounted for, and if it is not needed, it stays in your pocket.

Already been quoted a figure that feels suspiciously low against everything above? It is worth asking what has been excluded from it. Our free feasibility visit gives you a fully itemised comparison, with nothing missing, so you can judge any other quote fairly and avoid an additional cost turning up later that should have been priced in from the start.

Extension versus reconfiguring within the existing footprint

Not every household with a kitchen that does not work needs to extend the house to fix it, and it is worth genuinely weighing a reconfiguration against a full extension before assuming the bigger project is the right one.

A reconfiguration within your existing footprint, our £20,000 starting point, solves a layout problem. If the kitchen is a reasonable size but feels closed off, disconnected from the dining room, or awkward to move around because of where the walls sit, opening it into an adjoining room with a structural steel beam can transform how it feels to use without adding a single extra metre of floor space. It is faster, less disruptive and considerably less expensive than a full extension, and it is one of the more straightforward ways to save money if a full kitchen extension is not genuinely needed.

A kitchen extension, our £60,000 starting point, solves a size problem. If the combined space of your kitchen and any adjoining room genuinely is not enough for how your household wants to live, no amount of reconfiguring existing walls will create room that is not there. This is where genuinely new structure earns its cost, whether as a rear extension, a return extension, or a wraparound combining both.

The honest answer for most households sits somewhere in the diagnosis rather than the price tag, and weighing extension costs against a reconfiguration budget honestly, before any drawings are done, is the right first conversation to have. At the feasibility visit, we look at your existing layout and ask what is actually wrong with it before recommending either route, and we would rather tell you a reconfiguration will solve your problem for £20,000 than sell you a £60,000 extension you did not need. Our types of kitchen extension guide sets out the fuller range of options between these two starting points, including a return extension and a wraparound where a plot suits it.

Is it worth it

A well executed kitchen extension is consistently one of the projects that adds the most to how a home actually functions day to day, not just to its resale value, because the kitchen is the room a family spends the most waking hours in. Kitchen extensions are also consistently among the features UK buyers say they are looking for when viewing a home, which is part of why a well-built one tends to pay back more of its cost than many other home improvement projects.

Extension costs are only ever fairly judged against the alternative of moving, and moving house to solve a kitchen problem is one of the most expensive ways to solve it. Stamp duty, legal fees, removals and the compromises of a different postcode can easily add up to £30,000 or more before a single wall has changed, and that money adds no value to the home you already live in. For most households, the kitchen they are picturing is achievable in the house they already own, for a smaller total outlay and considerably less upheaval.

The honest caveat is that a kitchen extension is worth it when it is built properly, with foundations sized correctly for the ground, steelwork calculated by an engineer, and proper sign-off at every stage. A project built on day-rate subcontracted labour without proper oversight can end up costing more to put right than it would have cost to build correctly the first time, and that is not a risk worth taking on the room your household relies on most. Building with our own in-house team, under one contract and one dedicated Site Manager, is how we keep that risk, and any hidden costs it can bring, out of your project.

Is a kitchen extension definitely the right project for your home, or would a smaller reconfiguration or a garage conversion get the same result for less? That is precisely what the free feasibility visit answers honestly, before you spend anything on drawings.

We design and build across Bristol, Clevedon, Weston-super-Mare, Portishead and Clifton, with more than 30 years designing and building homes across the South West, our own in-house team, one contract and one dedicated Site Manager accountable from your first visit to your completion certificate. If a kitchen extension is not the right answer, we will say so at the feasibility visit and point you towards whichever project, a reconfiguration, a garage conversion, or a loft conversion, genuinely solves your problem. Our kitchen extension ideas guide is the next place to look, and our guide on how to choose a kitchen extension company sets out the questions worth asking before you sign anything.

Frequently asked questions