How much does a kitchen extension cost to build?

modern kitchen extension with kitchen island

(Image credit: bradley van der straeten / French & tye)

Planning on adding space in the form of a new kitchen? Kitchen extension costs can be a little unpredictable but our guide is here to bring clarity and help you get organised when budgeting for this exciting project.

Kitchen extensions are one of the most common type of home improvement, often adding value to a house instantly, allowing for existing spaces to be reorganised, bringing in extra natural light and providing a relaxed space to dine in as well as somewhere from which to work from home and entertain when the working day is done.

The size of your extension: The bigger the extension, the more you will have to pay
Whether or not you require planning permission: You may need to factor in associated fees
The specification you are aiming for: Any extension will need to be furnished, but in this case you have the obvious and unavoidable cost of the kitchen itself. As we’ll see below, the choice of specification and design can increase your extension costs by tens of thousands of pounds.
The price of the kitchen itself: Don't forget items such as flooring, lighting, ventilation and appliances
Your location: It is amazing how much quotes vary depending on where in the UK you are
How much work you carry out on a DIY basis: The more you can take on yourself, the less you will pay in labour costs
Whether you plan on using an architect or house designer: Fees will push up prices
Plumbing and drainage requirements: Your new kitchen will require a water supply and drainage for a sink at the very least. Once you then start adding in a dishwasher, possibly a separate utility section with a further sink and washing machine, or an American-style fridge-freezer with an ice and water dispenser, or the increasingly popular boiling-water tap, the plumbing and drainage costs rise accordingly
Electrical requirements: Every extension space will require new sockets and lights, but a kitchen will always require far more of both, particularly with today’s endless range of electrical appliances and potential lighting solutions. In addition, you will need a supply for a cooker and hob, extraction fan, fridge-freezer, microwave, dishwasher etc. You will also need a separate 32-amp circuit for the cooking facilities, either installed if you don’t already have one, or extended
Moving the kitchen: If you are relocating a kitchen rather than just extending your current one, the further the extension is from the existing kitchen, the more your plumbing and drainage costs will increase. Similarly, if you require a gas cooking option, your gas supply will need to be re-routed at additional cost. This can only be done by a qualified ‘Gas Safe’ engineer and may prove quite complex work
Unforeseen expenses: You will have repair and redecoration costs for the old space. Aside from the plastering repairs, painting and new flooring, it’s also likely that sockets and lighting will need to be relocated. You may need to block up an existing back door completely or replace it with a new window. If you are changing the space to accommodate working from home, you’ll need the necessary furniture for this. All these costs should be considered as part of your kitchen extension budget as works cannot be simply delayed until funds allow

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small kitchen extension in London — The owners of this Victorian terrace in London (above and below) have added a stylish, cork-clad kitchen extension. The build work cost them £51,000, although this included a garden room too. The kitchen fit out cost £4,500, including appliances. (Image credit: Chris Snook)

It would be sensible to budget for costs between £1,500 - £2,250/m² of new internal space. A 30m² single-storey kitchen extension could therefore range from £45,500 - £67,500. This is obviously quite a wide range, but it serves to highlight the amount of variables involved in this type of project. Luckily, there is huge scope to alter the overall cost significantly, depending on the choices you make for every element of the design, build and finish.

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small kitchen extension — Extending partly to the side of an existing narrow kitchen increased the footprint enough to stretch out the internal configuration to fit in a dining space and create a better connection with the garden.(Image credit: Bradley van der Straeten)

Design fees: Architects tend to charge fees between 3-7% of the build costs, but this can be as much as 15% if they are engaged to fully project manage the extension
Planning permission fees: The cost of a householder planning application will vary according to where you are in the UK, but as a guide the cost is currently £206 in England. You may not need to pay for planning permission if your extension is small enough to meet the definition of ‘permitted development’ but always check the position with your local authority prior to any work. If you are able to use permitted development rights, it is still advisable to apply for a certificate of lawful development as this proves the extension is legal. This will cost 50% of the relevant planning application fee for the extension, so £103 in England. The certificate doesn’t expire and is a cost worth incurring as it can provide instant reassurance for a future buyer. Permitted development rights also allow for ‘larger rear extensions’ to be built without planning permission, but you will still need to obtain prior approval from
your local authority at a cost of around £100
Listed building consent: If your home is a listed building or in a conservation area, then you will also need listed building consent (to avoid an unlimited fine or
even imprisonment). While this is free, your overall costs are likely to go up due to the increased cost of specialist materials and skilled labour
Survey fees: If you require planning permission, your local authority can insist on a range of additional surveys depending on your particular home. You may need a tree survey costing from £250, or an ecological survey such as a bat survey, costing from £400. If your home happens to be within a flood zone, the planning authority can also demand a flood risk assessment (costing around £350). Those living in areas of archaeological interest can face additional report requests such as soil investigation reports, starting at around £1,500 for a single dwelling possibly rising to thousands if on-site observation is required
Building Regulations Approval fees: Approval fees Building Regs Approval will be required to ensure that the minimum design and construction standards are complied with, including energy performance, electric and gas safety, drainage and structural integrity. The cost of approval fees will vary according to your local authority fee rates, the nature and size of the project you’re undertaking and the number of visits required. Check your local authority’s website for a fee calculator. Fees will start from around £200
Structural engineer fees: You will need a structural engineer to provide the structural drawings and calculations for the build, which will also need to be provided as part of the Building Regulations Approval process — these will need to be signed off before the work commences. Structural engineer fees can start from around £500 but will increase depending on the nature and size of the extension
Party wall: If you are building on or close to a neighbour’s boundary, you may need a Party Wall Agreement, costing on average £1,500 and around £2,000 in London. These costs are multiplied by the number of neighbours affected
House insurance: You will need to notify your insurer to check if your home will be covered for the extension works or whether you will need additional specialist cover. Failure to notify them could invalidate your policy. The extension is also likely to increase the rebuild cost, which can increase your annual premium
Waste disposal: Hiring a large skip can cost up to £400 per skip in London and £280-£350 elsewhere. Skip hire costs usually include the licence fee for placing the skip on a highway, but in larger cities, it may be impossible to use the highway and your property may have insufficient space to accommodate it. If you need to place the skip in a residents’ parking bay you will need to pay for the space to be allocated to you. The cost will depend on the various local authorities so make sure you check and budget accordingly as this can add hundreds of pounds
Preliminaries: These are the things you’re going to pay for during the build which won’t be there when you finish the project — aside from skips, think scaffolding, temporary fencing, cabins, materials store and even a mobile toilet, if required
Electrical upgrades: You may need to budget for a new consumer unit if the existing one or old fuse board has become damaged over time or simply doesn’t meet the increased power requirements. Your electrician may be required by regulations to upgrade the system to add new circuits
External requirements: Don’t overlook the cost of things required outside of the extension itself. If you have extended out over what was formerly your patio or decked area, this will need to be replaced. Also, if you envisage your bifold doors opening out seamlessly onto a patio or terrace of the same level, it may mean excavation or building up the ground level. Your garden will undoubtedly need some money spent on it after it has been used as a building site for the extension.

kitchen extension with blue freestanding island — The owners of this Victorian house needed a way to transform the dark, narrow kitchen — they added a small side return extension to create an open, bright and sociable space and saved money by carrying out as much work as possible themselves. The extension cost £35,000 to build, the kitchen cost £5,000, the flooring £1,500, the quartz worktops £1,000 and the decoration came in at £200. Their range cooker cost £2,300. (Image credit: Kasia Fiszer)

At the lowest end of the price scale, you should be able to pick up a flat-pack kitchen off-the-shelf for as little as £1,000, sometimes even less. Do be aware, however, that these kitchens rarely include worktops or appliances. Once all these other factors are taken into consideration, more realistic average figures for new kitchens tend to hover around the £8,000 - £10,000 mark, easily rising to £20,000+.

The sheer range and sophistication of kitchen appliances available today means your choices can add up to tens of thousands of pounds to the cost. You can get a basic oven and hob, fridge-freezer and dishwasher for under £2,000 or you can spend over £5,000 on a range cooker alone. If you are adding a utility room, you can spend £2,000 plus on just a washing machine and tumble dryer. Plump for an American-style fridge-freezer dispensing ice and cold water, and plumbed-in coffee machines, and your total appliance costs can reach £10,000+.

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small basement kitchen extension — (Image credit: Malcolm Menzies)

This basement flat (above and below) has been extended to create a bright new kitchen with a good connection to the garden. The building work cost £70,000, while the kitchen came in at £20,000. Professional fees ended up coming in at £10,000.

Kitchen taps: It is possible to buy basic pillar-style kitchen taps for as little as £20. Opt for a tap with all the extras, such as instant filtered or boiling water and pull out spray hoses and you could easily end up paying upwards of £400 for your new fitting
Kitchen wall tiles: While kitchen wall tiles can be picked up for as little as £7/m2 if opting for a simple, white ceramic design, remember to factor in the services of a tiler if not doing the job yourself. Tilers charge anything between £150-£300. Don't omit to factor in the cost of adhesive, spacers and grout
Kitchen lighting: A kitchen extension needs great lighting to work well and be a pleasure to spend time in. Downlighters are popular kitchen lighting ideas and these can be picked up for around £10 per light. You will need to bring in an electrician to fit them — in all likelihood you will have an electrician working on the extension anyway so they should include this in their quote
Kitchen flooring: At the most affordable end of the scale you have the options of vinyl or laminate from around £25/m², but opting for higher-end choices such as hardwood, stone or polished concrete can take the cost to over £100/m2
Glazing: Glazing costs will be impacted by the amount of glazing you opt for in the design, the size of each glazed area and the materials you choose, ranging from standard uPVC windows at the lower end of the scale to huge bifold aluminium doors at the other end. You may also be considering Velux type windows
Bespoke elements: When it comes to windows and doors and so on, a completely bespoke finish will push your costs to the highest levels. Items that come in standard sizes will have much lower costs as they are mass manufactured. Bespoke items also take time to procure and delay alone will add to your overall costs
Structural opening sizes: If you are opening up a load-bearing wall you will have increased costs in terms of structural support needed. The larger the opening, the higher the cost. Or you may already have large windows or a patio door in place, and can use the existing lintel
Construction system: The cheapest system is masonry, but costs will increase if you are using, for example, SIPs or a timber frame
External finish: Just as with internal finishes, your choice of external materials will impact cost, too — and the market value
Build route: How you choose to build your extension will impact cost. The above figures assume a contractor is being used but you can save as much as 30% on these costs depending on how much of the potential DIY/labour aspects and project management you decide to undertake
Site specific issues: Your costs may be impacted by things specific to your property. For example, nearby trees that may need specialist attention — check for any protected trees from the outset. Or you may need to build over a public sewer, meaning you’ll incur the additional costs (utility company plus legal fees) and time delays of a ‘build over’ agreement or the cost of redirection. You may also need to underpin existing foundations

Design around off-the-shelf items where possible —using standard plasterboard and window/door sizes can save hundreds if not thousands of pounds
Work closely with your architect to identify bespoke design elements that could be changed to more affordable but visually similar options
Consider reusing elements of your existing kitchen. If the carcasses of your existing cabinets are okay, just buy new doors and handles and maybe have your cabinets resprayed. If you are buying new cabinetry, advertise your old ones for sale as collection only, to recover some costs and save on disposal
If you’ve relocated your kitchen and don’t need to renovate the old space immediately, leave it alone until cash flow allows. Just be aware that it is more cost effective to get the works done while you already have the tradespeople on site

Tim Phillips

Tim is a quantity surveyor and runs Quantiv.uk. He has almost 30 years of experience across the commercial and residential construction sector. @timphillips71

Tim Phillips is an experienced senior quantity surveyor and estimator and has worked in the construction industry for over 35 years. He has worked on many varied projects in this time, for corporates, public bodies and private residential clients, managing multi-million budgets.

For the past 13 years, Tim has worked on a freelance basis, whilst managing his rental property portfolio. He has extensive experience of undertaking his own full-scale house renovations. He is also a speaker and expert at the Homebuilding & Renovating Shows.