How much does a kitchen extension cost to build?

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.

In our guide we take a look at extension costs in general and explain the additional costs of locating a kitchen in your newly enlarged space, along with taking you through the individual stages and elements of this kind of project in order to simplify the budgeting process. 

What will affect your kitchen extension costs? 

While our kitchen extension cost guide aims to give you the average prices you can expect, it is hard to give an exact figure. This is because the quotes you receive will be tailored to your individual project and your own kitchen extension ideas. The main influencing factors will be:  

• 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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How much will your extension cost?

It's the big question: how much does an extension cost? 

Although there are many variables to take into account, as explained before, there are some average figures you should bear in mind when getting started — these should help you understand the size and type of extension you will be able to afford and help you plan the right route for you. 

On average, the majority of extension projects come in at approximately £1,500-£2,250/m² of new internal space — excluding VAT, design fees, structural engineer fees and costs associated with planning permission and building regulations applications.

In terms of planning and building regs fees: “A figure of £800 would normally be an adequate amount for a 30m2 £50k extension,” advises Quantity Surveyor Tim Phillips. 

How much should I budget for a kitchen extension?

Kitchen extension costs depend upon so many variables, each of which can dramatically change the overall cost — even before you add on the additional fees and potential hidden costs, which we’ll consider later. However, looking at costs on a price-per-square-metre basis can give you a ballpark figure to allow you to see if a kitchen extension is potentially viable on your budget. 

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. 

Always remember to factor in premiums for those living in higher-cost areas such as London, where trades inevitably cost more. These estimates include everything you would expect in a standard kitchen extension – these costs per m² are average ranges based on data captured for completed projects.

These figures do exclude VAT, so unless your tradesperson turns over less than the VAT threshold, there will be a VAT charge at 20% on all labour and work carried out on an existing home. Materials will also attract a 20% VAT charge, too.

How do kitchen extension costs break down?

If we take the above example of a 30m² single-storey kitchen extension for someone with a budget of say £50,000, as an illustration, the key costs could be broken down into the following elements.

Once clients see an example breakdown, they can often immediately start seeing what’s important to them and where they can potentially save to spend on other areas.  

• Structure (foundations, walls and roof): £20,000
• Plumbing and heating: £3,500
• Electrics and lighting: £3,500
• Flooring: £1,500
• Kitchen units and worktops: £14,000
• Decorating: £2,000
• Bifold doors: £3,500
• Landscaping works/making good: £2,000 

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Are there any hidden costs to be aware of?

Most of the items in your budget will be easy to identify as they will be physically present in your finished project. However, there are other costs that are usually incurred before any of the construction begins, together with ‘hidden’ or not entirely obvious costs.

Additional items you will need to factor in include:  

• 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. 

Will a kitchen extension change my council tax band?

If you’re contemplating a substantial extension, be aware this has the potential to move your home into a higher council tax bracket.

How much do kitchen units cost?

Once you have got an understanding of how much your extension is likely to cost, you might well be left asking 'how much does a new kitchen cost?'

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+. 

Kitchen cabinetry in general has the greatest potential for cost variations in the specification and finish element of the budget. The kitchen itself can range from under £5,000 to £60,000 and way beyond if your budget is limitless.

How much do new worktops cost?

Worktop choices can range from a very basic laminate at £20-£40/m² to granite at £150-£400/m², quartz at £225-475/m² and Corian at around £500/m². Splashbacks have considerably different price options, too, from PVC or glass panels, stainless steel or tiling, through to quartz etc. 

How much should I budget for new kitchen appliances?

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+.

How much does kitchen fitting cost? 

When it comes to fitting a kitchen, unless you plan on doing this yourself you will need to factor in the cost of professional fitting. 

Your final installation costs will very much depend on the size of the space, the kitchen design you have opted for, your location and who you get in to carry out the work. 

However, to get a rough idea of how much installation will add to your kitchen extension cost, the average fitting costs of a kitchen measuring around 13m2 is approx. £3,500, including the removal of the old units, the installation of new ones, worktops and appliances, plastering, tiling and decoration.

How much does plumbing cost for a kitchen extension?

Many people find that plumbing will not be included in the quotes from their builders or kitchen fitters — so don't forget to factor this in.

Plumbing for a kitchen extension is usually carried out in two stages. First fix plumbing will involving installing the pipework to connect the water supply and the waste water drainage. Your plumber should check your existing system and work out the best method for adding a new supply and waste which may entail new pipework being laid under your floor or along walls.

Second fix involves the connection of appliances and taps — plus all pipework should be given a final check for leaks. 

Your plumber's quotes will depend on the scale of the project but expect to pay between £150-£250 per day. 

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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. 

What additional kitchen costs should I include?

Many of the above costs won't take into account essential extras that go towards creating a new kitchen — omitting them from your budget could mean nasty surprises later down the line. 

Additional costs to be aware of include:

• 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

How can I save money on a kitchen extension?

Quantity surveyor Tim Phillips offers his top tips for keeping costs under control when building a kitchen extension:

• 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