How Much Does a Kitchen Extension Cost in the UK?

Kitchen extensions in the UK can cost anywhere from £20,000 to £125,000. 

However, most homeowners spend an average of £30,000 to £60,000 to achieve their dream kitchen space. 

There are many factors which impact how much a kitchen extension costs. Learn from the experts here at WhatPrice to help you figure out what you’re likely to pay to get a bigger kitchen. 

How much does a kitchen extension cost in the UK?

With a kitchen extension, your budget will need to account for: 

• Groundworks 
• Building the main structure
• Plumbing, heating and electrics
• Kitchen units
• Internal decoration
• Roofing, doors and glazing
• Landscaping 
• Professional surveys
• Planning permission
• VAT

As you might expect, the size and specification of your extension will impact the costs of all of the above. Your location in the UK can also make the same service much cheaper or far more expensive. 

Average UK kitchen extension costs (2025 estimates)

According to our research, we found the average homeowner pays between £30,000 to £60,000 to extend their kitchen.

Various factors exist which means you could end up paying a lot more or less to extend your kitchen. However, it’s good to know that many of the key parameters are things you can control to align with your budget. For instance, the size of the extension and the level of specification.

As a result, it’s possible to get a kitchen extension for as little as £20,000, while a large, high specification project based in London can cost over £100,000. 

Remember, you should research the average property values in your postcode to help you decide how much to spend on extending your kitchen. While a kitchen extension can add significant value to your property, if you overspend, this will reduce your overall profit. 

Price ranges by size (small, medium, large)

Small kitchen extension (15m²): £20,000-£45,000

Medium kitchen extension (25m²): £35,000-70,000

Large kitchen extension (35m²+): £50,000-£125,000

Regional cost differences across the UK 

Every county in the UK has different costs of living, which will reflect the prices you’ll pay for any kind of building work. 

Across the board, the North East, Yorkshire & The Humber and the Liverpool region have some of the cheapest prices. However, London and the South East have some of the highest prices for labour and materials. 

If you live in a more expensive area of the UK and you’ll be hiring local tradespeople, be prepared to pay extra for your kitchen extension. You might want to consider outsourcing your labour or kitchen materials from elsewhere in the country to save money. 

Psst: Want to know how much a kitchen extension costs local to where you live in the UK? Try our free extension cost calculator! 

Kitchen extension cost per square metre

In a previous article, we revealed that the average extension is priced at £1,400 to £3,000 per m2. This data was based on the prices submitted to us by WhatPrice users, covering various types of extensions across the UK. 

Beyond your location, the specification will determine whether your kitchen extension comes in closer to the lower or higher end of the average prices. So, when quoting tradespeople, it’s important to state whether you’re aiming for a basic, mid-range or luxury specification. 

Example cost scenarios based on common extension sizes:

Project type	Size	Lower cost	Lower specification involves?	Higher cost	Higher specification involves?
Small kitchen extensions	15m²	£20,000-£25,000	A flat roof, basic kitchen (IKEA units, laminate worktop) and uPVC windows/doors.	£35,000-£45,000	Bi-fold doors, roof lantern, quartz worktop and bespoke cabinets.
Large kitchen extensions	35m²	£50,000-£65,000	Simple rectangular design, lean-to roof, standard glazing and a mid-range kitchen.	£85,000-£1000,000	Large open plan, steel beams to remove walls, high-spec glazing (sliding doors), underfloor heating and a premium kitchen.
Side return kitchen extension	25m²	£35,000-£45,000	Simple infill with flat roof.	£55,000-£75,000	Full side return with glazed roof, steel beams and high-end finishes.
Glass kitchen extension	15m²	£22,000-£30,000	uPVC/glass panels and a basic roof.	£37,000-£50,000	Frameless glazing, aluminium frames and a bespoke roof lantern.
Kitchen extension with skylights	25m²	£37,000-£50,000	1-2 small Velux windows.	£58,000-£70,000	Large lantern roof or multiple skylights with slimline frames.

Full kitchen extension cost breakdown

As mentioned, some homeowners (especially in London) spend in excess of £100,000 on a kitchen extension. 

But based on the average kitchen extension cost of £30,000 to £60,000, this is how your budget might work out. 

Service	Typical % of budget	£30,000 kitchen extension	£60,000 kitchen extension
Planning permission & building regulations	2%-5%	£600-£1,500	£1,200-£3,000
Decorating & Finishing (painting, flooring, tiling, lighting & final touches)	5%-8%	£1,500-£2,400	£3,000-£4,800
Design & architect fees	5%-10%	£1,500-£3,000	£3,000-£6,000
Plumbing, electrics and heating adjustments	8%-12%	£2,400-£3,600	£4,800-£7,200
Kitchen cabinets (including fitting) & appliances	15%-20%	£4,500-£6,000	£9,000-£12,000
Labour & contractor costs	25%-30%	£7,500-£9,000	£15,000-£18,000
Construction & materials (i.e. the shell, structure, roof and glazing)	25%-35%	£7,500-£10,500	£15,000-£21,000

As is the case with any type of building work, the cost of materials and labour will always make the biggest dent in your budget. 

The larger and more complex your kitchen extension is, the more labour and materials will be needed to build it. So keep this in mind when planning your extension, especially if your plans are likely to exceed the £30,000 to £60,000 UK cost averages. 

If your plans are on the grander side but you don’t have the budget to match, you might need to make compromises elsewhere. For instance, opting for an ex-display kitchen rather than bespoke joinery. 

Types of kitchen extensions & their costs

Kitchen extension type	Price range (low to high)
Rear extension	£37,600-£86,300
Side return extension	£5,000-£55,000
Wraparound extension	£27,000-£100,000
Kitchen diner extension	£30,000-£40,000
Orangery or conservatory kitchen	£30,000-£35,000

For this section, we’ve looked at all of the extension types that exist, including ways that can be used to add more space to your kitchen. 

Small side extensions can be done cheaply by adding a lean to extension, which starts at around £5,000. In this instance, you might not even have to add in the cost of kitchen units, especially if you are just making more room for dining furniture. 

Things get a lot more expensive if you’ll be extending your kitchen as part of a double storey extension. Large wraparound or rear extensions covering two storeys can cost in excess of £100,000. 

Thankfully, there are plenty of middleman options which will allow you to extend your kitchen and dining space in a way that doesn’t get near six figures. For example, small, square shaped kitchen diner extensions can be done for a modest amount. When paired with cheaper kitchen units and your existing appliances, this can greatly reduce the cost of a kitchen extension. 

Factors that affect kitchen extension prices

	What can this involve?	What pushes up the cost?	How to do it on a budget
Kitchen extension size	Deciding on the square footage to be added and where (i.e. to the rear or side of your property).	Opting for a very large building footprint. Or, extending your kitchen as part of a double storey extension.	Choose a smaller extension or consider knocking through internal walls to gain extra space to avoid building out as much.
Kitchen extension layout	Mapping out where all of your kitchen units and other built-in fixtures will go.	Complicated shapes or challenging planning restrictions.	Keep things simple and follow specialist advice.
Ground conditions	Determining what foundations are needed for your foundation based on the soil type and quality.	Poor soil conditions mean deeper foundations are needed.	Find out what you’re working with before you start building. This gives you the chance to adapt your plans if needed to keep your extension on budget.
Site access	Ascertaining how labour and materials can make their way to the build site.	Difficult access making trips longer or more complicated to do. May even require specialist equipment to lift items into place.	See how you can mitigate potential access challenges as much as you can before the work starts.
Structural work	Removing walls or adding beams.	Needing to structurally support your new kitchen.	Don’t knock through load bearing walls.
Material choices	Choosing a specification ranging from basic to ultra high end.	Going for a fully bespoke, hand made kitchen.	Shop wisely and consider ex-display kitchens or upcycling your existing units.
Custom and high end products or finishes	Items made just for your project rather than purchasing off-the-shelf.	The use of exquisite materials or anything bespoke.	Use bespoke items sparingly or not at all.

At the start, we told you how kitchen extensions can cost as little as £20,000, but they can also cost up to £125,000.

The above chart explains this large price fluctuation, whether you are planning modest changes or a grand transformation to your kitchen. As a homeowner, this also means you can control many of the aspects which impact the cost, especially if you research what your budget will or will not cover. 

Hidden costs you might overlook

One of the reasons why there is never a set price for kitchen extensions is that it very much depends on the ground and overall property conditions your tradespeople will encounter. 

There can be logistical challenges, but also updated building regulations from when the property was last renovated to contend with. Sometimes the issues will be obvious even to you as the homeowner. In other cases, the issue may only become apparent once the work has started.

A solid contingency fund is one of the best ways to protect your kitchen extension from lengthy delays or even major compromises. 

Moving a boiler or utility meters

During a kitchen extension, you’ll likely be opening walls, rerouting plumbing and installing new services. As a result, it’s the best time to relocate your boiler or utility meters if their current position isn’t ideal. 

The benefits of relocating a boiler include:

Frees up kitchen space: Boilers often sit in awkward spots (on walls or in cupboards). Moving it can free up wall space for cabinets, splashbacks or appliances.

Create a better layout: If your extension includes a new kitchen island or open plan design, relocating the boiler to a utility room, loft or garage keeps the main space uncluttered.

Noise reduction: Noisy boilers can indicate a problem. But even new and efficient boilers don’t offer completely silent operation. Moving the boiler away from the kitchen and dining areas can give you extra peace and quiet. 

Upgrade your existing boiler: If you want to change the type of boiler you have (i.e. combi to system), then you may require additional accessories such as hot water storage. Relocating the boiler out of the kitchen can free up space, especially if you can place the boiler in a utility area instead.

Psst: Buying a new boiler as part of your kitchen extension? Get the best quotes for a new boiler here at WhatPrice, or consider switching to a heat pump. 

Relocating utilities 

If your kitchen extension will be towards the rear or side of your property, the existing meters may clash with your design. By law, utility meters must remain accessible. If your extension blocks access, they’ll need to be relocated. 

You cannot move utility meters yourself. Instead, you must get the applicable provider to come out, or use one of their approved contractors to carry out the works.

The costs you should expect to move any of the following utility meters include: 

Gas meter: £400-£1,000
Electricity meter: £200-£800
Water meter: £200-£500

Make sure to plan ahead if you need to move any utilities as the lead times can be long. 

Upgrading electrics and plumbing

Extending a kitchen usually also means increasing the demands on both your electrics and your plumbing. To ensure your systems can keep up and that they are compliant with the latest building regulations, some upgrades may be needed.

Upgrades to electrics

Modern kitchens often have appliances such as integrated ovens, American fridges, dishwashers and wine fridges. With multiple smaller appliances added on top, older circuits may not cope with the demand. 

Likewise, contemporary kitchens tend to feature lots of downlights and pendants, plus under-cabinet LED lighting. While this creates a light and airy space, new wiring may be needed as a result.

Rewiring will also be needed if your existing wiring doesn’t comply with the current Part P standards of the building regulations.

Rewiring: £2,000-£4,000

New consumer unit: £1,000

Extra sockets: £100-£150 each

Downlights: £40-£70 each

Upgrades to plumbing

It’s a given that lots of water will flow in and out of your kitchen. But with an extension, it can create an even bigger demand for water and drainage. 

Layout changes to your plumbing can be required if you’ll be moving any appliances such as the washing machine or dishwasher. You might also be adding a kitchen island, or even underfloor heating which uses a wet system. 

Additionally, you may be replacing your boiler and adding a hot water cylinder to meet the increased needs of your property. 

Finally, old copper or lead pipes may also require upgrading due to safety or practicality reasons. 

New plumbing for kitchen appliances: £500-£1,000

Relocating a kitchen sink: £400-£800

Underfloor heating (wet system): £80-£120 per m².

New boiler: £1,500-£3,500

Drainage and foundations

The new structure which will form your kitchen extension will need to be supported with foundations. The type of soil surrounding your property and the overall quality of the ground conditions will impact how much your extension foundations will cost. 

In an ideal scenario, your ground will offer excellent stability meaning shallower (and therefore cheaper) foundations will surface. But, if the soil is clay, sandy or waterlogged, deeper foundations will be required. While standard foundations cost around £80 to £120 per linear metre, deeper foundations can add thousands onto the cost. 

Drainage is another hidden issue to consider. New kitchens often involve moving or adding waste pipes (for sinks, dishwashers or washing machines). Connecting these to your existing system might work. However, if your extension interferes with existing foul water or surface water drains, they may need to be relocated, diverted or built over with a specialist permit (i.e a Build Over Agreement).

Also, if you’ll be adding a new roof, then you may also require additional surface water management to handle the increased rain runoff. So, now might also be the perfect time to replace your gutters. 

VAT, insurance & warranties

Any talk of VAT might make you groan. But it’s good to know what applies to your project so that you don’t face hidden costs. Plus, there can be ways to use VAT to your advantage during a kitchen extension. 

The standard rate for VAT is 20%. When collecting quotes, you need to check whether VAT has been included or not. If you use a VAT-registered builder, they reclaim VAT on materials meaning you’ll only be charged VAT once. 

Did you know that if you’re renovating a property that’s been empty for more than 2 years, you can apply for a reduced VAT rate of 5%? Definitely check if your property qualifies if you’ve just purchased a doer upper! 

Additional considerations include insurance and warranties. Getting all of the requirements in place to ensure your site at the work itself is fully covered can increase the cost. However, doing so can avoid costly and frustrating headaches down the track. 

Things to check between your tradespeople and your own insurance include:

• Builder’s insurance (i.e. public liability, employer’s liability and contracts work insurance)
• Workmanship guarantee
• Manufacturer warranties 
• Home insurance (renovation work cover)

How long does a kitchen extension take to build?

Kitchen extension project phase	How long does it usually take?	Delays to look out for	Tips to keep things on track
Design and approvals	6-12 weeks	Planning applications taking longer due to objections. Plans requiring revisions. Waiting for a party wall agreement with neighbours. Slow response from architects or engineers.	Submit your plans as early as you can. Also involve your neighbours early to avoid hold ups with them. Vet your planning experts before hiring and keep on top of the project.
Site preparation	1-2 weeks	Long lead times on skips, scaffolding or key materials needed to get started.  Structural surveys uncovering unexpected issues relating to the soil quality.	Order everything needed as early as possible and be sure to confirm the delivery dates before signing on the dotted line.
Groundworks & foundations	2-4 weeks	Poor weather which impacts the ability to pour concrete.  Deeper foundations required to mitigate poor ground conditions.  The discovery of manholes, old pipes or cables. Waiting for building control inspections to be able to go ahead.	Plan your kitchen extension during the months when the likes of heavy rain, cold temperatures and high winds are less likely.  Arrange ground surveys and building inspections in advance.
Building the main structure	3-6 weeks	Contractor availability. Material shortages.  Poor weather conditions.  Making last minute changes to the design.	Again, plan the work wisely so that the weather won’t halt the work.  Also, secure contractors early and keep an eye on the scheduling.  Order your materials in advance and have a backup option available where feasible.  Take the time to get your original design right to avoid hasty changes.
Windows, doors & roofing	1-2 weeks	Long lead times for manufacturing. This includes when items are bespoke or imported from abroad.  If the wrong items have been ordered.	Order glazing at the start of the project and double check measurements before placing orders.
First fix	1-2 weeks	Electricians or plumbers not arriving when scheduled. Hidden issues with old wiring or pipework needing upgrades. Waiting on building control approval before plasterboarding.	Book your chosen tradespeople early and confirm the dates as soon as possible.  Leave a contingency in your budget for unexpected issues.  Or, consider upgrading all of your wiring and pipework in advance of extending the kitchen if the property is in a poor state of repair.
Plastering & drying	1-2 weeks	Plasterers running late from another job.  In cold or wet weather, it can take longer for plaster to dry. Until it’s fully dry, you can’t paint it.	Choose your plasterers wisely based on their reviews but also their communication. If they give you the runaround, you will need to find new plasterers. Follow the advice of your plasterers to speed up the drying time.  If you plaster during the times of the year when you can open the window, this will always be best.
Kitchen installation	2-3 weeks	Missing or damaged kitchen units.  Trades clashing due to poor scheduling.	Inspect deliveries as they arrive and keep track of lead times.  Create a schedule of the work and continue to communicate with everyone involved.
Finishing touches	1-2 weeks	Snagging taking longer than expected. Waiting on final appliance deliveries. Decoration taking longer to complete due to plaster not fully drying. (Remember, your newly plastered walls will require a mist coat before painting!)	Create a snag list which can be sent to the applicable people. Ideally, flag any issues while trades are still on site. As with the other delays, keep an eye on timeframes and keep in regular communication with your team.

Excluding any planning time, it can take 2-4 months to build a kitchen extension. Thankfully, some jobs can run concurrently, although others (i.e. waiting for plaster to dry) will require a little patience. 

By getting organised ahead of time and also taking charge of the project management, you can look to reduce delays as much as possible. This is important as delays aren’t just frustrating, they can also add to the total costs. 

Do you need planning permission for a kitchen extension?

You don’t always need planning permission for a kitchen extension. For instance, if you are planning a small and modest kitchen extension, your plans might be covered under permitted development. While building regulations will still apply, planning permission won’t be needed. 

However, if your plans fall outside of permitted development, you’ll need to obtain planning permission to extend your kitchen.

Requiring planning permission isn’t the end of the world, but it will mean your project will take longer to complete. There will also be some additional associated costs. 

It’s your responsibility to check your plans with your local council before going ahead to see whether or not you will need planning permission. 

Permitted development rights explained

Permitted development rights (PDR) cover a set of planning rules which allow you to make changes to your property without needing full planning permission. PDR covers various types of home improvements including extensions. The aim is to provide homeowners with size, height and design limits to build within. However, once any single limit is exceeded, the work will need planning permission. 

If you want to keep your kitchen extension on the cheaper side, then staying within permitted development rights is advised. Though, this might not be feasible for all projects, especially if you are looking to maximise the value gained by extending.

When full planning permission is required

A kitchen extension will need planning permission when any aspect falls outside of permitted development rights.

Typically, this is when:

• You’re extending more than just your kitchen (i.e. a double storey extension)
• The structure will be taller than 4 metres
• It’s a side extension that will be half the width of the original house
• The new extension would cover more than half of your garden
• You’ll be building at the front of the house
• You plan on using different materials that will change the character of the building
• You are based in a conversation area or your property is listed 

Different rules can also apply depending on whether your property is detached, semi-detached or a terraced home. In short, the closer you plan on building to neighbouring properties, the more likely you are to face restrictions or even possible objections from your neighbours. 

Other legal considerations (party wall agreements, conservation areas)

If you’re building close to your neighbour’s property, then you may need a party wall agreement. The cost of hiring a surveyor averages at £150 to £200 per hour plus VAT. 

As you might expect, the grander your plans, the more getting a party wall agreement drawn up will cost you. That said, since kitchen extensions are single storey extensions, they are not as complex compared with double height extensions. 

Also, if you live in a conversation area or a listed building, then you’ll also need planning permission as well as approval from the relevant parties. 

Finally, if your kitchen extension involves building over or near any utility works such as drainage, then you will also need to get permission from your suppliers before going ahead. For Southern Water customers, this is known as a Build Over Agreement. Failure to get the required permissions for your kitchen extension can result in hefty fines, so don’t skip this step! 

Cost saving tips for kitchen extensions

Want to reduce the average cost of a kitchen extension? Discover these cost saving tips from the WhatPrice team. 

Smart design choices

When designing a new kitchen, it’s easy to get carried away with grand ideas you see on social media. In reality, you must respect your budget when designing your kitchen and choosing all of the interior finishes, otherwise your costs will spiral out of control. 

Keeping things in check doesn’t have to mean a total compromise. Instead, the key is to get smart so that you can create your dream kitchen which looks like you spent a lot, without actually doing so. 

Ways to cut labour costs

With labour taking up 40% of the average kitchen extension cost, you should look at ways to avoid spending more than is necessary. 

There is such a thing as going too cheap with who you hire and the project ultimately costing you more. But, there are always ways that your labour can blow the budget if you’re not careful.

So here’s how to strike a good balance:

• Get at least 3 quotes
• Provide your tradespeople with a detailed job spec so that the quotes will be accurate 
• Take on anything you are capable of doing yourself from site clearance to cleaning jobs
• Be on hand for deliveries
• Project manage to keep things on track, including scheduling the contractors
• Shop around for fixtures and fittings to manage the costs 
• Opt for standardised designs to keep things simple 

Reusing or sourcing cheaper materials

Before you rip your existing kitchen out, is there any chance the cabinets can be resprayed, or the worktop replaced? If so, upcycling your existing kitchen could save you thousands on your project. 

It’s also possible to buy flat pack furniture to provide additional storage or seating space, without necessarily having to start from scratch. 

Even if you do crave a blank canvas, you can get savvy with how you source your new kitchen. In short, this involves avoiding many of the main kitchen retailers in favour of independent companies, as well as ex-display showrooms. 

Doing some tasks yourself (DIY vs pro)

If you’ve spent any time on social media lately, you will have seen everyday homeowners just like you taking on renovation work to save money. While there are definitely some jobs that are best left up to the pros, doing what you can to move the project along can save you some cash. 

Depending on your skill level, some tasks you might want to attempt yourself include:

• Removing existing kitchen cabinets, tiles, flooring etc
• Stripping wallpaper or paint
• Painting and decorating
• Flooring (especially laminate or click lock flooring)
• Flat pack cabinet assembly
• Tiling the backsplash
• Landscaping 

Even basic clearance of your kitchen will save time and money. It can cost anywhere from £80 to £180 to hire a small skip, with larger skips priced at between £300 and £500 across the UK. 

Kitchen extension vs renovation – Which Is right for you?

There are many ways of transforming your kitchen which don’t include extending. The best option in your case is going to depend on what’s feasible with your current setup, plus your budget. 

	Average costs	Disruption	Best option when
Kitchen extension	£30,000 to £60,000	There can be a lot of disruption if the work is significant. But you may be able to isolate the area being extended so that you can still live at home. Extending will take longer to complete.	There is just no way to work with your existing kitchen space. You want to create an open plan space where you have more room for dining and inviting guests over.
Kitchen renovation	£15,000 to £30,000	If you will be knocking through walls, there can be a lot of noise and mess to contend with. But, renovating is far quicker than extending.	You don’t want to give up any garden space or don’t have the room to do so. Also, when you have a tighter budget that wouldn’t stretch to extending. Or, when your kitchen is big enough already, it’s just not to your personal taste.

When to extend your kitchen

In times gone by, kitchens didn’t used to be these vast open plan spaces. Instead, kitchens often allowed just enough room to cook in them, with the dining happening in another room. The concept of entertaining friends and family also wasn’t a thing back in the day. So if your property is older (especially if you’ve just bought it), you’ve probably noticed it’s not compatible with modern life. 

Extending your kitchen is the best solution when your current space feels cramped, but you also don’t want to take space from elsewhere to fix it. Likewise, when you crave an open plan living space, including when the aim is to maximise the value potential of your home. 

Advantages

• Increases the footprint of your home which will add the most value 
• Allows you to create your dream kitchen from scratch 
• Doesn’t require you to take space from elsewhere in your home
• Can greatly improve your quality of life (i.e. for family time and entertaining) 
• Extending allows you to contain all of the disruption to just one key zone in your property

Considerations

• It’s going to cost more to extend
• Will reduce your outdoor space 
• More likely to require planning permission 
• Building an extension takes longer 
• The areas around your extension will need landscaping (i.e. from bare soil to a patio)

When to knock through or reconfigure 

Could you ‘borrow’ some space from your existing layout to create a larger kitchen? Sometimes, this is absolutely doable, especially if your downstairs layout lends itself well to being rearranged. 

Granted, you may need to add some structural support if you’ll be making major changes to any load bearing walls. But, knocking through existing rooms could give you the kitchen of your dreams without having to extend the footprint of your property. 

Advantages

• Will be quicker to complete compared with extending
• Ideal if you don’t have room to build out into the garden 
• Less likely to require planning permission
• Gives you a chance to address a poor layout elsewhere downstairs  

Considerations

• No increase in square footage which will impact the total value added 
• Structural changes need to be accounted for (i.e. with steel beams)
• Will need to renovate all areas to be changed, rather than containing the work to the extension 
• May increase noise and reduce privacy between downstairs areas 

How to get accurate quotes

Your builder quotes will have a huge impact on your total kitchen extension cost.

Our research has found that builders quotes can vary as much as 20%-40%, simply due to the level of information provided. So it’s essential to get things in order before you invite builders to quote your job to avoid any miscommunications. 

What to include in your brief

The best way to get accurate quotes for your kitchen extension is to provide a clear specification of the work needed. 

Here’s what to consider: 

• The type of kitchen extension you’d like (i.e. rear, side or wraparound)
• The size of extension you want to achieve 
• Detailed drawings (i.e. from an architect or structural engineer) 
• What you don’t like about your current kitchen
• What you’d like to achieve from a kitchen extension 
• Scope of work (i.e. everything that needs doing!)
• If external work also needs to be included 
• Specification level
• Your budget 

If you’re at the early stages of seeing what’s possible, you might not have drawings from an architect or structural calculations. But, it can be helpful to get these first, as well as a site plan which maps out the boundaries, drains and manholes etc. 

Comparing quotes fairly

When you get quotes for a kitchen extension, you might notice some large fluctuations in the prices given. 

Before ruling anything out, you need to ensure the quote is like-for-like. For instance, if one builder has quoted for electrics and internal decoration, but another hasn’t. Likewise, check that the specification is the same for each trader. 

The best way to compare quotes is to ask for an itemised bill so that you can see what’s been included. 

If a quote seems too good to be true, it probably is. The trader may cut corners or charge you for hidden extras, so beware. 

Red flags to avoid

Unfortunately, it’s not a given that you can trust every builder you meet. Unless you do your homework, you could end up hiring someone who won’t give your kitchen extension the time, energy and care it deserves. 

Some of the top red flags when hiring builders includes: 

• Pressure to commit (i.e. ‘this deal is only available today’)
• Large upfront payment request 
• Unwilling to put things in writing
• Wants to be paid cash in hand
• Poor communication
• Unwillingness to show details of insurance or professional accreditations
• Encourages you to skip building regulations 
• Their quote is significantly lower than others (why?)
• Anything seems off when you Google their business 

There are some red flags you’ll be able to spot when you speak with the builder in person, especially if they seem reluctant to answer important questions. However, you’ll also need to research the firm on Companies House and the wider internet. 

Crucially, if the tradesperson or company has been involved in unscrupulous practices, this should be very easy to find when researching their name, company and location online. 

Choosing a kitchen extension builder

Before you part with the average cost of £30,000 to £60,000 to cover the cost of a kitchen extension, you need to know you can fully trust your builder. 

Questions to ask your builder

It might seem like a hassle, but you need to quiz your builder to ensure they are the right person for the job. 

Knowing the answers to these key questions can save you money, not to mention stress: 

• What is your experience in kitchen extensions?
• Can I see some images of projects you’ve worked on?
• Who will be doing the work, your team or subcontractors? 
• Who will be managing the project? 
• How long will my kitchen extension take to complete? 
• Are you insured? 
• Do you have any professional accreditations?
• Can you give me an itemised quote?
• What will be the payment arrangement? 
• Are there any costs not included in your quote? 
• Will you handle the building regs and other approvals?
• Do you provide any guarantees of your work? 
• In your opinion, what’s the best approach for my project? 

Also, if there are any specific worries you have relating to your project, make sure you get in early with the questions. You need to feel confident that the builder can handle the issue, especially if your kitchen extension will be large or complex. 

Certifications and memberships (FMB, TrustMark, etc.)

Tradespeople can become members of various schemes to demonstrate they follow good professional practice. 

For builders specifically, this can include the Federation of Master Builders (FMB), National House Building Council (NHBC) and TrustMark.

It’s easy to overlook professional accreditations, but it’s one of the best ways to avoid rogue traders. That’s because the tradesperson has to meet certain standards to become a member of the scheme. 

Also, some schemes offer regulation for their industry, which can give you additional protection if something goes wrong and it’s the fault of the tradesperson. For instance, the Gas Safe Register will investigate if a Gas Safe engineer leaves you with a faulty installation. 

Reviewing portfolios and client feedback

If your builder is experienced, then they should have a project gallery on their website or social media pages to prove it. This can then help you decide if their work is up to scratch, not least when you can also view public feedback about the tradesperson while you’re there. 

Kitchen extension costs FAQs

Still have questions about the average UK kitchen extension cost? We’ve answered some of the top queries below.