How much does a kitchen extension cost?

Thinking of extending? Here’s what you need to budget for.

If you’ve decided it’s time to extend and get the kitchen of your dreams, knowing what to budget for can be challenging.

From appliances to flooring, even the smallest of kitchen extensions involves a lot of work and materials, meaning costs can quickly escalate.

Credit: Plus Rooms

To help you with your project, we spoke to an architect and a design-and-build firm to get the best advice on how much it costs to build a kitchen extension.

The three main areas that affect your cost

Design, size and type of extension

It can be easy to get carried away with your kitchen aspirations when you gaze at images of bespoke kitchens, drool over handmade cabinets and marvel at sleek appliances.

But while the interior is clearly a vital part of your extension, it’s important not to forget the construction costs.

According to James Bernard, director at Plus Rooms, it’s estimated a kitchen extension can cost anything from £65,000 to £120,000. Architect, Riccardo Fabrizio from HiiGuru puts an average starting figure at £40,000, excluding the cost of the kitchen.

“It depends on the size of the extension,” he adds, “but it can go up to £150,000 depending on the size.”

Both note that location is also a factor. London residents can expect these costs to be higher.

kitchen with navy cabinets herringbone wooden floor and yellow blindCredit: Tholos Architects
Expect prices to vary depending on personal choice and style

So why does the cost vary so widely? Personal choice of size, type of kitchen and any design features all influence the final price, but if you set aside anywhere between £1,500 and £2,500 per square metre to work with (excluding design costs), you’ll give yourself a good starting point.

On the plus side, Bernard tells us a kitchen extension can increase the value of your home by as much as 20%.

neutral colour kitchen and living room extension interior with glass roofCredit: Plus Rooms
Getting the right connection between the extension and existing house is vital

Choosing your kitchen extension

Side, rear, wraparound or conservatory – which one is right for you?

When it comes to deciding where your kitchen extension goes, you may be governed by previous development at your property. Planning permission and permitted development rights are two factors your architect or design firm should be keen to discuss from the beginning.

With applications taking anything from eight weeks upwards, you need to know just how long it will be before you can start. And the costs for planning permission or permitted development approval are also another item to add to your budget.

single storey brick extension exterior with black crittal patio doorsCredit: Plus Rooms
Costs will vary with size and location affecting price

In terms of which type is more expensive, it will once again come down to the design choices you make, although it’s common sense to understand that a wraparound could potentially be more expensive as it combines a side and rear extension into one.

Don’t forget to budget for lighting

According to Fabrizio, there’s a common item that homeowners often overlook when it comes to kitchen extensions, and that’s lighting.

“Quite often, there is a lot of attention towards the kitchen itself,” he says, “but usually homeowners forget to think about how the room will be lit.

“If we analyse the question from a designer’s perspective,” he explains, “it’s a space with different functions, so it ideally requires different lighting sets. Preparation requires one type of lighting, whereas eating needs something different.”

Natural lighting from windows can also be overlooked.

“A lot of people want large skylights,” he adds, “but often underestimate the costs involved and end up having to compromise with multiple standard size units to make it more affordable.”

Types of kitchen extension

Generally suitable for most house types, it’s also great for kitchen/diner extensions.

A good option if you have unused areas to the side of your property that won’t be missed if you add an extension.

A cojoined space that wraps around two or three sides of the house, creating a larger overall extension. This type of extension lends itself well to kitchen/diner/living room extensions.

Orangeries are often a great choice for a kitchen conservatory. The larger proportion of solid walls makes it easier to house cabinets and appliances.

How much does each kitchen extension type cost?

Cost varies depending on location and size

Design studio, Resi, has a helpful guide on its website for the different kitchen extension costs. This assumes a rear and side extension to be 30 square metres and a wraparound 45 square metres. All costs are estimates and exclude VAT.

Side return kitchen extension cost

Contractor Rest of UK   London  
  Low end High end Low End High End
Individual £43,313 £61,875 £52,000 £75,000
Small company £51,975 £74,250 £63,600 £90,000
Large company £56,306 £80,437 £68,250 £97,500


Ground floor rear kitchen extension cost

Contractor Rest of UK   London  
  Low end High end Low End High End
Individual £37,125 £61,875 £45,000 £75,000
Small company £44,550 £74,250 £54,600 £90,000
Large company £48,262 £80,437 £58,500 £97,500


Wraparound kitchen extension cost

Contractor Rest of UK   London  
  Low end High end Low End High End
Individual £64,968 £92,812 £78,750 £112,500
Small company £77,962 £111,375 £94,500 £135,000
Large company £84,460 £120,657 £102,375 £146,250

If you already have an idea about the type of kitchen extension you would like, you can use this or this tool from Resi to get more of an idea about the costs involved.

How much will I pay for an architect?

And what level of service will I need?

With kitchen extensions involving more than just a simple stud partition wall, you’ll likely need an architect or design and building company to help create your dream space. Relying heavily on the combination of successful construction, electrics and plumbing, a kitchen extension is far from being an easy weekend DIY project.

The costs for an architect can vary depending on location and the size of the project and the level of service they will be providing. As a guide, Fabrizio advises to allow 3-7% of the construction cost value – depending on how detailed the job is.

male architect leaning over desk looking at 3D model of buildingCredit: Shutterstock/Goodluz
Architect costs will vary but their value can be priceless

The level of service you choose is again influenced by the size and nature of your extension.

“When a project has more technical challenges,” explains Fabrizio, “I’d recommend having the architect on site because it gives you a greater level of coordination. It also ensures that the builder is not taking advantage of your potential inexperience.”

This level of service would engage the architect for the entirety of the project, from the initial briefing until completion and delivery. It includes technical design specifications and execution of the works, site visits and responsibility for ensuring everything runs to plan.

“But not all architects and clients want or need this level of service, particularly on a small, straightforward project,” says Fabrizio. “Maybe someone only wants two ideas and then they will leave the responsibility of the execution to the contractor if they have a good relationship.

If you choose this option, then expect to pay anything from £60 – £150 per hour for an architect advises Fabrizio, depending on the experience of the professional involved.

“If it’s a sketch and a general bouncing around of ideas, it could be somewhere between £200 – £400 per room,” he says, “but for a better return on your investment, it’s more sensible to build up a relationship with your architect to get that one perfect design at the end.

large luxury kitchen extension with marble custom made furniture and cabinetsCredit: Tholos Architects
Working with an architect could ensure the extension of your dreams

“The most important aspect of having an architect appointed throughout the project,” he adds, “is that the architect has the experience to guide all the other professionals, make sure everyone is updated with everything and no-one forgets anything essential.”

Where to spend and where to save on your kitchen extension

Don’t be afraid to combine flat-pack with bespoke

From flooring to splashbacks, kitchen paint colours to cabinet handles, the list of choices to make when it comes to kitting out your kitchen extension can be long and costly. Fabrizio believes the most important one to get right is the worktop and that it’s fine to make compromises on other items to get that final wow factor.

“One of the biggest costs in the kitchen can be the worktop,” he says, “especially if you are choosing a custom made one. Sometimes, to save money, I’ll recommend a client uses a standard flat pack kitchen cabinet system – giving them more to invest in the worktop and custom-made doors.”

Hidden costs

As well as creating the new structure and kitting out the kitchen, there can also be hidden costs that are easy to overlook.

One that Fabrizio encounters is unforeseen issues with boilers. Many are housed in existing kitchens and need to be moved to the new extension or re-housed in the property. Either way, it’s an extra cost that affects the final bill.

Although I would have loved to install a bespoke kitchen at my Grand Designs project, my budget didn’t permit this luxury. Instead, as Fabrizio discusses, I bought an off-the-shelf high street kitchen and topped it with a bespoke LG Hi-Macs worktop (similar to Corian but less prone to staining).

I hired an experienced kitchen fitter to install the kitchen, and a specialist laminate company templated and fitted the worktop. Given that the island unit was over four metres, it was important to get it done accurately and professionally.

Visitors always assumed the whole kitchen was bespoke, which is testament to what can be achieved when there is a good quality of workmanship.

Contractors – who do I need?

A kitchen extension generally involves most trades

Whether you hire a larger building firm that can cover everything or you choose to project manage and subcontract to individual trades, a wide range of skills are needed to build a kitchen extension.

model figures of tradespeople placed on drawings as if holding a meetingCredit: Shutterstock/Leifstiller
Even the smallest extension requires lots of skilled tradespeople

Tim Phillips, a senior quantity surveyor at HiiGuru suggests allowing the following day rates for each trade.

Tradesperson day rates

A builder or specialist groundworks company required to take care of the foundations for the new extension.

Day rate from £250.

Someone who can construct the walls.

Day rate from £300.

Depending on your choice of finish, you may need a roofer or specialist roof covering firm.

Day rate from £256.

Vital for running all the necessary wiring, connections and ensuring the new extension is linked to the remainder of the house.

Day rate from £320.

To install pipework and drainage for sinks and wet appliances such as washing machines, dishwashers and the kitchen sink. If you intend to use gas appliances or have to move or add a new gas boiler, make sure your plumber is Corgi registered to avoid using an additional tradesperson.

Day rate from £320.

Try to choose a window company that can both supply and install as it will give you a more secure warranty.

Day rate from £256.

For painting ceilings and walls in the new extension and refurbishing the area which housed your previous kitchen.

Day rate from £224.

If you opt for a bespoke kitchen, fitting will be included in the cost, but if you buy an off-the-shelf version, an experienced kitchen fitter will normally provide a more professional level of finishing – even on a budget range.

Day rate from £256.

From floors to splashbacks, it’s important to get a skilled tiler in place. Tiles laid in a shoddy manner with even slightly uneven lines will catch your eye every time you’re in the kitchen.

Day rate from £224.

If you’re choosing a standard off-the-shelf solution, it’s likely your worktop will be part of the package. For a more specialist surface material such as Corian, it’s best to use a specialist company as they will be experts in templating, cutting and fitting to a high standard.

Day rate from £256.

How to get the best prices from sub-contractors

Be precise and don’t make changes

If you choose to project manage your kitchen extension alone, one of your key priorities will be getting the best price. The best way of achieving this according to Phillips? Using a Bill of Quantities (BQ) and the services of a Quantity Surveyor (QS).

“By using a BQ as a control document you can ensure that all the builders are pricing the same items, says Phillips.  “The BQ is compiled on Excel into separate trade/elements by a QS, using all of the design information from the other professionals such as the architect and structural engineer.”

drawings laid on desk with rulers, tape, people calcualating sumsCredit: Shutterstock/Asso
A bill of quantities leads to more accurate tenders

The advantage of having a set BQ? The variance in quotations should be lower.   “I always advise clients to approach at least 4 contractors as a minimum at tender stage,” he adds, “following an initial ‘would you like to tender’ call some three to four months prior.

“This will drive competitiveness from the builders pricing the contract.  Freeze your design as early as possible as variations will cost more when the project is underway because the builder won’t then be pricing them in competition.”

Phillips’ top tip? “Iron out any unknowns in the project prior to agreeing a contract sum with a builder, the more anomalies you have in a project, the more profit opportunity for the builder. “

Sarah Harley

Written by Sarah Harley she/her


Since first picking up a paintbrush and experiencing the joy of re-decorating her bedroom in a questionable red, white and grey scheme as a young teenager, Sarah Harley was hooked on the world of interior design. This obsession even led to a real life ‘Grand Designs’ project in 2005 when she donned a pink hard hat and appeared on TV screens, project managing the renovation and extension of a Grade II listed 17th century Folly in South Wales.

Throughout her career, Sarah has gained an array of experience in several different roles, ranging from copywriting, PR, events management and photography to interior design and home staging. With her two passions being the written word and the joys of a beautifully designed home, Sarah’s mission is to open the door on the world of interiors, inviting readers in to help them work their way through the vast choice of products, ideas and trends so that their own homes can reach their full potential.

Away from work, Sarah fills her Pinterest boards with more ideas, dreams of where to travel, takes photographs and loves being by the sea. She has two sons and if she absorbed everything they said would also be a football expert. The fact is she is often more interested in the colour and design of the kit – but don’t tell them that.

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