How much does a kitchen extension cost?

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.

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.

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%.

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.

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.

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

Ground floor rear kitchen extension cost

Wraparound kitchen extension cost

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.

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.

“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.”

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.

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.

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

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.”

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. “