Kitchen extension costs: what will you pay in 2020?

This is everything you need to know about kitchen extension costs for 2020

Kitchen extension cost: small modern kitchen extension with rooflight and sliding doors
(Image credit: IDSystems)

Kitchen extension costs vary depending on your project, but one thing that is certain for all kitchen extension types, is that you will reap the benefits of your newly converted space, once complete. 

This home improvement project will let you enjoy open plan living, whether you choose a single storey, conservatory, basement or side return kitchen extension. It goes without saying that extending a house in any way is an investment, but when the cost of a kitchen extension is outweighed by the value it adds to your property if and/or when you come to move, it's worth it. Not to mention, it offers you and your family greater flexibility and living room in your home, which is fundamental under all circumstances, but most especially in the current climate. 

There is naturally upheaval involved, even if you aren't starting from scratch, and it's important to establish your budget beforehand to ensure that this project runs smoothly from start to finish. Below, you'll find a breakdown of all the costs you should know about, including planning permission if needed, as well as ways to help keep a cap on spending.

We've also included a link to our extension cost calculator to give you an estimate of what your kitchen extension will cost you provided you're UK-based.

How much does a kitchen extension cost?

How much it costs to expand a kitchen all depends on how much work you plan to do. As well as build costs and professional fees, there will likely be the cost of applying for planning permission and getting building regulations approval to include also. Finally, you need to budget for the kitchen itself, including flooring and decoration.

When you are setting a budget for your kitchen extension, there will be a certain amount of flex in each stage, so we have broken the project down into cost areas. 

Our expert tips provide all the information you need to achieve your ideal kitchen extension, while ensuring you set a realistic budget (and then stick to it). 

How much are kitchen extension build costs?

As a general rule, use the following as a guide:

Single storey extensions: plan from around £1,500 per m² for building work for a basic single storey extension (read our guide to find out more).

A more individual extension, with bespoke windows and doors will cost from £1,900 to £2,200 per m².  

Higher specification finishes can increase costs up to £3,000 per m².

Redesigning work, such as reworking an interior layout is likely to cost £500 to £900 per m². 

Planning a conversion? A garage conversion will cost £1,000 to £1,250 per m²; cellar conversions, cost from £1,150 to £1,850 per m²; new basement conversions cost between £3,000 and £5,000 per m². Our comprehensive guides will tell you more.

Extra foundation costs will be incurred by difficult ground conditions, such as clay, peat, nearby trees or slopes. Ask a structural engineer (find one at (opens in new tab)) and your local authority building control for an idea of likely foundation type.

Top tip: ‘Small extensions under 15 to 20m² achieve no economies of scale, so costs are higher per square metre,’ says experienced renovator Michael Holmes. 

Kitchen diner extension cost: an exterior shot of this modern extension

(Image credit: Bruce Hemming)

How to control kitchen extension building costs

While you may have an idea of your ultimate kitchen design in mind, getting to grips with kitchen extension costs during the planning stage takes more time. You can start by using our extension cost calculator to quickly estimate how much adding a kitchen will cost you in your area, and here is some advice straight from the experienced renovator, Michael Holmes:

Agreeing an all-in rate, plus reasonable expenses and disbursements, gives greater control of costs for planning and construction design.

'If the architectural designer is retained to help put the project out to tender and appoint the builder under a formal contract, as well as to provide contract administration services, the fee will typically be a further three to seven per cent of the total contract value.' 

'For a more ad hoc site attendance, service troubleshooting or adding design detail during the build, it is reasonable to agree a daily or hourly rate.’

Find out how to make a new kitchen cost less by reading our guide.

Kitchen extension by Onestà

(Image credit: Jake Fitzjones/Onestà)

Generally, using standard building materials will help to keep costs down as builders will be able to negotiate better deals. Doors and windows in regular sizes rather than bespoke will reduce costs. But that doesn’t mean you can’t be creative with the design, for example by exposing roof trusses for an impressive ceiling, using an interesting bond pattern for bricks or, as here, setting bricks on end.

This extension (above) to an Edwardian terraced property features distinctive brickwork and includes a bespoke kitchen, from £40,000, Onestà (opens in new tab).

For information on how to cut the cost of an extension you can call on our guide.

Setting aside contingency funds for a kitchen extension

Let’s assume you have set a budget of around £18,000 for an extension measuring 4m x 3m at £1,500 per square metre, plus a new kitchen at £10,000, always add in at least another £2,800 as a 10 per cent contingency should anything unforeseen occur.

How much do kitchen extension professional fees cost? 

Design fees for a kitchen extension will range from three to seven per cent of the overall build cost. 

Planning drawings will cost a minimum of around £2,400 to £3,600.

A measured survey of the existing house will cost from £500 to £1,500, depending on the size of the property.

The fee for construction drawings that are sufficient to build from (and for building regulations approval) will typically cost the same as planning drawings, with a minimum of £2,400 to £3,600.

Structural engineer’s fees will range from £500 to £1,000, and are necessary to design the foundations, roof, any large span openings and structural alterations to the existing house.

kitchen with contemporary feel and glazing by brayer design

(Image credit: Brayer Design)

Do you need planning permission for a kitchen extension?

You can check whether you need planning permission for a kitchen extension in our guide to permitted development rights for extensions and extending without planning permission.

How much does planning permission for a kitchen extension cost?

If your kitchen extension needs planning permission, planning application fees will cost around £200, but what you'll pay will depend on what you are proposing and whether you are in England, Scotland, Wales or Northern Ireland. 

In England, a certificate of lawful development costs £234 (if in Scotland, Wales or NI, ask your local authority). If your extension requires planning permission, you may need the following additional reports:

  • If your project affects trees, a tree report, at a cost of £200 upwards;
  • If your home is within a flood zone, a flood risk assessment: £600 upwards;
  • Many local authorities require an ecology report: from £720 upwards;
  • In areas of archaeological interest, an archaeological report based on a watching brief during excavation: this can cost several thousand pounds;
  • If your home is listed, a historic building report is likely to be required.

large rear extension under permitted development, double-fronted Victorian home, Crouch End, London

Mulroy Architects (opens in new tab)addressed the challenge of small, dark ground floor rooms in this double-fronted Victorian home in Crouch End, London (opens in new tab), by adding a large rear extension under permitted development, creating a light-filled interior.

(Image credit: Dan Glasser)

What are building control costs for kitchen extensions?

Fees for building regulations approval will depend on the size of extension. ‘They are likely to range from £250 for a project of 1-10m² and £900 for 80-100m²,’ says Michael Holmes.

How much does a party wall agreement for a kitchen extension cost?

A chartered surveyor can arrange party wall agreements for your kitchen extension. ‘This will typically cost from £700 to £1,000 per neighbour,’ says Michael. ‘If your neighbour formally consents to the works, you can avoid having a party wall settlement and save on the fees.’ (See (opens in new tab) for details.)

kitchen extension with large skylights and steel frame windows photographed by Bruce Hemming

(Image credit: Bruce Hemming)

How much are kitchen extension design costs?

Kitchen extensions cost anywhere from £17 per m² to £144 per m², bearing in mind that costs can be much higher for a bespoke option. The costs of the design work may be included in what you spend on the kitchen itself, or reflected in your total architect fees.

Kitchen extension bi-fold door costs

Whether yours is a period home or a contemporary one with an extension to match, it's very likely that you'll be adding bi-fold or sliding doors – a dominant, expensive feature of many a kitchen extension. So what should you expect to pay? Factoring around £1,400 to £1,800 per metre is sensible. For more buying, pricing and design information about bi-fold or sliding doors, use our guide.

kitchen with contemporary feel and glazing by brayer design

(Image credit: Brayer Design)

Kitchen extension lighting scheme costs

A scheme from a lighting designer can be well worthwhile. ‘Operate ambient, accent and task lighting on different circuits, for control of zones and the freedom to alter the mood,’ says Luke Thomas, associate at John Cullen (opens in new tab), which charges from £102 per hour’s consultation.

Find out how to plan kitchen lighting in our expert guide.

Kitchen extension concrete flooring costs

Concrete flooring is on trend and hardwearing. ‘It can be laid both internally and externally, giving spaces impact,’ says Jonathan Reid, director of GreyMatter Concrete (opens in new tab). Expect to pay from £120 to £144 per m² for a 50m² 10cm-thick floor.

Find out more about choosing the best kitchen flooring for you in our guide. 

Kitchen extension tile costs

Tiles are an excellent way to make a statement. ‘There are so many options, from rustic terracotta to hand-poured encaustic tiles,’ says Harriet Roberts, co-founder of Bert & May (opens in new tab), which offers reclaimed tiles, with prices starting from £72 per m². However, if you shop at DIY sheds or larger chains, such as Topps Tiles (opens in new tab), you can find wall and floor tiles for as little as £10 per m².

Have a read of our guide to choosing kitchen tiles for more inspiration.

Kitchen extension heating works costs

‘If you have a relatively new and energy-efficient boiler, check whether it is powerful enough to handle the additional heating demand,’ advises Michael Holmes. ‘If your boiler is more than 10 years old, consider replacing it, as a more energy-efficient design will help offset the cost.’ A straightforward gas boiler replacement will typically cost around £2,300, according to the Energy Saving Trust (opens in new tab).

Find out more about heating a kitchen in our guide. Use our guides, too, to underfloor heating and to choosing a boiler to find out more. 

Kitchen extension decorating costs

Wall finishes and painting, including minimal tiling, cost from around £77 per m². The budget for flooring, laid, is usually around £24 to £52 per m².

‘Decorating is one of the easier DIY tasks for those looking to reduce costs of an extension,’ says Michael. ‘Skilled decorators tend to spend more time prepping than painting and this makes all the difference to the finish, so if you plan to decorate, don’t cut corners on sanding, filling, priming and undercoating.’

‘Tiling is a skilled job and, given the high cost of tiles, is not one to complete on a DIY basis unless you have the skill, time and a good quality tile cutter.’ If you think you're up to the job, our guide to tiling a wall is a great starting point.

‘Second-fix carpentry is another good area for the skilled DIYer,’ adds Michael. ‘Laying wooden flooring, hanging doors, installing skirting and architrave and fitting the kitchen itself are achievable tasks. Fitting worktops requires more skill and the correct tools for cutting out sinks.’

large contemporary kitchen extension at rear of terraced victorian house photographed by polly eltes

(Image credit: Polly Eltes)

How much will a kitchen extension add to the value of your home

A single-storey kitchen extension can increase your home's market value anywhere from 5 to 10 per cent

When working out kitchen extension costs, it's vital to consider how much the extension itself might add to the value of your home because it's wise to ensure what you spend on the extension doesn't outstrip the value added. 

It's really worthwhile speaking to local estate agents for a more accurate idea, but as a guideline, a single storey kitchen extension can add somewhere between 5 and 10 per cent to the value of your home; while double storey extensions with an extra bedroom may add up to 20 per cent. This is very dependent on the local market, the quality of the extension you add and many other factors – which is why it's worth speaking to a trusted local agent first. 

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Lucy is Global Editor-in-Chief of Homes & Gardens having worked on numerous interiors and property titles. She was founding Editor of Channel 4’s 4Homes magazine, was Associate Editor at Ideal Home, before becoming Editor-in-Chief of in 2018 then moving to Homes & Gardens in 2021. She has also written for Huffington Post, AOL, UKTV, MSN, House Beautiful, Good Homes, and many women’s titles. Find her writing about everything from buying and selling property, self build, DIY, design and consumer issues to gardening.