A kitchen extension can truly transform your home. From grand open-plan spaces to simple side returns, turning a cramped cooking environment into a spacious and welcoming space can be life-changing.
But, regardless of the size of your kitchen extension, it still involves costs, time and potential upheaval to your daily life, which is why understanding the fundamentals of what's involved is essential.
From budgeting through to choosing your professional team, we take you through the process to help you figure out what you need to do, and more importantly, how to get what you need from your new kitchen extension.
1. How much should I budget for a kitchen extension
Before getting into the details regarding the design and look of your kitchen extension ideas, it's important to understand how much money you will need to have available to cover your kitchen extension costs.
As a guide, while there will be a variance in final spend depending on the size, style and quality of the extension, as well as your geographical location, kitchen extensions can cost between £1,750-£2,350/m² of new internal space.
Rick Fabrizio, founder of Tholos Architects suggests taking the following approach.
1) Start with what you can or want to spend
2) Divide by 1.2 to see the amount excluding VAT
3) Subtract statutory (council, building control, etc) and professional fees (architect, engineer, party wall agreements etc) and this will give you a net project cost.
"The fee you can expect to pay for a Chartered Architect or small firm to take care of all the design stages – including surveying the property, looking after planning approval and designing the construction details and specifications, can be anything from £6,000 up to £12,000," notes Rick.
"The range is wide as it depends on not only the complexity of the job, but also allows for possible extra services such as interior design, 3D visuals and taking care of the bidding process with contractors."
There will also be building regulations and planning fees, insurance and so on.
Once you've totted up the sums, make sure you add at least another 10% for contingency. Your extension will almost always cost more than you expected it to, so it’s important to have a contingency fund you can fall back on.
Don't underestimate your plumbing and electrical costs
“One area that’s notoriously prone to cost overruns is supplying the heating, kitchen lighting and power,” warns chartered surveyor, Ian Rock. “It’s fairly common to underestimate how many lights, sockets and taps will ultimately be needed in new extensions, and this can often trigger unbudgeted charges for ‘extras’.
"Often very little thought is given to assessing whether the existing power and heating systems will be up to the job of coping with the additional load, too," he adds. "Therefore, before extending your existing services it’s worth giving them a quick health check too."
Your electrician will need to check the existing system to see whether rewiring is necessary. They will then return to carry out second fix electrics – such as connections to plug sockets – before the worktops are fitted.
A plumber will check that the existing pipework is in good condition. You will need to ensure you have both a hot and cold water supply, as well as a waste pump from the sink to the outside. Kitchen appliances, such as your washing machine and dishwasher, will also need to be connected to the water supply.
Rick is a seasoned RIBA Chartered Architect with over 15 years of diverse experience in the construction industry across the UK, Europe, and the GCC. Specialising in retrofit, residential design and project management, he has also cultivated expertise in modern interiors. An ardent supporter of regenerative architecture and sustainable living, Rick boasts extensive experience in the UK planning system and a keen interest in alternative construction methods.
Chartered surveyor Ian Rock MRICS is a director of Rightsurvey.co.uk and the author of eight popular Haynes House Manuals, including the Home Extension Manual, the Self Build Manual and Period Property Manual.
2. Will I need planning permission for a kitchen extension?
If you are only planning on adding a small house extension, then you may be covered under permitted development (PD) rights and therefore not require planning consent.
However, bear in mind that if your house is in a Conservation Area or national park, the amount of work you can do under PD is usually reduced and you may require planning permission.
You will also need to apply for listed building consent for any work to listed buildings. To be covered under PD rights, a single-storey extension should:
- Be a maximum height of four metres
- Not extend beyond the original rear wall of the house by more than six metres if it is an attached house (i.e. semi-detached), or eight metres for a detached home
- If you are adding a side extension, this must be single-storey with a width of no more than half that of the original house
If your design falls out of these conditions, you will require planning permission regardless of whether you are adding an extension or knocking down internal walls. If you have any doubts, you should check with your local planning department before proceeding with your plans.
Kitchen extensions and the Party Wall Act
If in building a kitchen you require work to the boundary walls between your house and your neighbours' homes, then you will also need to comply with the Party Wall Act .
As part of the process, you’ll need to serve a Party Wall Notice to adjoining neighbours. This is notice of the work you intend to do and should be served at least two months before work begins.
If they consent within 14 days to the work, then you can begin. If they don’t, you and your neighbour will need to appoint a party wall surveyor (this may or may not be the same company) to draft up a party wall ‘award’, which describes how work will proceed.
3. What building regulations approval will I need?
A kitchen extension will require building regulations approval to ensure that the minimum design and construction standards are achieved. For this you will need to send an application to the local authority, where you pay a fee and the building inspector visits the site at the various stages of the build and inspects the work as it proceeds.
Most kitchen extensions will need to meet a minimum set of technical standards.
These will include:
- Energy performance
- Structural integrity as most extensions require foundations
- Protection against falls and unsafe walls
- Electric and gas safety as most extensions require new systems
- Fire protection to ensure safe passage from your home to a safe external area
And, if you are looking at glazed kitchen extension ideas, or a kitchen extension with skylights, don't get caught out by the rule that states that the area of windows, roof windows and glazed doors must not account for more than 25% of the extension’s floor area. It's covered in Part L of the building regulations documents.
“The reason for this restriction is simply down to thermal efficiency,” says Ian Rock. “Since even quite advanced glazing leaks significantly more heat than the equivalent area of wall, which now need to achieve the stipulated minimum U value target of 0.18W/m2K (as covered in Approved Document L1B – Conservation of Fuel and Power of the Building Regs)."
If you wish to create a highly glazed extension, you'll need prove that the design won't cause more CO2 emissions than a less glazed version of the design.
4. What kitchen extension design should I choose?
The design of your kitchen extension will be dictated to a certain extent by the first three points we've covered, but getting the design right also involves taking a look at what you need, how the new extension will work with your existing home, and how it impacts on your outdoor space too.
The key? Taking a holistic approach to how the end result looks.
"The most important consideration is to design the interior of the extension in parallel with the exterior shell," advises Emily Newmarch, design consultant at Kitchens by Holloways.
"Too often, extensions are planned structurally before the kitchen layout is considered, which can compromise proportions, flow and functionality. Start by being clear about how the space will be used, whether it’s a kitchen-dining space, kitchen-living-dining room, or a multifunctional family area and work from the inside out," she says.
Size vs needs
Size is of course a key variable, but it's important not to underestimate the difference even a small kitchen extension can have. Even extending by as little as 1m or so can really help open up a space, giving you options to remodel the layout so that you can get more out of it.
"There’s no fixed minimum size for a kitchen extension," confirms Emily. "What matters is what the space achieves. In some cases, reconfiguring the existing ground floor can deliver the desired result without extending at all.
"A small extension can still be worthwhile if it unlocks better layout, light, circulation or storage, such as allowing space for a pantry, utility area or more usable kitchen layout. Simply 'adding a box' doesn’t guarantee a better space – thoughtful planning does," she notes.
"A designer will start by focusing on how the space will function day to day: seating requirements, circulation, sight lines, storage needs and how the kitchen connects to living and dining zones," explains Emily.
"Practical considerations such as the position of glazing, radiators, fireplaces, pantry space, utilities and door thresholds will all influence layout decisions. Designers will also consider the architectural style of the home, ensuring the extension’s proportions, ceiling heights and detailing complement whether the kitchen is traditional or contemporary," she adds.
Ask yourself what do you need from the extra space? Is it space for a utility room and downstairs WC, a kitchen diner, or to create a better connection between your kitchen and outdoor space?
Think carefully about glazing
Also think about ways of getting light into your kitchen extension, by looking at variables such as where the sunlight catches the kitchen throughout the day as this will all help determine where to locate it, how big to go and how to glaze it and shade it to prevent overheating (if it’s south facing).
Will full width sliding patio doors be the best option? Could a bank of rooflights help bring light deep into the floorplan, and ensure existing rooms still receive daylight?
If your kitchen extension is to the rear of the property, consider bifold doors that open to the garden design. The full-height glazing will allow in plenty of sunlight as well as offering views of the outside.
If you are choosing to add a side extension or are after more privacy, then opting for clerestory windows is another good design solution.
Get specific on details
Also drill down on the some of the details about how you currently or want to be able to use your kitchen, suggests Rick Fabrizio.
"For example, do you use cast-iron cookware, knead dough, deep fry, use special appliances, host your guests in the kitchen, use more fresh or dried foods, have pets, cook with your partner or children and so on," he explains.
"The reason for such detailed questions is that as they tell their story I'm able to start envisioning their need for kitchen storage and worktop space. I can start to predict how they will move around, interact with other rooms of the house and how much privacy they will need in the space.
"It may seem minute detail," says Rick, "but it is important to understand the anthropometrics of the space – that is the relationship between the physical elements and human body dimensions.
"In more simple terms, it's about making sure you don't have to step on a ladder every time you have to access a cupboard or open a window."
Broken plan or open plan?
While many people extend to be able to create a larger open-plan kitchen, this isn't the only option available. Broken-plan layouts can offer you more defined areas and hard divisions or partitions which can reduce noise and food smells, and provide a more intimate environment.
If this sounds more like the ground floor layout you need, look at how you can carve out corners where you can place the kitchen, dining table or even a snug. Options such as having a different floor heights or introducing half-height stud walls can all be architectural tricks that make your space easier to live in.
Kitchen island ideas that separate the work station units and the dining table, for instance, are the ideal way of creating a break between the two spaces. They can also help with your kitchen storage, and even give you the option of installing a hob and sink. Or, a simple breakfast bar idea may be all you need to zone the kitchen from the dining area.
Emily is a design consultant at Kitchens by Holloways, a design and build company who not only create bespoke kitchens, but also thoughtfully crafted renovations and extensions.
5. What professionals do I need for a kitchen extension?
Using an architect
Architects are often used for a kitchen extension, especially when the owners are looking for an innovative design. However, it's also possible that a simple kitchen extension can be designed by the likes of a design-and-build company or an architectural technologist.
Essentially, you’re after a designer with a range of skills that suit your needs. Word of mouth recommendations are always key, as is hiring someone you have a rapport with. That may well mean choosing an architect, but it might just as easily be a local house designer without any formal qualifications. Insurance is key, of course, but many non-architects have that, too.
What's important to remember is that whether you hire a range of individuals to work on the kitchen extension, or opt for a full service package from an architect, someone must be well versed in building regulations in order to take responsibility for creating and submitting the necessary drawings and plans.
Sourcing a builder
Whether you’re looking for a reputable builder to bring in their own subbies or sourcing individual trades yourself, personal recommendation is the best way to find a high-quality professional.
Remember, good word of mouth is one of the best forms of advertising in the industry, so happy clients from past projects will often be more than happy to give their builder a plug. When speaking to a builder, asking to speak to past clients can often provide you with reassurance you are hiring the right company.
Family, friends and neighbours are a good first port of call, failing that, your architect or designer should be able to recommend professionals they have worked with on successful past projects.
Once you’ve compiled a list of potential people, contact them for an informal chat about the project. Ask about their range of skills, experience and workload, using the conversation to try and gauge their level of interest in your project. For main contractors in particular, ask if you can speak to previous clients or see past examples of their work to ascertain the quality of the workmanship.
Official registration can also provide peace of mind. You can find out if the tradesperson is registered as part of a competent persons’ scheme, such as the Federation of Master Builders (FMB) for your contractor or the National Federation of Roofing Contractors (NFRC) for roofers, and so on.
Once you’ve spent plenty of time digging into the details and speaking to various professionals, you’ll be able to begin whittling down the list of people you want to bring onto your project.
When selecting builders to carry out the work it's always a good idea to avoid agreeing to a day rate based contract. Always agree on a fixed price where possible. If you've allocated a contingency fund, don't include this in the fixed price so that you have an extra pot of money if something unavoidable happens during the build.
6. How long does a kitchen extension take to build?
Project time for building an extension depends largely on whether you need planning permission or not, the overall size, the type of interior fit-out, and the specifications you choose.
A single-storey kitchen extension, for example, will on average take 12 weeks to construct, however, if you are specifying extras such as architectural glazing or remodelling the whole of your ground floor layout then this will naturally add extra time to your extension schedule.
FAQs
How much value does a kitchen extension add?
One of the key questions you may aks before starting your project, is does a kitchen extension add value? Even if you aren't planning on selling anytime soon, you may want to know the amount to help set your budget. After all, you may be reluctant to spend more than you will ever get back.
While the uplift in value will be dependant on the size and the benefit the kitchen extension adds to your home, some experts suggest you can expect a return of around 20%, while others are less generous, stating closer to 10%.
Either way, before working out your budget for a kitchen extension, consult an estate agent about the house price ceiling in your area to get a better idea of where you should be prioritising any home renovation spend.
Is a kitchen extension worth it?
If you have a small kitchen, a kitchen extension is one of the most valuable areas of your home you can extend to create a more usable space. Whether you're looking at a large wrap-around extension or kitchen conservatory extensions, incorporating a dining or living space into your kitchen can help free up room in the rest of your home.
It has the potential of a domino-effect, perhaps giving you a much needed home office space or the opportunity to create a guest bedroom. Once you change the layout downstairs, you can often rework the layout upstairs too.
So, if your main goal is to increase the volume of available space, extending will certainly offer value for money in comparison to the fees associated with finding and buying a new house.
How can I pay for a kitchen extension?
If you are considering how you can finance your project, there are several ways you may be able to fund a kitchen extension, including:
- Using your savings
- Re-mortgaging your home
- Credit cards (look for a 0% interest card)
- Take out a second mortgage on your home
- Unsecured loan
Each of these options has its pros and cons, but it's important not to take on more of a financial commitment than you're able to pay back. Failing to pay when refinancing against your home can lead to the bank potentially repossessing your home.
Keen to explore some more design options for your kitchen extension? For a light-filled addition to your home, take a look at these orangery kitchen extension ideas, or, if you prefer the look of wood, we've rounded up 10 oak frame kitchen extension ideas that perfectly fit the bill.
