Planning a kitchen extension – a step-by-step guide

If your kitchen is feeling cramped, outdated and too separate from other rooms in your home then you may well be planning a kitchen extension.

Whether you're looking for a swathe of extra space, or more light, there's a way to make this new building work with your finances, as there are extension ideas for every budget, so long as you have realistic expectations of what you'll be getting.

'The great thing about extending your home is the opportunity to create a brand-new feel to your house,' says Keith Myers, director at The Myers Touch. 'A well-designed extension will release free space and create flow in your home with clever zoning areas for cooking, dining and relaxing.'

As exciting as that all sounds the thought of taking on a kitchen extension can feel a little overwhelming. It's not just a brand new kitchen you need to think about. You've got to budget, plan and brief all sorts of trades, as well as live through upheaval and mess. Planning a kitchen extension takes time and patience. But where do you start?

Planning a kitchen extension step-by-step

We've complied a handy step-by-step guide that walks you through the process of planning a kitchen extension. From costs to construction and everything in between, we cover all the stages you need to consider when designing and building your dream kitchen extension.

1. Identify what you need first

'It’s important to consider the identity of the space and what it will be used for and who will be using it,' explains Keith Myers.

'One of the things we do with all our projects, especially for kitchen extensions, is to map out and reflect with the homeowner how they will use the space, while also honing in on the natural elements and bringing them to life with sky lights or large doors that open up into the garden,' agrees James Bernard, director of Plus Rooms.

'If you’re planning a new extension, consider how you can use the valuable spaces in your kitchen, such as any pantries, laundry spaces, storage, and corners that often go unused and untouched in order to create spaces that are characterful and unique.'

James Bernard

As director of Plus Rooms, James consults with the clients at their home to discuss their build requirements during which he agrees each individual design and arranges a detailed priced schedule to go to them. In his youth he spent time labouring on building sites; has had experience working with structural engineers, building inspectors and architects and previously worked as a Project Manager himself.

It's also worth considering the site on which you house sits, and how best to extend. 'There are two ways of developing your kitchen extension,' says Keith. 'The first is taking a view from the outside. This means the designs are based on the physical conditions of the exterior of the property. For example, there is a drain running at the back or there is limited space, so you design the space to fit within the physical constraints of the exterior. '

'The other way of creating the space you want is to design from the inside out, so you are designing your perfect interior space, and then wrap the extension around it. You may have some dead garden space to work with, an old conservatory or room in the side return - these are all great starting points for your kitchen extension design.'

2. Consider the kitchen layout

The kitchen layout needs to be decided early on so that all of the electrical and plumbing services can be positioned to suit your plan. Think about what you want from your extension, and therefore how much space you want your extension to provide. Do you need room for a kitchen-diner? Do you want to include a kitchen island?

Ensure your new extension will provide an adequate supply of natural light. It may not be possible to add windows to a side extension, so glass roofing may be a good option. You want your extension to add space to your home... but not space that's dark and uninviting.

It's really important to think this stage through thoroughly. The more detailed your plan, the more likely it is that your contractor will be able to bring your ideal kitchen extension into reality, and you'll know exactly what planning permissions you need.

Bear in mind that the more spacious your kitchen extension, the longer the process will take. A single-storey rear extension is usually the most planning permission-friendly option, often achievable under permitted development. Don’t swallow up too much garden otherwise you risk reducing your property’s value. A simple side extension that’s subservient to the main house is also planner-friendly and can widen a narrow kitchen without stealing precious garden.

Side-return extensions are a common choice for terraced properties, which often have a half-width kitchen tacked onto the rear. The section of garden to the side of the kitchen is called the side-return and can be utilised to create a kitchen the full width of the property. A side-return can create valuable wall space for cupboards and worktops. And it can still be light filled, provided you install a series of skylights in the new roof space.

3. How to budget a kitchen extension

Kitchen extension costs are probably at the forefront of your mind, and it's understandable why. There are a lot of variables that will impact the cost of an extension. As a rough guide though, you should be looking at £1,500 per metre square upwards of £2,250 per metre square. As a ballpark figure, a 30 metre square kitchen extension could cost from £45,000 to £67,500, but projects in London and for high build quality would more likely see costs creep up to £90,000 plus.

'An average extension for Plus Rooms is a side return or wraparound on a terraced property in London,' says James from Plus Rooms. 'Taking it to a builder's finish (not including decorating, floor or kitchen), it would typically cost between £80,000- £100,000.'

However, there are additional costs you'll need to factor in, too.

Fees for planning permission (£206 in England) and building regulations sign-off would also need to be included, as would any fees for an architect (approx eight to 12% of construction costs) or a structural engineer (£500 or more), if you choose to or need to enlist their help.

You might also need a Party Wall Agreement, which can hover around £1,000 or more in London.

But even if you have limited funds, you can enlist the help of an architect and builder to plan a kitchen extension that falls within your remit.

4. Choose an architect

Once you’ve decided on a style and space, look for an architect or designer who will be able to advise you on what’s possible, guide you through the planning process and help you work on a budget. Make sure your architect is RIBA Chartered and make use of recommendations from family and friends.

'The reason for hiring an architect, is for them to add value, proposing and conceiving ideas and thoughts you might not consider,' says Darren Bray, director of Studio BAD architects. 'A good architect, will be able to work with a budget and still deliver a fantastic space; utilising affordable design ideas and materials to ingenious ways. An architect should be able to be challenged and challenge the concept of project.'

Ideally, you should create a shortlist of three or four architects. Ask to see examples of their previous work and to speak with former clients. Your chosen architect will then undertake a site survey and present plans to you for approval.

5. Understand building regulations and planning permission

Once you have approved the architect’s plans, you will know whether the extension falls under permitted development, or if you need to apply for planning permission for an extension. Your architect should be able to advise you in this respect.

'Obtaining permissions are an integral part of the design development process you will go through with your architect', says George Omalianakis, kitchen extension expert at GOAStudio. 'It will help you make decisions on your requirements, starting with the overall layouts of your kitchen extension project, then "zooming" in to assess more detailed requirements about technical and structural requirements, finishes, fittings and materials, before finally preparing tendering information for builders to review and price before you are able to appoint a builder for your project.'

If your extension falls under permitted development, you will still need to obtain building regulations approval from a building control officer (BCO), also known as a building inspector. Building regulations apply to most work and ensure safety and energy efficiency. You can choose between a local authority inspector or private approved one, which may be quicker.

If you’re applying for planning permission and your house isn’t listed or subject to restrictions, your architect can submit the plans for you. Allow at least eight to ten weeks for the application to be processed. At the moment, many authorities are running over this timescale, so bear this in mind. You may also require approval under the ‘Party Wall’ Act, which is a wall that stands on either side of a boundary of land belonging to two or more owners. Works with foundations within certain distances of the walls also fall within the act, not just work to the wall itself.

6. Get a builder onboard

'Make sure you find a very good builder, usually your architect, can help with this and recommend someone they work with all the time,' suggests Darren.

When looking for a builder, try recommendations from friends and family. You could also post a job on Ratedpeople. As with choosing an architect, make sure to get references and check that they have relevant insurances and guarantees.

Costs vary for building works, and it is a good idea to get several quotes. 'Once you have planning approval, your architect will need to prepare a set of technical / Building Regulation drawings that can be priced by the builder and use to build from,' says Darren.

'This will typically take a couple of months, depending on the complexity of the extension. The builder will typically take a month to price / tender the project, so it's best to allow three to four months post planning. But you may need to wait for your chosen builder as good ones get booked up.'

7. Consult a kitchen designer early on

You can engage with a kitchen designer early on in the process. In fact, bringing them onboard at the pre-planning approval stage will only help the overall design of your kitchen extension.

'The approach of working closely with a homeowner and their architect early in the process also allows kitchen designers to have a greater knowledge of how a client envisages their new kitchen, but how they want it to enhance their lifestyle and family's needs,' explains Keith from The Myers Touch.

Then, once your architect has planned the basic layout of the kitchen for you, you can take your architectural drawings to your preferred kitchen company. They can then fine-tune the layout and come up with designs for your approval.

Layout finalised and supplier chosen, you'll then be able to ask for a detailed layout, wiring and plumbing plans. Have these ready to share with your builder in time for the next step...

8. Get started on site

Once you have planning approval, Party Wall Agreement and a kitchen is on order, the building work can begin. At this point, 'first fix' decisions, such as the position of walls, floors, ceilings, electrics and water pipes should have been finalised.

While preliminary works get under way, ‘second-fix’ design decisions and a tender can be made about finishes, light fittings and tiling. Allow plenty of time for flooring to be ordered.

You’ll need a contract with your builder and your architect can advise you on the type required. ‘Most contracts require staged payments against valuations,’ says Hugo Tugman, founder of Architect Your Home.

‘This means that your architect visits the project every payment period and issues a certificate to say what percentage of the total work is complete. You then pay against completed works.’

9. Final stages

Once the building work is finished, any snagging issues can be dealt with. Snagging refers to the knock-on structural and finish effects of the building settling back on its foundations after the work is completed.

Only when these have been done to your satisfaction should you make your last payment to your builder in return for a final certificate. Make sure that all electrical work, plumbing and gas supplies are signed off, too.

Before your kitchen cabinetry and appliances can be installed, you’ll need to lay your flooring. Fitting of your new kitchen should then take up to four weeks. After the cabinets have been fitted, your kitchen company will template the worktops, which should take around two weeks.

In the meantime, you can paint the walls and add fixtures and lighting. Then, once the worktops are in place, you’re kitchen extension will be ready to revel in!

FAQs

Can you extend an existing kitchen?

Yes, the chances are that you can probably extend your existing kitchen.

'The question is how can you extend it to make the new space work with the existing space', says Expert Residential Architect George Omalianakis. 'You want the extension to create an enlarged kitchen, dining, living, and even kids play area that opens up to the rear garden and that links to the rest of the house in an effortless way.'

He adds, 'you will need the experience of an expert residential architect to help you assess what works best for you, what works best for the property, and how it can all come together in a way that is sensible and meets your requirements.'

'When planning an extension, visit your kitchen designer with your plans after you have had your planning permission accepted', advises William Durrant, owner of Herringbone Kitchens. 'This should avoid the need to compromise on your design later on and your designer will be able to provide your builder with drawings of your kitchen design.'

Do you need permission to extend a kitchen?

Planning permission is usually one of the more difficult stages of how to extend a kitchen. You are likely to need a number of approvals for your extension, all of which depend on the type of the property, the location, and how the new extension relates to the adjacent boundaries with the neighbours.

'If your property has Permitted Development Rights (this often applies to non-Listed houses that are not in Conservation areas, but not to flats) you might be able to add an extension that needs no prior planning approval', says architect George Omalianakis. 'But you will be limited with what you are able to do in terms of design, as Permitted Development requires that you tick a number of boxes. It's also advisable to apply for a Certificate of Lawfulness to confirm your Permitted Development Rights.'

You will need Building Regulations approval from your local Building Control or from a private Approved Inspector. Building Regulations deal with a number of technical and structural matters including the overall insulation levels of your extension and of your home, fire regulations, structural safety, weatherproofing details etc.

'You will also need to deal with any relevant Party Wall matters if you build near the boundary with your neighbours', explains George. 'And if your property is leasehold then you will need to obtain an approval (often called License to Alter) from your Freeholder. It's best to ask a solicitor to advise on the terms of your lease and how you go about obtaining approval from your Freeholder.'

Lastly, if you live near a public drain, you'll need to run your plans through the local water authority as well. There's a lot to cover, but any chartered architect should be able to help advise you on the planning permissions of your extension, and you can keep referring back to GOV.uk for all the relevant info.

How can I extend my kitchen on a budget?

If you're wondering how to extend a kitchen on a budget, it might be worth considering small kitchen ideas instead of a full-blown extension. There are a number of cost-effective ways to make the most of the space you already have, and going down this route will save you a lot of time and money.

'Blinds work really well in kitchens as they can make your room look taller and, as they free up space either side of the window, they instantly make a room feel bigger', says Yvonne Keal, senior product manager for Hillarys. 'Also, you can instantly create the illusion of space by simply adding a mirror to your kitchen. Place a mirror opposite your window to reflect natural light around your kitchen and accompany with a light and airy colour palette to add to the effect.'

You can also elongate your walls by painting your skirting board the same colour as your kitchen walls. Try these simple hacks if you're still on the fence about whether to invest in a kitchen extension. They will make your kitchen appear bigger than before, and you might not feel the need to extend afterwards.