Kitchen Extension Design & Planning for Beginners – Here’s Where to Start

Developing a Successful Kitchen Extension Design

A kitchen extension is a major investment, so before diving in you must consider what you want to achieve from the extra space it provides.

Think about how often you will make use of the room, what exactly it will be utilised for and the overall style you want to establish. For example, ask yourself whether your cooking habits will require an elaborate setup, how many people will you be cooking for and how much space you need for appliances, and so on. Shape the design around your answers.

This extension by Welsh Oak Frame blends seamlessly with the original property. The house was renovated a part of the same project, resulting in a unified aesthetic

“One of the things we do with all our projects, especially for kitchen extensions, is to map out and reflect with the homeowner on how they will use the space while incorporating glazed features such as glass doors or rooflights to create a seamless indoor-outdoor connection. It’s all about being mindful of your budget and choosing quality materials that will work with and for you to not only create a space that you enjoy being in, but a space that will last forever,” says James Bernard, director of Plus Rooms.

Consider future demands, too – what you need right now will be different to what you want 10 years down the line. For example, can you easily convert the children’s homework or play area zone into a space for adults to relax in when the space is no longer required?

Bear in mind that creating any sort of extension is no mean feat, so it’s a good idea to get professional kitchen extension design advice from the outset. An architect or design and build company will be able to translate your requirements into a perfectly-tailored scheme.

This home in Dulwich, London, has been upgraded with a kitchen extension by design and build company, Plus Rooms. The project involved expanding the kitchen/living area into the side-return, creating a characterful open-plan family zone

A kitchen designer or your architect can work through the optimum layout for the new room, balancing how much space should be allotted to the various functions, whether you’re a keen cook who needs loads of cupboards and drawers for storage or you need entertaining space to have dinner parties for a dozen friends.

“When planning a kitchen extension, consider how you can use the valuable spaces in your culinary zone, such as any pantries, utility areas, storage, and corners that often go unused and untouched in order to create spaces that are characterful and unique,” says James.

If the extension design means that kitchen straddles both old and new areas of the house, you may have to work around rolled steel joists (RSJs) that will interfere with a straight run of wall units. A good designer will make it all look as seamless as possible. This will probably be the largest room in your home, so it’s essential that functionality isn’t lost.

Ensure that your kitchen extension design accounts for the basic requirements – is there easy access to the garden? Have you allowed for adequate storage? Is there space for a washing machine and dishwasher, or will you have a separate utility room? Every kitchen extension’s layout will be different, just as every property has its own quirks, but these basic elements are essential.

Getting the Kitchen Extension’s Layout Right

For most people the kitchen itself will be the important aspect, so select its location and layout wisely. It’s a good idea to position it where there’s most available wall space – too many windows or doors will limit the layout possibilities. Also make sure the kitchen isn’t a thoroughfare, which can be annoying at best and hazardous at worst – imagine children running past while you’re dealing with hot pots and pans.

This dilapidated Victorian house has been welcomed into the twenty-first century with a new side-return kitchen extension, masterminded by Oliver Leech Architects. It features exposed Dougals fir timber, plaster walls, brushed copper worktops and polished concrete flooring

Working triangle rules still apply to an open-plan kitchen – you should never be more than a few steps away from the fridge, oven, sink and prep area. Ideally you shouldn’t have to walk around your island or other pieces of furniture to access them. Account for movement requirements, too, don’t just try and cram fixtures together if you don’t have sufficient room.

The space between a run of kitchen cabinets and an island should be at least 1m, for example, and if you want a breakfast bar, stools will need at least 1.25m behind them. Try to retain a feeling of space, which is why you’re extending in the first place.

For example, if you’ve invested in lots of glazing to make the most of great views of the garden, then keep sightlines open from the moment you step in the room rather than blocking them with a kitchen peninsula.

Heating, Lighting & Ventilation for Kitchen Extensions

When drawing up a kitchen extension design scheme, you’ll have to factor in the essentials: heating, lighting and ventilation.

Heating options for a kitchen extension

Warming an open-plan kitchen extension presents particular challenges – you may have limited wall space and face the issue of fluctuating temperatures. The best option in this case is underfloor heating (UFH), which will create an even spread of warmth throughout the room and free up walls for cabinets and furniture. The most efficient choice of underfloor heating is a wet system, which will have plastic pipework running deep under the floor to the boiler.

The other possibility is a dry setup that comprises a network of electrically-heated wires that sit below the floor covering. This can operate independently of the main central heating system, which is handy.

Getting natural light into a kitchen extension design

One of the benefits of having an open-plan kitchen-diner is that you are not sacrificing natural light by having smaller enclosed rooms. In most cases, rear extensions will include some sort of full-height glazing – be it bifolds, French doors or sliding units – which provide easy access to the garden and create an even flow of light.

Rooflights or lanterns set within a flat roof construction can be used to drench the zone in sunshine, allowing brightness to filter through to the rest of the property. Glass roofs on side returns will have similar effect.

Influenced by a mix of Dutch courtyard paintings, traditional East Asian courtyard houses and monastic cloisters, the idea for this rear extension to a Georgian terraced house, by Turner Architects, was to zig-zag out from the existing building. Bifold doors allow the zone to connect seamlessly with the garden beyond. Photo: Adam Scott

Getting ambient & task lighting right

In addition to natural light, an artificial lighting scheme should be planned from the outset. You’ll need a mix of general ceiling lamps to illuminate the entire zone and task lighting for specific jobs, such as preparing food or working on a laptop.

You may want to feature a pendant fixture over the dining table or island unit to add an interesting focal point.

Spotlights over your work surfaces will provide good visibility while you’re cooking and under-cupboard lamps will add ambience and background illumination.

Set within the urban Highgate conservation area of north London, Emil Eve Architects transformed this five-storey Edwardian terraced house with a striking and impactful glazed kitchen-diner extension. The fixed glazing and sliding doors were supplied by IDSystems. Photo: Taran Wilkhu

Ventilating your kitchen extension correctly

You must also consider ventilation at an early stage in your project – you’ll usually have some sort of upholstery in a kitchen-diner, so you don’t want cooking smells to linger. There are numerous practicalities to consider for your ventilation unit, such as the power required, noise level, where it will be positioned and whether you want a ducted or recirculation model.

There are plenty of choices to suit your interiors, from sleek ceiling-mounted versions and feature pendant designs to professional down-drafters.

Extractors vary hugely in price. Ducted versions pass the air through pipes and remove it from your house – great for dealing with smoke and smells. Recirculation models channel the air through a filter and, as the name suggests, recirculate it back into the room. These are less effective than ducted versions, but are cheaper and easier to fit.

Common Issues with Kitchen Extension Designs

A lack of walls for kitchen cupboards can be an issue in open-plan kitchen extension designs, and washing machines, dryers and sinks are easier to fit against external walls, compounding the problem.

If that is the case for you, “we would usually recommend floor-to-ceiling cabinetry, or incorporating a kitchen island into your design,” says Sean O’Donnell, who is a kitchen designer with bespoke furniture company Burlanes.

“Islands not only provide additional storage, but extra worktop space too, as well as a breakfast bar and somewhere for the family to gather and sit, eat and socialise. Bespoke kitchen islands can be made up to 3m long and can also house integrated appliances.”

Gruff Architects transformed this Victorian home with a new, contemporary kitchen-diner extension. Light floods the extension through arched and pill-shaped glazing – by IQ Glass – which references the home’s period design details. Photo: FRENCH + TYE

A general lack of space for all the functions required is common. “If you want to cook, dine and lounge in your new room, be clever,” says Amy Conn, a designer from kitchen and furniture company Neptune.

“Swap a large dining table for a kitchen island with a breakfast bar, or build in bench seating around a small table, which will free up space for a sofa, too. Or maybe you could downsize your utility room into a couple of floor-to-ceiling cupboards in your kitchen. These will still hide away the washing machine, tumble dryer and all your cleaning bits and bobs,” says Amy.

This article was originally published in September 2021 and has been updated in October 2024.