The Complete Guide to Planning a Kitchen Extension
A new kitchen extension is one of the most valuable home improvements you can make. Beyond adding just space to your property, it’s an opportunity to enhance how you cook, dine, and socialise, creating a seamless connection between your kitchen & living space. A well-designed extension balances functionality and style, integrating beautifully with your home while increasing its value.
At KCA, we specialise in designing kitchens for extensive home renovations, many of which involve kitchen extension projects. This guide takes you through everything you need to know, from setting a budget and choosing the right layout to managing construction work and ensuring your extension project runs smoothly.
Table of Contents
Why Extend Your Kitchen?
A large kitchen extension is more than extra space—it transforms how you live. An extension can provide the perfect solution if your kitchen feels small, lacks storage, or doesn’t maximise natural light. A well-planned design improves flow, making your kitchen & living space more open and sociable.
Key Benefits of a Kitchen Extension
- More Space – Extra room for cooking, dining, and entertaining.
- Improved Layout – Enhances usability with open-plan designs.
- Better Style and Design – Updated materials, storage, and appliances.
- Increased Natural Light – Incorporate skylights, bi-fold doors, and full-height glazing.
- Higher Property Value – A well-designed kitchen extension can increase home value by up to 20%. Read this article for 7 home improvements that add value.
- Seamless Outdoor Connection – Large glass doors can improve indoor-outdoor living.
- Smart Home Integration – Upgrade with modern technology for better efficiency.
Types of Kitchen Extensions
Choosing the right extension is key to a successful project. Common options include:
- Rear Extensions – Extend into the garden, creating a spacious open-plan area.
- Side-Return Extensions – Utilise unused alleyway space, ideal for terraced houses.
- Wraparound Extensions – Combine side and rear extensions for maximum transformation.
- Orangery or Conservatory-Style Extensions – Use glass to maximise natural light.
Each option has unique benefits, and consulting an architect or builder can help determine what works best for your home.
Planning a Kitchen Extension
Every successful building project starts with a clear vision. Consider your extension’s style, size, and function early on to ensure it complements your home. Even a small extension can improve kitchen usability, while a large kitchen extension allows for open-plan layouts that integrate cooking, dining, and living areas.
Setting Your Kitchen Extension Goals
Before starting your building project, think about how you want your kitchen to function. If you love entertaining, an open-plan layout with a kitchen island and seating area may be ideal. If storage is a priority, consider a walk-in pantry, integrated cabinetry, and clever space-saving solutions. For those who enjoy indoor-outdoor living, large glass doors can help blend your kitchen & living space seamlessly with the garden.
Creating a mood board or wish list can help visualise your ideal kitchen extension design. Engaging a kitchen designer at this stage ensures your ideas are translated into a practical, well-executed plan. For inspiration, why not browse our extensive gallery of modern and traditional kitchens, or discover kitchen extension ideas from our designers.
Budgeting for Your Extension Project
Budgeting for a new kitchen extension requires careful planning. Construction and labour costs typically form the most significant portion of your budget, followed by the cost of kitchen cabinetry, appliances, worktops, and finishes.
Other important budget factors include planning permissions, structural modifications, and compliance with building regulations. We recommend setting aside a 10-15% contingency fund for unexpected costs.
Estimated Extension Costs (Checkatrade):
Basic extension cost 20m² £40,000 – £56,000
Standard cost for small extension 20m² £40,000 – £56,000
Standard cost for medium extension 30m² £60,000 – £84,000
Standard cost for large extension 50m² £100,000 – £140,000
Premium extension cost 30m² £75,000 – £110,000
If you need further budgeting and planning advice, why not read our blog How to Design Your New Kitchen With No Regrets
Designing Your Kitchen Layout
A well-planned kitchen layout balances efficiency and aesthetics, ensuring a functional and stylish space. Thoughtful design choices improve workflow, maximise storage, and enhance everyday usability.
A successful kitchen extension isn’t just about adding extra square footage—it’s about creating a space that truly works for you. The way the layout flows, how the space is used daily, and how it connects with the rest of your home can have a far greater impact than simply making it bigger.
A kitchen extension is an opportunity to fix any of those niggles you have about your current kitchen. Share everything that doesn’t work about your current kitchen with your kitchen designer, however small it may seem. The more detailed you can be, the more they will understand exactly how to design a new kitchen that will enhance your life.
Here are some examples of goals you could have for your kitchen extension:
- Reconnect a disconnected kitchen that forces the family to spend time separately in different rooms.
- Redesign the kitchen to better facilitate cooking preferences, perhaps move the ovens to eye height and add an extra combi oven for efficiency. Or, swapping the undercounter fridge for a full height fridge freezer.
- Create a dedicated utility room, so the laundry isn’t cluttering up other rooms and the laundry appliances can be moved from the kitchen.
- Add an extra downstairs WC, always a welcome addition to any family home
- Improve the space for socialising by planning an ergonomic flow whether it’s a fully open plan or broken plan kitchen.
- Make more space for cooking by increasing worktop area.
- Increase storage with more cabinets, drawers and storage solutions.
Appliance placement, lighting, and work surfaces should be carefully considered to create an efficient workflow.
Smart storage solutions such as deep drawers, corner pull-outs, and floor-to-ceiling cabinets help organise the space. A well-thought-out design ensures your extension project is both practical and aesthetically pleasing.
When to Engage a Kitchen Designer
From over 32 years of experience designing and installing kitchens, we’ve found that the earlier the kitchen designer is involved in the project, the better.
This allows time for your designer to give you valuable advice before planning is submitted and construction begins, reducing design changes later down the line and saving time and money. Whether your space is a narrow galley kitchen, an L-shaped layout, or a large kitchen extension, your design can be tailored to suit your cooking habits, storage needs, and lifestyle.
Managing Your Kitchen Extension Project
Some homeowners choose to oversee the project themselves, coordinating with builders, architects, and kitchen designers. However, hiring a professional project manager can help keep schedules, budgets, and communication on track for larger projects.
Another option is working with an architect who provides project management services. Many architects have strong relationships with builders and tradespeople, ensuring seamless coordination from design to completion. Alternatively, design-and-build companies handle both planning and construction work, simplifying the process.
It’s also beneficial to choose a kitchen company that works with builders, architects and interior designers. A kitchen designer that understands the construction journey will liaise with your trades directly, pro-actively share all information and co-ordinate as needed to ensure your project runs smoothly.
Choosing the right management approach depends on the scale of your extension project and how involved you want to be in day-to-day decision-making.
Finding a Builder for Your Kitchen Extension
- Choosing an experienced builder is crucial when undertaking any extensive home renovation.
- Seek Recommendations – Ask trusted sources such as architects or friends.Check Credentials – Verify insurance, certifications, and online reviews.
- Assess Previous Work – Look for quality and attention to detail.
- For more information, read our guide: How to Find a Trusted Builder for Your Home
Planning Permission & Building Regulations
Not all kitchen extension projects require planning permission. Some fall under Permitted Development Rights, meaning they can proceed without formal approval if they meet specific conditions. However, if a large kitchen extension exceeds size limits or is in a conservation area, planning consent will be required.
To be covered under Permitted Development rights, a single-storey extension should:
- Be a maximum of four metres in height
- Not extend further than six metres beyond the original rear wall of the house if it is an attached house (i.e. semi-detached), or eight metres for a detached home
- Side extensions must be single-storey, no wider than half the width of the original house
If your design doesn’t meet these conditions, you will need planning permission, whether you are extending or removing internal walls. If you’re unsure, it’s always best to consult your local planning department before moving forward with your plans.
Even if planning permission isn’t needed, it’s advised to apply for a Lawful Development Certificate (LDC). This confirms that your extension complies with regulations, which can be useful when selling your home.
At the time of writing, the cost for an LDC is around £103 for householder applications and £234 for non-householder or existing use/operational development. Planning Permission fees vary, starting from around £200 for householder developments, and can escalate substantially on larger extension projects.
Building Regulations for Kitchen Extensions
- Structural integrity
- Energy efficiency
- Fire safety
- Electrical wiring and plumbing
To get approval for building regulations, you must apply to your local authority and pay a fee. The building inspector will visit the site at various stages of the build to inspect the work.
A building control officer ensures that the minimum standards outlined in building regulations are met. If you are planning a kitchen extension, you must notify building control before work begins.
If your extension involves a shared wall with a neighbour, the Party Wall Act may also apply, requiring a formal agreement before construction work begins. Understanding these legal requirements early will help prevent delays and ensure a smooth process.
