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Kitchen Room Extensions: Everything you need to know


I love to cook!

It was no fun running around the kitchen while my friends and family were laughing away in the other room, though.

That has all changed since we decided to create a fantastic new kitchen extension.

We knocked through the dividing wall so the kitchen and living room are now the same space. It’s become the part of the house we spend the most of our time in.

It’s also fantastic that guests can sit and chat to me at the breakfast bar while I’m busy chopping away.

But the kitchen extension process can be a little complex, so I’ve created this useful guide for anyone who might be thinking about a kitchen upgrade at the moment.

Table of Contents

1. What kind of kitchen extension would you like?

This is the first question to ask when thinking of new kitchen extension ideas. It really depends on the type of house you have and your budget.

Side Kitchen Room Extension:  Some houses have spare space to the side of the property. Even a narrow side extension can help increase the width of your house to give you that much-needed extra space. By planning the new kitchen well, this option can transform even the smallest of living spaces into something spectacular.

Rear Kitchen Room Extension: If you have limited space to the side of your house then extending towards the rear is also a great option. In most cases, you can extend the full width of your house. That extra space cannot only help increase the size of your kitchen but also your living room at the same time.

Wrap Around Kitchen Room Extension: For those fortunate enough to have extra space to both the rear and side of your house, this option will give you the biggest kitchen possible. With this type of design, you might also have space for a utility room, huge kitchen island and breakfast bar.

2. How much does a kitchen room extension cost?

The cost of a typical kitchen extension will vary between £2,000/m2 and £2,500/m2.

This means that for a 30m2 extension the total cost would be between £60,000 – £75,000.

The above costs are just averages. It is also very useful to have a clear understanding of the more detailed costs associated with an average sized (30m2) kitchen extension. These include:

  • Structural elements (walls and roof): £30,000
  • Kitchen units and worktops: £15,000
  • Flooring: £1,500
  • Electrics & lighting: £3,000
  • Heating and plumbing: £3,000
  • Sliding patio doors: £2,500
  • Decorating and finishing: £2,000
  • Minor landscaping works: £2,000

3. How to control kitchen extension build costs

Architect vs no architect: This depends on the type of kitchen you would like. If you’re planning to replace an older kitchen with something more up to date, most high street kitchen companies will be capable of managing the entire project on your behalf.

If your new kitchen is going to be part of a larger extension, we would suggest contacting a local architect. They will be able to design a number of creative options for you to choose from, and they will have a huge amount of relevant experience to draw upon.

Contract administration: For peace of mind, your architect could also manage the entire construction process in addition to designing your new kitchen extension. This service would include:

  • Preparing tender documents
  • Prepare a builder’s contract
  • Weekly on-site inspections
  • Extension sign off

A new kitchen room extension can be a complex process, often with problems to solve along the way. For example, what if your builder constructs something slightly different to what is shown on the architect’s plans and you don’t agree with what you should do? If your architect was managing that process, they would simply arrange a site meeting with the builder and explain exactly how it should have been done.

While this option will give you peace of mind, it does come at an additional cost. Architects typically charge between 3% – 5% of the total construction cost to manage the process on your behalf.

Ad hoc architect assistance: Another option is to simply pay an hourly rate to your architect when you need their services during the construction process. Rather than attend the site every week as part of a more formal arrangement, using this option means the architect would only come to site when needed which can save money if the construction process runs smoothly.

Kitchen Quality: The quality of finish will have a huge impact on the total cost of your kitchen extension. For example, if you purchase your kitchen from a high street company (Howdens, Benchmark or Ikea) the carcasses and doors will often be made of MDF which is relatively inexpensive.

If you would like a bespoke made to measure kitchen, the company will probably use solid wood carcasses and doors which adds to the overall cost but might last longer.

4. Will I need planning permission for a kitchen room extension?

4.1. Kitchen Only

If you’re planning to replace an older kitchen with a new kitchen (with no external changes to your house) you would not need to apply for planning permission.

4.2. Rear kitchen extension

Many kitchen room extensions can be built through what is known as ‘Permitted Development’. These are certain types of extensions that do not require planning permission. We have made a checklist of the relevant criteria below. If you meet these requirements, your new kitchen would be Permitted Development. If you fall outside of this criteria, you would need to apply for planning permission.

Footprint size: Only half the area of land around the “original house” can be covered by extensions or other buildings (including any existing extensions or outbuildings).

Kitchen extension height: Extensions cannot be higher than the highest part of the existing roof, or higher at the eaves than the existing eaves (the area just below your gutters).

Proximity to the boundary: Where the extension comes within two metres of the boundary, the height at the eaves cannot exceed three metres.

Kitchen extension location: The extension cannot be built forward of the ‘principal elevation’ or, where it fronts a highway, the ‘side elevation’.

Materials: The materials used in any exterior work must be of a similar appearance to those on the exterior of the existing house.

Extension Depth: Single-storey rear extensions cannot extend beyond the rear wall of the original house by more than four metres if it is a detached house, or more than three metres for any other house (terraced or semi-detached).

Height: Single-storey rear extensions cannot exceed four metres in height.

4.3. Side kitchen extension

All the above points relating to rear kitchen room extensions would apply, apart from the last two relating to depth and height.

In addition, a side kitchen extension would need to meet the following criteria:

Overall Height: Cannot exceed four metres in height and can only be a single storey.

Width: Can only be up to half the width of the original house.

4.4. Wrap around kitchen extension

Wrap around kitchen room extensions are a little trickier as they do not fall within Permitted Development. This means that wrap around extensions require planning permission.

However, there are quite a few advantages when applying for planning permission over Permitted Development.

Depth: When it comes to Permitted Development legislation, there are specific depths you cannot exceed, whereas there is more flexibility in the acceptable depth of extensions when it comes to planning policies.

Most Local Planning Authorities will have a document online (which can be googled) called ‘Residential Design Guidance’. The reason why these are ‘guidance’ documents rather than ‘policy’ documents is because there is a certain degree of flexibility and more room for interpretation. Sometimes, planners will allow slightly deeper kitchen room extensions which can help achieve that little bit more space.

Height: Similar to the depths mentioned above, Permitted Development has specific legislation relating to the acceptable height of kitchen extensions. When applying for planning permission however, the rules are less rigid and more flexible. This allows you to work with planning officers during a pre-application to play with various heights and be more creative with the final design.

Design: The main advantage of applying for Planning Permission rather than Permitted Development is that there is far more scope to be creative in terms of design. Permitted development has more restrictions, thus limiting the final design.

Planners often like designs which are unique, so the planning permission route certainly gives you more scope to be creative.

Materials: When it comes to Permitted Development, the main caveat is that materials should match those of the main house, but what if you want something a little more modern, like zinc cladding or a dark brick to create something truly unique?

This is where applying for planning permission is advantageous because you can work with a bigger palette of materials.

5. Are there different types of kitchen design?

5.1 One Wall Kitchen Layout

Picture of a modern one wall kitchen design
Modern One Wall Kitchen Design

This type of design is best for homes with limited space or those which are a little narrow. The use of vertical space is very important. The advantage of this design is that everything is within easy reach. The use of shelves and overhead cabinets can maximise space and helps your kitchen become more organised. A new trend is to have a mobile kitchen island on wheels to give that little extra space for storage or a useful place to serve your guests.

5.2. Galley Kitchen Layout

Picture of a Galley Kitchen Design
Galley Kitchen Design

Galley kitchens are fantastic for smaller spaces and great when you have two walls facing one another. We always think it’s a great idea to separate both sides with different uses. For example, one side can be used for storage, fridges and ovens, while the other side can be made more open with a longer work surface making it easier to prepare meals.

5.3. L-shaped kitchen Layout

Picture of an L-shaped Kitchen Design
L-shaped Kitchen Design

These types of kitchen are both streamlined and dynamic. They work well with medium sized kitchens where either an island or dining table is incorporated into the kitchen design. The increased size of the work surface due to the L-shape also gives a far larger preparation area compared to the two options above.

5.4. U shaped Kitchen

Picture of a modern U-shaped kitchen
U-shaped Kitchen Design

These kitchens work well when you have a separate kitchen and dining room. Having the kitchen set around 3 walls really maximises space. This design means there is a lot of work surface space and storage which helps organise your kitchen more efficiently when preparing for those tasty dinner parties. Some U-shaped kitchens can feel a little enclosed and to solve that, we find that open shelving rather than wall units help create a real sense of space.

5.5. Kitchen Island Layout

Picture of a Kitchen Island Design
Kitchen Island Design

These are best suited for larger kitchens and are fantastic spaces to socialise and entertain. They also create a huge amount of space to cater for larger occasions. Part of your island can also serve as a breakfast bar so guests or family can talk to you while you cook.

6. FAQ

6.1. How can I get more light into my kitchen?

There are two main ways to get that little bit of extra light into your kitchen extension.

Roof Light

Picture of a modern Roof Light Kitchen Extension
Large Roof Light in a Kitchen Extension

These are essentially windows in your ceiling. There are a huge number of designs and materials to choose from. Bear in mind that many manufacturers will have off the shelf sizes which tend to be lower in price. If you would like something more bespoke and larger in size, these designs are made to measure but cost a little more.

Bi fold doors

Picture of a BiFold Door Kitchen Extension
Modern Bi-fold Door Kitchen Extension

Not only can bifold doors help bring in a huge amount of light flooding your kitchen, but during warmer weather you can open the doors which brings your outdoor area in, increasing the size of your living area.

6.2. Do I need an architect for a kitchen extension?

The answer to this depends on the scale of your project.

Replacing a kitchen: If you’re replacing an existing kitchen then you could approach a kitchen manufacturer who usually have a team of in-house designers to help you plan the perfect kitchen. You will be able to pick the design, materials, handles, fixtures and fittings to help you create a truly bespoke and unique space.

If your new kitchen will form part of a larger extension, we would always suggest calling an architect first, who will be best placed to help develop your ideas.

6.3. What building regulations approval will I need for a kitchen extension?

If you plan on replacing an existing kitchen with a new one, you will not need building regulations approval.

However, if your new kitchen will form part of a larger extension project, you would require Building Regulations approval.

Do I need a contingency fund for my kitchen room extension?

The short answer is yes.

Extensions are complex structures and there will always be unforeseen costs as your project takes shape.

Our architects would recommend that you keep 10% of your total budget for your kitchen home extension back for emergencies.


The Adara team is made up of a mixture of creative architects and planning consultants. We have a huge amount of experience when it comes to designing stunning kitchen extensions that could transform your home.

If you have any questions or need some advice about your ideas, please feel free to arrange a free 30 min consultation with one of our team here.

We’re always here to help.

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