How much will my kitchen extension cost?

side return extension
Side extension Nunhead (during)

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We get asked often how much a kitchen extension will cost? Well, safe to say that there are a few things that can be considered which will enable you to adequately price your project costs. Firstly, I should say that the pricing team here provide all inclusive quotes. Everything  required to build what you want from the information provided to us, will be accounted for. Then, outside of this, we will let you know what is to be provided by yourself.

There are some predetermined, design and project specific costs for different types of work that allows us to accurately price a construction job. Each project is of course estimated on it’s own merits

What things affect cost of kitchen extensions in London?

So what sort of of things will help answer the question of cost? The existing and proposed space, layout, design and structure, internal remodelling, external appearance and internal fixtures and fittings, are to be considered. There will be standard considerations in all types of kitchen extensions, as well as unique attributes to your job.

Let’s work through an exercise together. Say the base price for a five metre long and two meter wide side return extension is around forty thousand pounds excluding VAT. Please note this is not a guide price, it’s just our starting point to costing a working example through choices you might make.

If you are considering a side return extension (or indeed a single storey rear kitchen extension) for instance, what type of doors do you have in mind? French doors, with or without side panels? Sliding doors? Aluminium or timber bifold doors?

Door sizes and related structure…

Full width doors at the rear of your kitchen extension, or slightly less than full width with wall nibs on either side of about half a meter? Anything that is full width will require a ground beam, supporting two columns and the beam above the kitchen extension doorway opening.

In the single storey side return kitchen extension in the photos above (all the photos from the same project) the client went for full width white timber bifold doors. The immediate gallery above shows the additional steel structure required (ground beam and two columns for this kitchen extension). In most situations going full width would in total add another three thousand pounds to construction costs labour and materials, and an additional five hundred pounds or so to bifold doors for example.

In addition to this, if the doors have to be ordered bespoke for the opening (which they might), that would add another one thousand pounds to the cost of the doors themselves. That said, if one of the door supplier standard sizes closely fits your doorway opening width and height, you could save money by ordering that and adjusting the opening brick or block work.

In total then the width of the doors you choose could mean a plus or minus four thousand five hundred pounds. Our base price has moved from £40,000 to £44,500.

Your kitchen Extension external finishes?

Would you like the extension to be in keeping with the existing external appearance of the property? There will be a choice usually between a painted render finish or facing brickwork. Facing brickwork is more expensive than rendered over blockwork in most cases. London Stock bricks are usually £1.80 plus VAT a brick. That said, if your structural engineer has specified a certain type of block because kitchen units will be hung along the length of wall, then cheaper blocks won’t be an option. Typically, a brick finish can add between two and three thousand pounds in materials and labour (dependant on the wall sizes).

Our price can now be adjusted from £44,500 to £47,500 because we have chosen external facing brickwork (in this example)

Skylights, rooflights, Velux, Fakro…

Glazing is next for our consideration in our kitchen extension – do you want them included in your quote, or want to supply them yourself and we fit them for you? The cost should be the same, it’s should be a matter of which side they appear on the costing sheet. As in doors, standard and bespoke sizes will make a considerable difference in price if you are having fixed rooflights. The lead times of bespoke rooflights too will be two to three weeks longer than standard sizes (this applies to doors as well as windows). In any case, whether you purchase the windows yourself or ask your builder to, the sum is the same. Ok, so you opt for three rooflights on the the side extension pitched roof – we move from £47,500 to £49,500.

Inside your kitchen extension

What other considerations should we be thinking about for our side return extension example? Internally, things like underfloor heating, feature lights, tiling area and tile size, coving material, skirting, decorating and internal fixture and fittings can affect price. Now, none of this might change what you have long since settled on, but let’s say your maximum budget was around £50k excluding VAT, then you could make choices in some areas.

Underfloor heating

In our working kitchen extensions example, underfloor heating could add another £3,000 (for a good kit, pipes, manifold, high flow for extensions), to the job, so we move from £49,500 to £52,500. Then is the existing boiler recently changed, or has that been there a while and will need to be changed? Where we install combination boilers we advise to use one of two leading manufacturers. Add another £1,500 including fitting the boiler (boiler budget in this example £1,100). Now at £54,000 excluding VAT.


Tiling in your kitchen extension. The size of your tiles generally will not make a difference as this is prices per metre square, unless your tiles are say 1.2m by 60cm. Also, will you want to run tiles outside for a patio area leading to the garden? If this is a decision made after the project has started, the cost of the external tiles and labour could be an additional spend of circa £3,000; total £57,000 excluding VAT.


Coving, if required in a kitchen extension project – is this going to be high end, or made out of gypsum? Or something at the other end of the spectrum that you can pick up from a local building store?


We use one brand of white paint for undercoat and two top coats of Dulux Pure Brilliant White quite a lot. In fact we account for all white paint in our quotes. If you want some feature walls, or like other paints like Farrow & Ball, you would have consider this in the overall budget.

Scope of works

In some kitchen extension projects the scope of works are amanened and added to as they go along. Here, at Planning & Build, we work with clients to consider all requirements at the start and account for them. For this reason, once we do give a quote, they don’t change. And if you do receive a quote from us and are comparing it with another quote, please look through it carefully to see what what is included and what is not (like for like). If we are doing the architecture and structural drawings for you as well, that price will be in the quote too.

In summary

If you had in mind a budget of £50k plus VAT for your kitchen extension, then you could keep within this budget. Don’t forget that you might also have to purchase things on the client side – kitchens, appliances, tiles, feature lighting, and furniture for example. We hope this helps, do get in touch if you want us to provide you with your kitchen extension quote.

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We have a track record for customer satisfaction in the entire process from design through to build. Equally as important for us however, is that we strive to produce exceptional quality work at competitive prices. Get in touch today to discuss your project.