How Much Does a Kitchen Extension Cost?

It’s a tough cookie to crumble this one, but we’re going to try. So you want to know how much it costs to get one of these lovely big kitchen extensions in a terrace street in London? Preferably on a Victorian semi I’m guessing? Well read on…

First just a quick caveat, these figures are our estimates at the time of publishing, Brexit and Covid have affected costs, it started with wood and concrete and then moves to plaster board, labour, and pretty much everything else it takes to create an extension.  Also, all prices mentioned are London centric, things may well be differ elsewhere!

For this rough estimate though, we’re going to assume you have middling taste in finishes a mixture of a few higher end items like marble and more of a standard engineered wood flooring for example. Kitchens and bathrooms elevate themselves entirely with the odd splurge of luxury finish, that slab of stone will pull up your Ca' Pietra tiles by their boot straps!  A few Vinterior and Auction finds thrown in for good measure will bring the character. To keep it simple, we’ll also assume that your extension is going to be 3 meters which, unless you are in a conservation area will mean it falls under permitted development and therefore no planning is needed (these rules do change so always check in your given area).

To start with, you’ll want your building plans, structural calculations and to instruct a building regulations company. We suggest going through a private company for this rather than the council who tend to be a bit slow when it comes to visits. You’ll need any relevant water permissions and a party wall agreement unless you are detached and surrounded on all sides by a little bit of land, a luxury most terraced houses don’t have… This ‘paperwork’ as we call it is going to come in at around £5-9K mostly dependent on your chosen architect.

It’s at this time you’ll also want to factor in your Interior Design – you may think this is early but it makes total sense to start now. Interior designers can work with your architect to ensure that your final design and living space is every inch perfection. How will those wall sconces go in if there’s no wiring ready for them? How will you know where to put plug sockets if you don’t know what furniture and lighting plans you’re going with? What finishes will you be using? And so on…

Then we get to work! You’re looking at about 3-5 months for a kitchen extension and ground floor remodel, in labour fees that means you’ll probably find yourself somewhere in the region of £70-85K. This should include building materials but always check with your trade where what they provide starts and ends so you get your figures right. It's also wise to stick an extra 20K somewhere or know that you could get a little loan to the same amount if really necessary, that way you never need to panic or compromise. During this time you’ll need the steels that the structural calculations company have said are necessary. Usually these are to support the original back wall of the house and also to support the new back wall above the back doors. There may be more if for example, you’re removing a chimney breast to make way for flush kitchen units. Steels you can budget for around £4,000 although they may also be included in your builders quote. Should you be doing something very open plan you may want to budget more like £6-9K this is very dependent on the design of your extension, width of open plan space you want to achieve and the positioning of walls you wish to remove. 

Then, once the place is built it needs decking out. By this point you will have made all your major interior design decisions and paint, flooring and bathroom items will be coming into play.

Many people fall into a bit of a trap here when their build is agreed to take them to ‘first fix’ only. First fix is when you get left with plastered walls, ready and waiting to be painted, an empty room waiting for a kitchen, bathrooms to tile, plumbing to attach and doors to be hung. All of which needs fitting, so more labour. This is why a first fix extension seems like such a good option for the bank balance but in the end, often costs more as you add on the necessary extras towards the end, not to mention the possibility of having to find decorators and kitchen fitters to continue the job. Many choose this first fix option with the intention of finishing off a lot of the decorating themselves, which is great if you have the time but often you don’t, leaving you with a room painted here, some tiles laid there, someone called in for this, a balls up with that and often it can end up costing more (certainly taking a lot more time) than if you had got an all in cost (which can seem scary a scary figure at first but often when you break it down, makes sense)… an extension is a big space to paint yourself and be warned, painting fresh plaster needs a good 4 coats! You can probably reliably apportion around £1,000-£1,500 to paint each average size room which would fall into the 3 x 4 meter category.

So with that in mind, we’re going to take this rough price gauge up to the ‘I can actually live in the house now stage’ or, in trade terms ‘2nd Fix’. You’ve got to buy your kitchen, hard to say a price for this as it’s so dependent on tastes, providers and appliances but let’s give it a range of £30-100K, £30 being your Wickes kitchen with some extra drawer inserts and home brand appliances and £50k being your Harvey Jones + £100k being custom.  Then maybe a downstairs loo to go under the stairs? £700-1,000 (assuming the plumbing and creation has already happened). Paint  in a typical F&B or Little Greene approx £500-£700. Flooring, tiles, real wood or a wood effect laminate could range, again dependent on sq meterage anywhere from £4000-£10,000+. Bit of marble or Quartz for your worktop? Budget for about £8-15k dependent on taste for colour and veins.

Back bi-fold doors and roof windows will range from £9-10K if you're sticking to a budget but you can easily sink £20-40K into back doors if you want to. A lovely over Island light fitting or two put by about £800-£1,000.

All in all, if we stick to the middle of these estimates you’re looking at an average cost of around £280,000 with your cheapest option, if you’re really thrifty and your home is on the smaller side, around £190K.

Then you have to start thinking about your furniture…..be sure to save some budget for that too and don't forget rugs and curtains! It’s one of the most fun areas! And, it’s where we really go into our element.

If you’re planning an extension or renovation and want advice or interior design services Treowe offers both in person appointments for advice as well as a Full Service Architectural Design studio. We’d love to chat about your project! Find more details here