Once you’ve made the decision that it makes more sense to build an extension onto your existing property than move home altogether, the next step is to find out exactly how much this is going to cost.
And that’s why, in this article, we have researched the various types of extension you can consider for your home, and how much you can expect to pay for each.
How To Recoup The Cost Of Your Home Extension
On the whole, an extension will add value to your home. However, it’s still worth checking, before you give the builder the go-ahead, what other homes in your locality with a similar extension are selling for.
That’s because there’s no point splashing out on a huge house extension if you’re not going to recoup the costs when it comes to selling up and moving on. Unless, of course, you’re not planning on moving for a decade or so anyway and just want to make your family home – and the house you love - that bit bigger.
Location, Location, Location
Of course, the overall cost of your extension will also depend on other factors, such as where you – and who you get to do it – live. An architectural designer with plush offices in London’s West End will cost more than a one-man operation working from home in the Peak District, for instance.
One London designer recently quoted around £150 per square foot for a ground floor extension (which took into account the fixtures and fittings too). It didn’t, however, include other costs such as architect, construction, planning and building control fees. Another designer quoted £250 per sq ft for a basement extension which created a whole new living space under the existing house.
There is also the matter of the condition of your existing property, as well as its age, and the materials used in its construction. On the whole though, it’s possible to calculate basic average costs for particular types of extensions. We’ve listed the main ones here:
Single Storey Extension
A typical single storey extension added on to your property – usually at the back of the house – can create a completely new ‘open plan’ living space for the family. Both the kitchen and lounge area can sit side by side, and there is usually easy access to the garden area. Costs (for an average 4m x 5m extension): £32,000.
Double Storey Extension
To get more or less the same shape and size as the single storey, this time on two floors, you’re obviously talking about double the time and fees when it comes to construction costs. Yes, it’s more expensive than the single storey but just think what you can do with all that lovely new space! Costs (for an average 4m x 5m extension): £48,000.
More expensive than a single or double storey extension, the basement conversion involves lots of extensive ground work. The cost can also depend on whether there is an existing cellar there or if you’re starting from scratch and having to underpin the walls. Costs (for converting an existing cellar): £450-650 per m² (for having to build from scratch): £2000 to £4000 per m2
There are various types of attic conversions, depending on how adventurous and generous with space that you want to be. There’s also the question of whether you’ll get planning permission or even if there’s enough room for the type of extension you’d like. Basically the selection boils down to four:
This is the simplest option and because of that, also the least expensive. It’s merely a matter of adding one or two windows to the roof to make the space lighter. Costs: £15,000-£25,000.
The most popular type of attic conversion here in the UK - you’ve probably a number in your street right now – the dormer has a small flat roof and a couple of windows. You can even have side and rear extensions to the dormer. Costs: from £25,000-£30,000 for a standard Dormer and £30,000-£35,000 for an L-shaped Dormer.
• Hip to Gable
A large extension, which involves replacing one or both of the end sloping parts of the roof with a gable wall. Costs: £30,000-£40,000.
The largest and most major attic extension, the Mansard involves replacing entire roof so that it becomes a twin pitch roof. In some cases it can mean getting a whole new storey built. This will require planning permission. Costs: £45,000-£50,000.
Single Room Extension
A single room extension can be built on to the side of the house. More commonly these take the form of bathroom or kitchen extensions. Obviously plumbing fees are going to play a major part in the overall cost here – both for the bathroom and kitchen. Fees will also be influenced by your design tastes i.e. whether you’re aiming for high-spec fixtures and fittings or basement bargains. Costs: £15,000 to £25,000
Always Get Several Quotes
Another way of understanding how much your new extension will cost is to get several quotes from architectural designers and construction companies. Bear in mind though these are estimates and not the final cost, which may go up quite a bit by the time the final bill arrives. Incidentally this is why, regardless of the cost you’re quoted, it’s a good idea to put aside an additional 10 per cent as a contingency fund.
Meanwhile, having a separate architectural designer and construction company doesn’t always make the build go smoothly and which is why it makes sense to find a company – such as BDS Architecture – which can do both. It’s also less confusing when it comes to working out the fees since you’ll only receive the one quote for all the work together.
You can find out more about the process of having an extension built for your home by downloading our free eBook, entitled The Ultimate Guide To Expanding Your Living Space. It’s a good starting point and should answer at least some questions if you’re unfamiliar with the terminology and planning process of having an extension built to your home. For any additional information, please don’t hesitate to give one of our designers a call.