Single Or Double-Storey Extension: Which Should I Choose?


Whether you need more space, or simply want to develop the home that you love, building an extension might well be next on your to-do list. With so many people choosing to stay put and improve the house they live in, rather than move, it’s clear to see why building an extension is becoming a more common option. However, the next question you’re probably asking yourself is: do I go for single or double-storey? With plenty of benefits to both, the team at Keenan Project Designs have put together this handy guide to help you decide.


Ultimately, the reason you’ve gone down the extension route in the first place is to create additional space and both single and double-storey options promise to do just that. However, a single storey extension consists of additional ground space only and can be used to create extra or enhance current living space, dining space, or a playroom, for example.

A two-storey extension, on the other hand, will not only provide extra room downstairs but upstairs too. If you have a growing family, you might feel you want to invest in a two-storey extension to prepare for the future, as an alternative to moving to a new house.


Let’s be honest, price is probably one of, if not, the biggest factors to consider when you’re developing your home. It will come as no surprise that a single-storey extension is the cheaper option.

On average, the price for a 30 square metre storey extension costs between £30,000 to £48,0001. In comparison, the cost for a two-storey extension ranges between £48,000 and £76,0001. Those who have a bigger budget to play with can look at spending anything around £60,0001 on a single-storey extension.

Remember, builders generally quote for cost per square metre, rather than the number of storeys, so a double-storey extension is arguably a more cost-effective option. After all, you’re getting more space for your pound if you go for the double, it just depends on whether your budget can stretch that far.

Of course, where you live plays a huge factor when it comes to cost. Remember, if your location is near to, or in, London or the South East of England, then expect to pay more.


As with price, it’s no shock that a two-storey extension takes longer than a single. With a single taking, on average, around 12 weeks and a double, nearer 16 weeks, depending on the size and complexity of each job.

Planning Permission

Depending on whether you’re opting for a single or two-storey development, you may need to get planning permission for your extension. Have a read of our blog on planning permission to find out more and discover when this isn’t required.

When building a single-storey extension, it’s likely to only impact the homeowner, however, you must consider your neighbours if you’re going for the double. Although this issue will be tackled when you apply for planning permission, it’s best to reduce any potential stress, anxiety and disagreement, by speaking to your neighbours ahead of any final decision making.

Whether you’re heading down the single or double-storey route, it’s definitely wise to speak to the experts at Keenan Project Designs, to make sure you’re maximising potential when it comes to your extension, so you’re getting the most out of your new space while ensuring your development is cost and time-effective.

Contact us and we’ll be happy to advise you further. Not only are we a RIBA Chartered Practice, but we also offer a company ethos of being reliable and trustworthy, with a focus on quality. Our services span Warwickshire and beyond, including Rugby, Coventry, Leamington Spa, Kenilworth, Northampton and Solihull.

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