How to add an extra two floors without requiring planning permission

Posted by Derek Mason

13th April 2021

Adding two extra floors to your property used to require planning consent. So the removal of that need when you’re adding two storeys to a residential property has created a real growth area for our industry.

The government changed the rules last year, as part of its bid to increase available housing. So adding two storeys (up to 18m) to a property is now within permitted development rules. There are pros and cons to this change and, of course, it has its fans and its detractors.

On the one hand, it removes a layer of bureaucracy and means that it will be much more straightforward to add two additional floors to flats, apartment buildings and houses. And of course it may lead to more creative designs – which could be a bad thing or a good thing, depending on the designs and the locations involved.

On the other hand, there’s a risk that neighbours will fall out with each other over designs that encroach on or overshadow existing homes, or simply look ugly. Another possible downside is that undersized homes could end up being built.

But on the face of it, this is largely a good idea, as long as everyone involved behaves responsibly. In fact, we’re advising on a project right now to add two additional floors to a block of flats. Support is a key factor in these kinds of extensions, and with this project we’ll be using an external skeleton frame to support the extra floors and this will be clad to hide the external frame, as shown in the picture below.

It seems likely that this kind of project will become more and more common, as people wake up to the potential for adding extra floors to existing homes.

However, there is one restriction that is going to limit this type of development, and that’s the age constraints. If the property was built before 1 July 1948 or after 5 March 2018 you can’t extend two floors into the sky without planning permission. (Those are the dates for adding new flats – it’s after 28 October 2018 for extending an existing home.)

If you’re in a conservation area, national park or other protected area, or your home is a listed building, you can’t take advantage of these new rules either. And if you’ve already extended upwards, that rules you out.

It will be interesting to see how this trend unfolds. We could end up seeing some interesting, creative designs that make a positive addition to our housing stock. Or we could see people playing it safe and creating functional designs for their rooftop extensions.

As a structural engineer, one of my main concerns is that people are tackling these projects in a way that’s safe. It should go without saying that the existing building needs to be able to support the additional floors.

What do you think? Is this a questionable idea from our government, or a positive one that’ll help us to increase the numbers of homes available in the UK? Reply and let me know.

And if you’re working on a similar project or extension, and you need assistance with the structural elements, please do get in touch.

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