Can I build an extension without planning permission?

In many cases, yes! But there are some important rules (and a few exceptions) to be aware of.

As one of those questions that pops up early in almost every project: Do we need planning permission for this? Or can we just go ahead and build? The good news is, in lots of cases, the answer is: you might not need it at all.

Thanks to the UK’s Permitted Development (PD) rights, certain types of home extensions and alterations can go ahead without the need to submit a full planning application. That means fewer hoops to jump through, less red tape, and often, a much quicker start to your build.

But, before we get ahead of ourselves, it’s important to know that Permitted Development doesn’t apply to every situation. There are specific rules and limits, so it’s always wise to check with your local authority or a professional before making any assumptions.

Here’s a general idea of how it works. Under PD, you can often extend your home at the rear (single-storey and sometimes double), convert lofts, and even add outbuildings as long as you stay within the size, height, and placement limits set out in the legislation. For example, a single-storey rear extension can usually stretch out by up to 3 metres on a terraced or semi-detached home (or 4 metres if detached), and must not take up more than half the garden. It can’t be taller than 4 metres, and materials should be in keeping with the existing house.

Loft conversions also fall under PD in many cases - up to 40 cubic metres for terraced houses and 50 for detached and semis, again with height and roofline restrictions. And don’t forget, if your home is in a Conservation Area, Green Belt, AONB, or is a listed building, different rules apply and PD may be restricted or removed altogether.

Another thing to be aware of is something called a Lawful Development Certificate. Even if you don’t need planning permission, it's a smart move to apply for this certificate. It’s official confirmation from your council that your proposed work is within the permitted rules. It can be really useful if you ever come to sell your home and need to show buyers (or their solicitors) that everything was above board.

In my work, I often help clients assess whether their ideas fall within PD or whether a tweak to the design might bring it in line. Sometimes a small compromise can mean avoiding a lengthy planning process altogether. And even if you do end up needing planning permission, understanding your rights and starting with a strong design can make the whole process much more straightforward.

It’s worth saying that while Permitted Development offers real flexibility, the rules can be a bit fiddly and they do vary slightly by region. So if you’re in doubt, or right on the edge of what’s allowed, check with your local planning authority or speak to someone who’s used to navigating this stuff (Hi!).