Most kitchen extensions go on the rear of the house, and for a lot of properties, there’s a genuinely fast route to a decent amount of space: prior approval. But one specific feature of a house catches people out more than almost anything else — a staggered rear elevation. If your house has one, prior approval is off the table entirely, no matter how straightforward the rest of your project looks.
The routes available under permitted development
Under a lawful development certificate, typical depth limits are 3 metres for semi-detached and terraced houses, and 4 metres for detached houses. Beyond that, there’s the prior approval route — the “larger home extension” process — which is genuinely one of the fastest ways to get a significant amount of space: an eight-week, 42-day process that can get you a rear extension of 6 to 8 metres, depending on house type.
That’s a lot of space, quickly. But it depends on one thing that a lot of homeowners don’t think to check.
Why a staggered rear elevation rules it out
Both permitted development and prior approval require the extension to attach onto a completely flat rear elevation. If your house has a staggered rear — meaning it isn’t flat across the back, often because of an original single-storey element such as a small original extension — you can’t apply under either a lawful development certificate or prior approval.
This catches people out because it applies even if that original single-storey element has since been demolished. What matters is the original construction of the house, not what’s currently standing — if the house was originally built with that staggered element, it’s still assessed as staggered, however it looks today.
What happens instead
If your rear elevation is staggered, the project moves to a household planning application, and instead of the national permitted development figures, you’re subject to whatever depth limit your local council applies — and that varies significantly from council to council, even for the same house type.
As an example: on the same style of semi-detached house, one council might allow 3 metres, a neighbouring one 4 metres, and another 3.5 metres. Three councils, the same type of house, three different answers — which is exactly why checking your specific council’s rules matters before you assume prior approval will work for you.
The takeaway
Before you assume your kitchen extension qualifies for the fast prior approval route, check whether your rear elevation is genuinely flat — including its original construction, not just its current shape. If it isn’t, you’re not stuck, but you are working to your council’s specific limits rather than the national permitted development figures.
You may also like to read: Kitchen Extension Design for Semis: Layout Option & Wraparound Extension: Why You Can’t Do It Under Permitted Development
