Often not — and that surprises people, because a conservatory feels like a big enough change to need someone's blessing. In planning terms it is treated as an extension, and most modest ones fall under permitted development, which means you can build without applying. The catch is that "most" is doing a lot of work in that sentence.
What permitted development actually allows
For a single-storey rear conservatory on a house in England, the headline limits are these. It cannot extend more than three metres beyond the original rear wall on a terraced or semi-detached house, or four metres on a detached one. It cannot be more than four metres high. If it sits within two metres of a boundary, the eaves cannot exceed three metres. And together with everything else you have built, it cannot cover more than half the land around the original house.
"Original house" means as it stood in 1948, or as first built if later. If a previous owner already added a rear extension, their allowance has been spent and it counts against yours. This is the single most common way a conservatory that looked fine on paper turns out not to be.
When you definitely do need permission
- You are going beyond those size limits — though a larger rear extension may still be possible under the prior approval route, which is a lighter-touch application rather than a full one
- The property is a flat or maisonette — permitted development for extensions does not apply
- It is a listed building, where you will also need listed building consent
- You are in a conservation area, an AONB or a national park and the conservatory is to the side
- Your permitted development rights have been removed by condition — common on newer estates, and easy to miss
That last one catches people out more than any other. A planning condition on the original estate approval can strip permitted development rights from every house on it, and nothing about your deeds will announce this cheerfully. It is worth checking before you order glass.
Permitted development is not the same as proof
Here is the part that costs people money years later. If your conservatory is permitted development, you can build it without asking. But nobody has written anything down confirming that, and when you come to sell, a buyer's solicitor will ask what authorises it. "It didn't need permission" is a claim, not a document.
A Lawful Development Certificate closes that gap. It is a formal confirmation from the council that the work was lawful, and it is the thing a conveyancer actually wants to see. Our PD Compliance Pack assesses eligibility first and then produces the drawings and application for one.
What the drawings need to show
Whichever route you take, the drawing set is much the same: a location plan, a site plan, and your house drawn both as it is now and as you propose it to be, in plan and elevation. The council is checking the proposal against the limits above, so the existing drawings matter as much as the proposed ones — they establish what the original house was.
Our Standard Planning Pack covers a full householder application at a fixed £650, and the extension drawings page goes through what is included in more detail. Both routes are the same fixed fee, because they are the same drawing set.
Building regulations apply either way
Planning permission and building regulations are two different things, and it is worth being clear that avoiding one does not avoid the other. Conservatories have historically been exempt from building regulations where they are separated from the house by external-quality doors, are largely glazed, and have an independent heating system with its own controls. Knock through into the kitchen and remove the doors, and that exemption goes with them.
The short version
A modest rear conservatory on a house, within the size limits, with permitted development rights intact, does not need planning permission — but does deserve a certificate proving it. Anything larger, on a flat, on a listed building, or where rights have been removed, needs an application.
If you are not sure which of those describes you, that is the normal starting point rather than an admission of anything. Send us the details or ring 0114 463 0090 and we will tell you which route you are on before you commit to either.