Planning guide · England & Wales
Two-storey (double-storey) extensions can sometimes be built under permitted development, but the rules are much stricter than single-storey — and many will need a full planning application. Here is how it works in England and Wales, and how we get yours drawn and approved at a fixed price.
Sometimes you can avoid it — a two-storey rear extension can be permitted development within tight limits. But because two-storey work affects neighbours’ light and privacy, the conditions are strict and many projects end up needing a full application.
You will need full planning permission if the extension is to the side (two-storey side extensions are not permitted development), deeper than 3 metres, closer than 7 metres to the rear boundary, higher than the existing ridge, on designated land, or on a flat. There is also no 6m/8m larger-extension scheme for two-storey work — that only applies to single-storey rear extensions.
Two-storey extensions face the strictest permitted-development conditions. Here is how each nation treats two-storey rear extensions.
We are an online architectural design service — the practical alternative to a traditional high-street architect. Our qualified design team draws your plans, works out whether you are permitted development or need a full application, and deals with the council on your behalf.
Often, yes. A two-storey rear extension can be permitted development within strict limits (max 3 metres deep, at least 7 metres from the rear boundary, no higher than the existing ridge), but two-storey side extensions, larger projects, designated land and short gardens all push you into a full planning application.
Up to 3 metres beyond the original rear wall, and it must be at least 7 metres from the rear boundary at its closest point. If your garden is short, you likely cannot build a two-storey extension under permitted development.
No. Two-storey side extensions are not permitted development and require a full planning application in both England and Wales.
No. The Larger Home Extension prior-approval scheme (6 metres for semi/terraced, 8 metres for detached) applies only to single-storey rear extensions. Two-storey extensions are capped at 3 metres under permitted development.
Yes. A two-storey extension needs building regulations approval covering structure, foundations, insulation, drainage, fire safety and more — in addition to planning permission or prior approval.
With Arkiplan, drawings are typically ready in three to six weeks after your design call. A full planning decision usually takes around eight weeks from a valid submission, though this varies by council.
No call required, no card required — just a tight, fixed-price range tailored to your project, with the planning route confirmed for your address.
This guide is general information, not planning advice, and permitted development rules change and depend on your specific property and local authority. We confirm the current position for your address as part of every project.