Planning Permission Rules for Garden Rooms, Explained

A garden room is a building, not a shed kit, and the planning rules treat it that way. Most fall under permitted development, meaning no application is needed, but the conditions are specific to height, boundary distance and how the space is used, not just overall size.

Height and boundary rules

The height limit depends on both the roof shape and how close the structure sits to a boundary. A dual-pitched roof is allowed up to 4 metres when it's more than 2 metres from any boundary; any other roof shape (including a flat roof) is capped at 3 metres in the same position. Move within 2 metres of a boundary and the limit drops to 2.5 metres regardless of roof shape, which is why a taller garden room usually needs to sit further back from the fence line than people expect.

The 50% rule

Permitted development also caps how much of the garden can be built on in total. A garden room, alongside any existing shed, garage or other outbuilding, can't cover more than 50% of the land around the original house. This catches people who already have a garage or summerhouse and assume the garden room is a separate allowance, it isn't.

What tips it into needing full planning permission

A few things reliably take a garden room outside permitted development, regardless of size: using it as separate, self-contained living accommodation (as opposed to a home office, gym or studio used alongside the main house); adding a veranda, balcony or raised platform, which are excluded from permitted development entirely; building forward of the house's principal elevation facing a road; and, as with extensions, being on a listed building or in a conservation area with tighter restrictions. Any of these means an application is needed even if the structure itself is well within the height and coverage limits above.

We design and build garden rooms to the same structural, insulation and electrical standard as an internal room extension, and check the planning position against your specific plot before quoting, so there are no surprises once foundations are in.