Class E
Garden rooms and outbuildings: what you can build without permission
Anatolie Chiriac · Graduate Architectural Technologist
Last reviewed August 2026. Relates to England. General guidance, not advice on a specific property.
Garden offices, gyms and studios are usually permitted development under Class E. The dimensional limits are straightforward. The test that actually decides most disputed cases is not dimensional at all.
The dimensional limits
- Maximum height 2.5m if any part sits within 2m of a boundary.
- Otherwise, 4m for a dual-pitched roof or 3m for any other roof.
- Maximum eaves height of 2.5m.
- Single storey only.
- Together with extensions, no more than half the land around the original house may be covered.
- Nothing forward of the principal elevation.
- No verandas, balconies or raised platforms.
The test that catches people: ‘incidental’
Class E permits buildings required for a purpose incidental to the enjoyment of the dwellinghouse. Incidental means subordinate — a use that supports the household rather than forming part of the main living accommodation. A home office, gym, workshop or store is normally fine. A self-contained annexe with a bedroom, kitchen and bathroom generally is not, because it is primary living accommodation rather than something incidental to it.
Size feeds into this test but does not settle it. Appeal inspectors have refused certificates for outbuildings that met every dimensional limit, on the basis that no evidence was given for why a building of that size was genuinely and reasonably required for the stated incidental purpose. Case law requires an element of objective reasonableness — it is not purely for the occupier to decide.
Practical consequences
If you intend to run a business from the building, receive customers, or accommodate a relative permanently, the incidental test is where the scheme will be judged — not the height. Being able to explain and evidence the intended use matters as much as the dimensions.
Where the rights don’t apply
Flats have no permitted development rights. On Article 2(3) land, outbuildings to the side of a house are excluded and buildings more than 20m from the house are limited to 10 square metres. Article 4 directions and listed building status remove or restrict rights entirely.
General guidance on the position in England, not advice on a specific property.
Whether these rules let you build what you have in mind depends on measured dimensions and your property’s planning history — neither of which can be settled from an article. If you want a view on your own house, send us the details.
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