Garden room in London

A garden room is a detached outbuilding — home office, studio, gym — at the rear of the garden. Since 2020 it has become London's fastest-growing project type, and for good reason: under permitted development rules many garden rooms need no planning application at all.

Quality spans flat-pack pods to architect-designed garden studios. The planning rules are generous but precise, and the commonest mistakes — height over the limit at the boundary, sleeping accommodation, taking too much of the garden — are all avoidable with a constraint check first.

The planning route — PD or permission?

Permitted development (GPDO Class E) allows outbuildings for purposes incidental to the house: maximum 2.5m height within 2m of a boundary (4m for dual-pitched roofs further in), no more than half the garden covered, nothing forward of the principal elevation, and no sleeping accommodation. Within conservation areas Class E still applies at the rear, but outbuildings at the side are excluded.

The 'incidental use' test matters: an office or gym qualifies; a self-contained annexe or rentable unit does not and needs full permission. Listed buildings lose Class E entirely — any outbuilding in the curtilage of a listed house needs an application. Where you intend to run a business with visitors or convert to sleeping space later, take the planning route up front.