Garden room in Wandsworth

Often no application is needed — under Class E permitted development, a garden room used for a purpose incidental to the house (office, gym, studio) qualifies without planning permission provided it stays under 2.5m high within 2m of any boundary, covers less than half the garden together with any other outbuildings, and stays behind the principal elevation of the house. This applies across most of Wandsworth, including at the rear of properties within its conservation areas — only a listed building loses the right entirely, and sleeping accommodation always needs a full application.

Common across the borough's terrace gardens; the 2.5m boundary-height rule is the most-breached limit.

Wandsworth's stock is overwhelmingly Victorian terraces, where the 50% coverage rule — measured against every outbuilding and extension on the plot together, not just the new room — tends to bind before the height rule does, especially once a rear extension has already used some of the garden. Garden rooms are common across the borough, including inside its conservation areas: Class E still covers a rear-garden building there, but the same right doesn't extend to outbuildings sited at the side, which is worth knowing before you plan the layout.

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.