The permitted development rules for garden rooms and outbuildings
An outbuilding is permitted development on a house if it is single storey, no higher than 2.5 m where it comes within 2 m of a boundary, otherwise no higher than 4 m with a dual-pitched roof or 3 m with any other roof, sits behind the front wall of the house, covers together with other outbuildings no more than half the land around the original house, and is used for purposes incidental to the house rather than as a bedroom or self-contained flat.
Anything used for sleeping or as a separate dwelling needs planning permission regardless of size. Flats have no permitted development rights for outbuildings, and listed buildings need listed building consent.
What changes in Greenwich
In a conservation area an outbuilding is still permitted development behind the house, but not to the side of it, and the same height limits apply.
The local constraints that most often decide the route in Greenwich are listed below, taken from our Greenwich area page. Each one is a reason to confirm the address on Greenwich's constraints map before relying on permitted development.
- Conservation areas. Royal Greenwich has numerous conservation areas, including West Greenwich, Blackheath, Blackheath Park, Westcombe Park, Charlton Village, Eltham Palace, the Progress Estate and Woolwich Common. Roof extensions are not permitted development inside them and extensions are expected to be subordinate and in matching materials. Source
- Article 4 directions. Several conservation areas, notably the Progress Estate in Eltham and parts of Blackheath, have Article 4 directions removing permitted development for external alterations, so most changes need planning permission. The exact scope varies by area; check the council's constraints map for your street. Source
- Thames flood risk. The riverside from Greenwich Peninsula through Charlton, Woolwich and Thamesmead lies in Flood Zones 2 and 3 behind the Thames Barrier and river defences. Ground-floor extensions and basements there may need a flood risk assessment. Source
- Metropolitan Open Land and Royal Parks. Blackheath, Greenwich Park, Woolwich Common, Oxleas Wood and Shooters Hill are Metropolitan Open Land or Royal Park. Plots on their edge face closer scrutiny for outbuildings and for anything visible from the open space. Source
- Listed buildings. Greenwich town centre, Blackheath and Eltham contain a high concentration of listed buildings. Listed building consent is needed for almost any alteration, internal or external, alongside planning permission. Source
What Greenwich planning officers look for
Royal Greenwich officers are heritage-conscious in the west of the borough and more relaxed in Eltham, Plumstead and Kidbrooke. Common refusal reasons are rear extensions that breach the 45-degree line or exceed the neighbour's depth, roof extensions in conservation areas that break the roofline of a terrace, front dormers, and alterations to Span houses or the Progress Estate that depart from the original detailing. The council offers a paid pre-application service, which we recommend in the World Heritage Site buffer zone and Blackheath. Decisions often run past 8 weeks; allow 10–14 weeks.
Fees and timelines
The council fee for a householder application is £528 and for a Lawful Development Certificate £264 (England, from 1 April 2025; verify before applying). Both are decided within 8 weeks of validation.
Our own fee for the drawings and the application is fixed once quoted and depends on the project type, its size and the constraints above. Answer six questions in the quote tool and we email you an indicative figure within minutes, then a written fixed-fee quote within 24 hours.
