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 Enfield
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 Enfield are listed below, taken from our Enfield area page. Each one is a reason to confirm the address on Enfield's constraints map before relying on permitted development.
- Green Belt. Enfield has one of the largest Green Belt areas of any London borough, covering Crews Hill, Botany Bay, Forty Hill, Whitewebbs, Trent Park and the fringes of Enfield Chase. Extensions to houses in the Green Belt must not be disproportionate to the original dwelling, and outbuildings face a strict test. Source
- Lee Valley flood risk. The eastern edge of the borough along the River Lee and its tributaries (Salmons Brook, Pymmes Brook, Turkey Brook) sits in Flood Zones 2 and 3, affecting parts of Edmonton, Ponders End, Enfield Lock and Brimsdown. Ground-floor extensions there may need a flood risk statement. Source
- Conservation areas. Enfield has numerous conservation areas, including Enfield Town, Forty Hill, Bush Hill Park, Winchmore Hill Green, Southgate Green, the Lakes Estate and Trent Park. Roof extensions are not permitted development inside them and extensions are expected to be subordinate and in matching materials. Source
- Article 4 directions. Several Enfield conservation areas, including Bush Hill Park and the Lakes Estate, have Article 4 directions removing permitted development for front alterations, boundary walls and some roof works. The council may also have a direction on houses in multiple occupation. Check the constraints map before building under PD. Source
What Enfield planning officers look for
Enfield officers are, in our experience, reasonable on suburban householder work but firm on set-backs and the 45-degree test. Common refusal reasons are two-storey side extensions flush with the front wall that create a terracing effect, rear extensions deeper than the neighbour's, front dormers, and box dormers that wrap the hip. Hip-to-gable lofts and 4–6 m rear extensions on ordinary 1930s semis are usually accepted. The council offers a paid pre-application service and decisions often run beyond 8 weeks, so 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.
