Side extensions in Sutton depend on the house. Typical homes here: 1930s semis and chalet bungalows in Cheam, Worcester Park, Wallington and Carshalton; Victorian and Edwardian terraces and villas in Carshalton, Sutton town and Wallington. Designations to check first: Conservation areas; Article 4 directions; River Wandle flood zones. Applications are decided by London Borough of Sutton and the Sutton Local Plan 2018.
The permitted development rules for side extensions
A single-storey side extension is permitted development on a house if it is no wider than half the width of the original house, no higher than 4 m, with eaves no higher than 3 m where it comes within 2 m of a boundary, and finished in materials similar in appearance to the house.
Anything wider than half the original house, any two-storey side extension, and any side extension on a flat needs planning permission. Garage conversions that keep the walls are usually permitted development; extending beyond them is assessed as a side extension.
What changes in Sutton
Side extensions are not permitted development in a conservation area at all, so there a planning application is always required.
The local constraints that most often decide the route in Sutton are listed below, taken from our Sutton area page. Each one is a reason to confirm the address on Sutton's constraints map before relying on permitted development.
- Conservation areas. Sutton has numerous conservation areas, including Carshalton Village, Cheam Village, Sutton Garden Suburb and parts of Wallington and Beddington. Source
- Article 4 directions. Some Sutton conservation areas, including Sutton Garden Suburb and parts of Carshalton, are understood to carry Article 4 directions removing permitted development for front alterations and boundary treatments.
- River Wandle flood zones. The Wandle rises at Carshalton Ponds and runs north through Carshalton, Hackbridge and Beddington. Source
- Green Belt and Metropolitan Open Land. The southern edge of the borough at Little Woodcote, Woodmansterne and Belmont includes Green Belt, and Beddington Park, Roundshaw Downs and other open spaces are Metropolitan Open Land.
- Trees and tree preservation orders. Sutton's suburban streets and larger plots carry many protected trees.
What Sutton planning officers look for
Side extensions that close the gap between semis, are flush with the front wall or carry a roof up to the main ridge are the most common refusal reason. Hip-to-gable lofts with rear dormers are routinely accepted outside conservation areas. Pre-application advice is available for a fee.
Fees and timelines
Sutton decides a householder application or a Lawful Development Certificate within 8 weeks of validation. The council fee is £528 for a householder application and £264 for a Lawful Development Certificate (England, from 1 April 2025; verify before applying).
Our own fee is fixed once quoted. The quote tool gives an indicative figure in minutes and a written quote follows within 24 hours.
Primary sources
- The Town and Country Planning (General Permitted Development) (England) Order 2015, Schedule 2: the permitted development limits quoted above.
- Planning Portal: do you need permission: the national guidance and the application service every council accepts.
- London Borough of Sutton: planning: the council's own constraints map, validation checklist and pre-application service.
