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 Epsom and Ewell
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 Epsom and Ewell are listed below, taken from our Epsom and Ewell area page. Each one is a reason to confirm the address on Epsom and Ewell's constraints map before relying on permitted development.
- Green Belt. A large share of the borough is Green Belt, including Epsom Common, Epsom Downs, the Hogsmill open space and land around Horton and Langley Vale. Where planning permission is needed, extensions to houses in the Green Belt must not be disproportionate to the original dwelling, and outbuildings face a stricter test on size, siting and effect on openness. Check the council's constraints map to see whether your plot is inside the boundary. Source
- Conservation areas. Epsom town centre, Ewell Village, Stamford Green and Woodcote are among the borough's conservation areas. Roof extensions are not permitted development inside them, and officers apply the character appraisal to extensions, dormers and boundary treatments. Check the council's constraints map for the exact boundaries before relying on permitted development. Source
- Hogsmill River flood risk. The Hogsmill River rises at Ewell and runs through Ewell Village, West Ewell and on towards Kingston, and land alongside it and its tributaries sits in Flood Zones 2 and 3. Ground-floor extensions, basements and outbuildings there may need a flood risk statement with the application. Source
- Article 4 directions. The council has used, or has consulted on using, Article 4 directions to remove particular permitted development rights, including for converting houses into small houses in multiple occupation and for works in some conservation areas. The position changes over time, so check the council's constraints map and current directions for your address before relying on permitted development. Source
- Listed buildings. Ewell Village, Epsom town centre and the old hospital estate at Horton contain listed houses, cottages, churches and institutional buildings. Listed building consent is needed for almost any alteration, internal or external. Source
What Epsom and Ewell planning officers look for
Epsom and Ewell Borough Council officers assess householder applications against the Core Strategy, the saved Development Management Policies and the council's supplementary guidance on residential extensions, with the emerging Local Plan carrying growing weight. On the 1930s semis that dominate Stoneleigh, West Ewell and Ewell they tend to look for two-storey side extensions set back from the front wall and below the main ridge, a gap kept to the side boundary so the pair does not read as a terrace, and rear extensions that pass the 45-degree test to the neighbour's nearest habitable window. In Woodcote and around Epsom Downs plot coverage, tree protection and the spacious character of the road carry more weight. In the Green Belt officers usually measure the extension against the original dwelling by floorspace or volume and treat outbuildings more strictly. Common refusal reasons are full-width box dormers, side extensions that create a terracing effect, and roof extensions on front slopes in conservation areas. The council offers a paid pre-application service. Decisions can run past the statutory 8 weeks; allow 8–12 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.
