Side extensions in Bexley depend on the house. Typical homes here: 1930s semi-detached houses in Bexleyheath, Welling, Sidcup, Blackfen and Barnehurst; Victorian and Edwardian terraces in Erith, Belvedere and Crayford. Designations to check first: Conservation areas; Thames and Cray flood risk; Green Belt and Metropolitan Open Land. Applications are decided by London Borough of Bexley and the Bexley Local Plan (2023).
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 Bexley
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 Bexley are listed below, taken from our Bexley area page. Each one is a reason to confirm the address on Bexley's constraints map before relying on permitted development.
- Conservation areas. Bexley has a modest number of conservation areas, including Bexley Village (Old Bexley), and several historic centres and estates. Source
- Thames and Cray flood risk. Erith, Belvedere, Thamesmead, Slade Green and the Crayford Marshes lie in Flood Zones 2 and 3 behind the Thames defences; the River Cray and Shuttle also carry fluvial flood risk. Source
- Green Belt and Metropolitan Open Land. Foots Cray Meadows, the Cray valley, Lesnes Abbey Woods and Crayford Marshes include Green Belt and Metropolitan Open Land. Source
- Article 4 directions. We are not aware of a borough-wide Article 4 direction removing householder permitted development in Bexley, but directions may exist for specific conservation areas or for houses in multiple occupation. Source
What Bexley planning officers look for
Officers focus on the 45-degree test from neighbouring windows, the depth of single-storey rear extensions beyond the neighbour, and whether two-storey side extensions are set back from the front wall so that pairs of semis do not merge into a terrace. Front dormers and flat-roofed dormers that wrap the hip are the usual loft refusals. The council generally offers a paid pre-application service. Decision times are usually close to the statutory 8 weeks, though a formal extension of time is not unusual.
Fees and timelines
Bexley 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 Bexley: planning: the council's own constraints map, validation checklist and pre-application service.
