A Bexley loft usually starts with the house type. On the 1930s semis of Bexleyheath, Welling, Sidcup, Blackfen and Barnehurst the hipped roof and the rear slope decide the design, and the question is how a rear dormer or hip-to-gable end sits on it. The Victorian and Edwardian terraces of Erith, Belvedere and Crayford share a roof line with their neighbours. The interwar detached houses of Sidcup, Bexley village and Foots Cray, and the older houses around Old Bexley and Hall Place, are the ones most likely to fall inside one of the borough's 23 conservation areas, where the route changes.
The permitted development rules for loft conversions
A loft conversion with a rear dormer is permitted development on a house if the added roof volume is no more than 40 m³ on a terraced house or 50 m³ on a semi-detached or detached house, the dormer sits at least 200 mm back from the eaves and no higher than the ridge, there is no dormer on the roof slope facing the road, materials are similar in appearance, and side windows are obscure-glazed.
Flats and maisonettes have no permitted development rights, so a loft to a top-floor flat always needs planning permission. Full-width box dormers that reach the ridge, and hip-to-gable conversions on semis whose volume exceeds 50 m³, also fall outside the allowance.
What changes in Bexley
Roof extensions are not permitted development in a conservation area, so a dormer or hip-to-gable there needs a householder planning application designed to the area's appraisal.
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's design guidelines say about a roof extension
Bexley's adopted Design and Development Control Guidelines SPD, which the council kept in force when the Local Plan was adopted in April 2023, sets three tests for roof extensions. A loft or roof space extension should not normally exceed the ridge height of the existing building, or be detrimental to the form of the existing roof by reason of its design or massing.
Dormers should if possible face the rear, and dormers on the hipped side of a pitched roof should in general be avoided. All roof extensions should be set back from the main wall of the house so they do not create the appearance of an extra storey. On a hipped 1930s semi that is why we design the dormer to sit on the rear slope rather than wrap the hip.
The council has also published a Part 2 design guide on building alterations and extensions, dated June 2026, which says it will replace the older guidelines once adopted. Its draft wording asks that no part of a dormer extend above the ridge, beyond the eaves or flanks, or wrap around the roof hips, and treats front dormers as unlikely to be accepted unless they are an original or common feature of the area. We check which document applies at the date of submission.
Conservation areas and Article 4 directions for attic rooms
Bexley lists 23 conservation areas, from Old Bexley, Parkhurst and Foots Cray to The Green and Longlands Road in Sidcup. The council says several Article 4 directions limit development without planning permission in some of them; four are listed: Brook Street, Old Bexley, Old Forge Way and Red House Lane. They are property-specific, so being inside the boundary does not tell you which applies.
Two of the directions mention attic rooms. In Old Bexley they bring attic rooms within council control for named properties on North Cray Road and Bexley High Street, and in Old Forge Way for the numbered houses listed in the direction. Brook Street and Red House Lane cover other works such as enlargements, chimneys, roofing materials, porches and boundaries. We read the direction for your exact number before choosing between a Lawful Development Certificate and a planning application.
What Bexley planning officers look for
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
- Bexley Council, Conservation and heritage
- Bexley Council, Article 4 directions
- Bexley Council, Design and Development Control Guidelines SPD
- Bexley Council, Design Guide SPD Part 2 (June 2026)
- Bexley Council, Old Bexley Conservation Area Article 4(2) Direction
- Bexley Council, Old Forge Way Conservation Area Article 4(2) Direction
- 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.
