A raised patio or decking platform more than 300mm above ground level needs planning permission from Bexley Council — below that threshold it is usually Permitted Development. Garden rooms and outbuildings are permitted under Class E within the standard limits (single-storey, under 2.5m eaves within 2m of any boundary, under 4m ridge height on a dual-pitched roof, covering less than 50% of the garden), but Bexley's conservation areas (Old Bexley, Lamorbey, Bexleyheath Broadway) restrict these rights further and a full application is the safer route. London Plan SuDS principles also apply to any new hard surface in the rear garden.

Bexley sits on London Clay bedrock, typically overlain by Taplow Terrace gravels at 0.8–3m depth. The clay shrinks and swells with seasonal moisture — the usual cause of lifted slabs and cracked pointing on older Bexley patios. We counter it with a deeper MOT Type 1 sub-base, a geotextile membrane across the subgrade, and flexible jointing throughout. Where Taplow gravels are close to the surface (common in Crayford and Erith) infiltration is better and a soakaway is feasible; across most of Bexleyheath and Sidcup the clay prevents infiltration and surface water needs piping to the nearest drain.

Bexley's three main conservation areas — Old Bexley village, Lamorbey and Bexleyheath Broadway — carry Article 4 directions that remove Permitted Development rights for raised terracing, boundary walls over 1m on a highway, outbuilding alterations and some material changes. Within these areas a planning application to Bexley Council is typically required for works that would be PD elsewhere. The London Plan's SuDS-first drainage policy also applies borough-wide, so any new hard surface — even where PD — should use permeable materials or include surface-water drainage plans. We check the conservation-area boundary at survey stage and advise on planning and drainage requirements upfront.