A sunken section of garden, lawn or driveway often indicates that an underlying drain has been leaking and washing away the supporting soil over a sustained period. The classic pattern is a soft, dishing depression running along the line of the drain, sometimes with visible cracks in nearby paving. Causes include cracked pipework, displaced joints, root intrusion and partial collapses, all of which allow water and fine soil to migrate into the pipe. In London, where many older drains run close to garden walls and shallow driveways, the issue can be progressive and lead to wider settlement if left untreated. Engineers usually carry out a CCTV drain survey in accordance with BS EN 13508-2 to identify the source. Repair typically involves relining or excavation, followed by reinstatement of the ground.
Sunken garden or driveway
Localised ground depression caused by drain leakage washing away supporting soil.
