Case 1 — sewer found on day one

A north London rear extension started excavation and exposed an unrecorded shared sewer running diagonally across the footprint. A build-over agreement was applied for, the design was revised to bridge the sewer, and the project resumed six weeks later.

Case 2 — soakaway in the wrong soil

A Surrey side extension included a soakaway designed on assumed clay loam. The actual ground was dense clay. The soakaway flooded the rear garden after two weeks. A redesigned attenuation tank and surface water sewer connection resolved it.

Case 3 — manhole hidden under decking

A homeowner inherited decking that covered a public manhole. Building Control required access reinstatement before sign-off on a separate extension. A removable hatch was retrofitted.