Drainage laid with wrong bedding or insufficient cover
What it looks like
Deformed or cracked pipework found at CCTV survey, standing water in the run, or settlement over the trench line after backfill.
Why it happens
Pipes bedded on site-won material, surround compacted with a mechanical whacker directly over the pipe, or insufficient cover under a trafficked area.
What it costs if it is missed
Failed drainage tests, excavation of finished driveways and gardens to correct, and delay to plot handover.
How to inspect for it
Inspect open trenches before backfill: bedding material and depth, side fill compaction by hand, cover depth checked against the location, and a proving test recorded before the trench is closed.
How to prevent it
Test and photograph while the trench is open. A drain that has passed a recorded air test before backfill is the cheapest inspection on site.
Basis in regulation
Last updated 23 August 2026. This is our editorial summary of publicly available regulation and site practice, not building control approval or a warranty determination.