Case 1 — depth halved by an honest mistake

An engineer's depth of 1.8m was misread on site as 1.0m. Picked up the morning of the pour. Trench extended same day, concrete delayed by twenty-four hours. Total extra cost — small. Cost if poured — far larger.

Case 2 — drain across the trench

An unrecorded clay drain ran across the rear elevation. The trench had been excavated through it. Drain protected with lintels and concrete encasement, design signed off by the engineer, build-over agreement applied for retrospectively. Three week delay.

Case 3 — soft seam discovered mid-pour

Concrete pump turned off after a soft layer became visible in the trench wall. Engineer attended within the hour, specified additional depth in that bay. Avoidable with a pre-pour walk, but the right call once it surfaced.