Slab edge and footing clash on a sloping site
A builder is constructing a single-storey residence on a 1-in-8 cross-fall block. The engineer's design shows strip footings founded at 600 mm below natural ground surface, with a slab-on-ground edge beam 300 mm deep. During excavation, the site supervisor reports that on the uphill side the footing bearing stratum is soft clay to 1.2 m, while on the downhill side rock is encountered at 350 mm. The building surveyor has already approved the footing inspection on the downhill side but has not inspected the uphill side. Concrete is booked for tomorrow morning and the pump truck has a cancellation fee of $1,800. The client is pressing for progress because their rental lease ends in six weeks.
1. What should the builder do before the concrete truck arrives, and why?
Read the worked answer
The builder must not pour on the uphill side. The approved inspection covers only the downhill footing; the uphill footing has not been inspected and, more importantly, has not been founded in the stratum the engineer assumed. Soft clay to 1.2 m means the 600 mm founding depth does not reach competent bearing material, so the footing as designed cannot be verified.
The correct sequence is: (1) stop work on the uphill side and record the exposed bearing surface with photos and levels; (2) notify the engineer and the building surveyor, providing the excavation depths and a description of the material; (3) obtain written direction - likely a deeper footing, an enlarged pad, or piering to a stiffer layer - and have the surveyor inspect before covering. The downhill side may proceed if the surveyor's approval is current and the rock is correctly founded.
The $1,800 cancellation fee and the client's lease deadline are commercial pressures, not technical justifications. Pouring over unverified bearing material risks differential settlement, cracking and a non-compliant footing that cannot be remedied without demolition. The builder should also check whether the cancellation can be deferred by pouring only the approved section and rebooking the pump for the remainder.
2. The client asks the builder to 'just pour it and sort it out later'. How should the builder respond, and what records should be kept?
Read the worked answer
The builder should decline clearly and in writing, explaining that covering uninspected, unverified footings would breach the building approval conditions and the builder's own contractual and statutory obligations. A verbal refusal is not enough; the response should be an email or site instruction note that records the client's request and the builder's refusal.
Records to retain: the engineer's original drawings and any revised details; the surveyor's inspection certificates for each stage; dated photographs of the excavation showing depth against a staff or tape; levels taken at the bearing surface; the engineer's written direction; and the correspondence chain including the client's instruction. These records protect the builder if the client later alleges delay or claims the builder should have proceeded.
It is also worth explaining the practical consequence: if the footing fails, the remedy is underpinning or partial demolition, which costs far more than the delay and may not be covered by insurance. Framing the refusal as protecting the client's asset, not just the builder's liability, usually resolves the pressure without confrontation.