Lagos sits on a mosaic of coastal sands, soft clays and reclaimed ground. Two sites a kilometre apart can behave completely differently under the same building, which is why soil investigation must come before foundation design, not after.
What a proper investigation includes
A useful report combines boreholes, trial pits, standard penetration tests and laboratory analysis. It should tell you the bearing capacity, settlement characteristics, groundwater level and chemical aggressivity of the soil.
What happens when it is skipped
Foundations sized on assumption either over-spend on unnecessary concrete or under-perform and crack. Remedial works on a failed foundation are among the most expensive problems in construction, because everything above them is already built.
Designing for the ground you have
Depending on results, we may recommend raft foundations, ground improvement, piled foundations or a combination. The right answer is the one that performs over the building's life at the lowest whole-life cost.
The practical takeaway
Commission the investigation early, share it with the structural engineer before design is fixed, and keep a contingency for ground risk. It is a small line in the budget that protects everything above it.