Melbourne sits on a varied geological patchwork. In the inner suburbs, you often hit the notorious Coode Island Silt – a soft, compressible estuarine clay that can reach 30 metres deep. Out towards the east and north, the ground changes to basalt-derived clay and sandy terraces from the Yarra River system. For any shallow foundation design in Melbourne, understanding that local variability is the first step. We start every project with targeted boreholes and in-situ testing, typically combining a test pit investigation for shallow profiles with SPTs to capture strength at depth. That dual approach gives us the data we need to propose safe, economical footing sizes without over-designing.
For Melbourne's basalt clays, seasonal moisture change can shift bearing capacity by 30% – design for that movement or repair cracks later.