Question 1

When do I need a geotechnical investigation?

Accepted Answer

Current NCC and AS 2870 practice expects a geotechnical investigation for every new residential build to confirm site classification and inform the footing design. Any retaining wall, regardless of height, also typically requires geotechnical input.

Question 2

What is site classification?

Accepted Answer

A classification of ground reactivity (A, S, M, H1, H2, E, P) under AS 2870 that drives footing design — reactive sites typically require stiffer raft systems or piers.