If you’re an architect managing a client’s residential project or a homeowner undertaking an extension to your property, chances are you’re going to need a geotechnical report. If you’re excavating into a sloping site, or putting in a new swimming pool, or digging out a new basement level for your house, your structural engineer (that’s us!) is definitely going to need a geotechnical report. The purpose of this article is to outline why and when you’ll need a report; how you and your consultants (plus your builder) can benefit from it; and what to look for. Some of the descriptions and examples we’ll discuss below reference the suburbs and geography of Sydney, but the principles are the same Australia-wide.