Do I need a geotech report for my DA?
A common question once council comes back with conditions. Here's when a geotechnical report is required, what's in it, and what it costs.
When you'll need one
A geotechnical report goes further than a basic site classification. You will usually need one when:
- your site slopes, or has cut and fill;
- the project involves a basement, deep excavation or piering;
- there are retaining walls, a watercourse or unstable ground nearby;
- the land contains uncontrolled or unknown fill;
- your council or structural engineer asks for one as a DA condition.
For a straightforward flat block, a site classification to AS 2870 is often all that's needed.
What's in the report
A geotechnical report describes your ground conditions and tells your design team how to build on them safely. It typically covers the soil profile, bearing capacity, groundwater, slope stability and any fill, along with practical recommendations for footings, excavation, retaining and earthworks.
Cost and turnaround
Cost depends on access, the number of test locations and the complexity of the site. Most residential geotechnical reports are completed within one to two weeks of testing. The investment is small compared with the cost of redesigning footings — or a stop-work — once the excavator is on site.
Talk to a soil & site expert
We prepare council-ready soil, geotechnical and DA reports right across Sydney. Call with your site address for clear advice.