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Geotechnical Engineer

engineering

When you need one

Site class determination per AS 2870 (mandatory for any new dwelling), slope stability assessment, footing recommendation for non-standard soils.

Qualifications

Engineers Australia CPEng + Geotechnical Engineering specialty.

Professional body

Engineers Australia (Geotechnical College)

Typical cost (Site classification report + boreholes)

A$1,500–12,000

Per-state notes

Site classification is national under AS 2870. Class P sites trigger engineered footings (piles, screw piers, raft slabs).

Key outputs

✓AS 2870 site class (A / S / M / H1 / H2 / E / P)
✓Characteristic surface movement (ys) in mm
✓Borehole logs (typically 2-4)
✓Groundwater depth
✓Salinity + reactivity
✓Slope stability (if applicable)
✓Acid Sulfate Soils risk
✓Footing recommendation (slab type, pier depth)

What triggers engaging them

▸Every new dwelling (mandatory for AS 2870)
▸Class P (problem) sites
▸Steep slope (> 10° typically)
▸Fill > 600mm depth
▸Below water table

Notes

Geotech is often the first specialist report — its output drives footing cost (Class M slab vs Class P piles can be A$30,000+ difference). Get geotech BEFORE structural engineer for non-standard sites.