Geotechnical site classification defines the soil reactivity and ground conditions that influence slab and footing design for buildings. It ensures foundations are designed to withstand ground movements caused by moisture changes, consolidation, fill, or slope instability.
Key Standard
AS 2870-2011 – Residential slabs and footings – Construction
(Referenced by the National Construction Code and councils across Australia.)
Classification Types (AS 2870 Table 2.1)
How It’s Determined
Soil Sampling & Testing
Boreholes/test pits to 1.5–3 m depth.
Laboratory tests: Atterberg limits, moisture content, particle size, and soil suction.
Soil Profile Interpretation
Identify layers, depths, and groundwater.
Moisture Reactivity & Ground Movement
Estimate the characteristic surface movement (ys).
Classification Assignment
Apply AS 2870 criteria using ys and soil plasticity.
Additional Conditions
Slope, fill, erosion, or soft ground may alter classification to P.
Applications
Determines footing type: slab-on-ground, stiffened raft, pier and beam, waffle, or deep footings.
Guides earthworks and drainage design to minimise soil moisture variations.
Required for building permits and engineering certifications
Contact
Support
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