AS 2870 Site Classes — Slabs & Footings
AS 2870 Site Classes — Slabs & Footings
Before the slab goes down, the soil gets classified — and the reactivity class drives your footing design. It is the line on the geotech report everyone skips to.
Site classification (AS 2870-2011)
| A | Stable — little or no ground movement (rock, sand) |
| S | Slightly reactive clay/silt |
| M | Moderately reactive |
| M-D | Moderate, with deep-seated moisture changes |
| H1 | Highly reactive |
| H2 | Very highly reactive |
| E | Extremely reactive |
| P | Problem site — always specific engineering |
What a 'P' site covers
- Soft or unstable soils, uncontrolled fill, mine subsidence, landslip, creep, erosion or abnormal moisture — engineered case-by-case, not from the standard tables
Before you pour
- Geotech site-classification report
- Structural footing certificate (to AS 2870 / NCC)
- Footing-stage inspection before the slab pour
Reference only — footing design must come from a qualified engineer for the specific site. AS 2870-2011 is the NCC Deemed-to-Satisfy standard for residential slabs and footings.
Sources: AS 2870-2011 Residential slabs and footings · ABCB / National Construction Code
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