Residential slabs and footings
Site classification (A–P) and slab/footing design for Class 1 and 10 buildings.
Overview
AS 2870 is the standard for designing the slab and footing system for a house. It classifies the site by soil reactivity (A, S, M, H1, H2, E, P) and provides design tables for several slab types — waffle raft, stiffened raft, edge-beam — sized for the classification.
Key Requirements
- Site classification from a geotechnical investigation.
- Slab type matched to site class and building loads.
- Reinforcement schedule for the selected slab.
- Articulation joints for reactive sites.
- Edge beam dimensions and depth.
How it's used in the NCC
Called up directly by Part 4.2 of the Housing Provisions as the deemed-to-satisfy pathway for footings and slabs.
Practical Notes
- Always get the geotech report before committing to slab type.
- Class H and E sites can multiply slab cost — flag early to the client.
- Problem sites (Class P) need engineer-designed footings, not the AS 2870 standard tables.
Where to obtain
The full text of AS 2870 is published by Standards Australia and must be purchased — typical price A$150–400 per part. Always work from the current edition referenced in the NCC, not an older one.