A standards-controlled workflow for residential site classification under AS 2870, designed for engineering review.
AS 2870 Site Classification Assessment Workflow
Residential site classification brings together subsurface information, soil reactivity, moisture conditions, fill, groundwater, slope and other site features that can affect footing performance. The NCC Housing Provisions require relevant foundations to be classified in accordance with AS 2870.
Note: This page describes an assessment workflow and does not reproduce AS 2870 classification thresholds, calculation procedures or controlled tables.
Assessment inputs
- Site address, proposed development and investigation date
- Borehole or test-pit locations, depths and ground levels
- Soil and rock profile with AS 1726 descriptions
- Fill type, depth, control status and evidence
- Atterberg limits, shrink-swell or other approved reactivity test results
- Groundwater and drainage observations
- Trees, abnormal moisture sources and site history
- Slope, erosion, instability, soft ground, collapse or other problem conditions
- Climatic and design inputs required by the approved method
Assessment sequence
- Confirm that the investigation coverage is suitable for the proposed building area.
- Validate soil descriptions and laboratory results.
- Establish the reactive-soil profile and the method used to assess characteristic movement where applicable.
- Check problem-site conditions before assigning a normal reactive class.
- Apply the complete classification rules from the licensed AS 2870 method.
- Record limitations, abnormal moisture conditions and recommendations.
- Require engineer approval before the classification appears in a final report.
Problem-site controls
A numeric reactive-soil result should not override conditions that require a problem-site pathway. Explicit checks should be made for fill, soft or collapsing ground, slope instability, erosion, mine subsidence, abnormal moisture, uncontrolled drainage and other conditions defined by the applicable requirements.
Characteristic movement record
Where the approved method includes a characteristic surface movement assessment, the record should capture:
- Each contributing soil layer
- Test parameter source and sample depth
- Moisture-change and depth assumptions
- Calculation method and standard edition
- Layer contribution and total result
- Any engineer adjustment and reason
The calculation must not infer site class from plasticity index alone.
Output controls
- Final class and any qualifying suffix
- Problem-site reason where applicable
- Investigation and laboratory references
- Standard edition and approved internal method version
- Assumptions, limitations and footing-design boundary
- Engineer name, approval date and revision
Related Resources
- Site and Lot Classification
- AS 2870 Site Classes
- Shrink-Swell Testing
- Soil Classification Workflow for AS 1726