Site Classification Reports QLD | AS 2870 | Coastal Geo Consulting
A site classification tells your designer what the ground beneath the building is going to do. We investigate the site, test the soil to Australian Standard methods and issue an AS 2870 report your engineer can design a compliant slab and footing system from — without guesswork and without delays to your build programme.
What's in your site classification report
Every report we issue is built from field investigation and laboratory testing to Australian Standard methods — so your designer has measured data, not assumptions.
- Site class to AS 2870, with the calculated characteristic surface movement it is based on
- Borehole or test pit logs, with the soil profile described to AS 1726
- Laboratory test results — moisture content and shrink-swell testing to AS 1289
- Site observations covering slope, drainage, fill, vegetation and tree influence
- Practical foundation, site preparation and drainage recommendations
- RPEQ certification, suitable for building approval and council submission
When a site classification is required
A site classification is required before footing and slab design on virtually every residential build in Queensland, and it is typically a condition of building approval.
- New homes on single residential lots
- Duplexes, townhouses and small unit developments
- Extensions and additions with new footings
- Sheds, garages and secondary dwellings
- Lot-by-lot classification across new subdivisions
- Re-classification where site conditions have changed
If your site has cut and fill, established trees, uncontrolled fill or reactive clay, the classification is where those risks get identified — before they turn into a variation.
Understanding your site class
| Class | What it means | Surface movement |
|---|---|---|
| A | Sand or rock. Little or no movement from moisture change | Negligible |
| S | Slightly reactive clay | 0 – 20 mm |
| M | Moderately reactive clay or silt | 20 – 40 mm |
| H1 | Highly reactive clay | 40 – 60 mm |
| H2 | Highly reactive clay, greater movement potential | 60 – 75 mm |
| E | Extremely reactive | More than 75 mm |
| P | Problem site — needs project-specific engineering | Classified by condition |
A more reactive class does not mean a difficult build. It means the footing system needs to suit the ground. The cost risk comes from finding out late, not from the classification itself.
Read our full guide to site classification reports in Queensland →
Testing to Australian Standard methods
Reactivity cannot be judged by eye. Where a reactive profile is present, we test to the AS 1289 series:
- Moisture content — AS 1289.2.1.1
- Shrink-swell index — AS 1289.7.1.1, the primary reactivity test used for AS 2870 classification
- Atterberg limits and linear shrinkage — AS 1289.3.1.1 to 3.4.1
- Particle size distribution — AS 1289.3.6.1 where the profile is mixed
Results are combined with the design depth of suction change for your climatic zone to calculate characteristic surface movement under AS 2870 Appendix D. That number determines your site class — and it is stated in the report, not hidden behind it.
Field-based, not desktop-based
- Fast mobilisation — typically on site within 3 business days, with reports issued within 2 business days of fieldwork
- Queensland-specific — we work SEQ soils daily: reactive clays, coastal profiles, acid sulfate risk areas and fill-affected lots
- Construction-literate reporting — written so a builder can act on it, not just an engineer
- RPEQ-backed — signed certification satisfying statutory, council and contractual requirements
- Single point of contact — you deal with the person who was on your site
Where we work
South-East Queensland, Regional Queensland and Northern NSW. Based in Wamuran, servicing Brisbane, Moreton Bay, Sunshine Coast, Gold Coast, Ipswich, Toowoomba and surrounds.
Common questions
How long does a site classification take?
We typically mobilise to site within 3 business days of your booking, with the report issued within 2 business days of fieldwork being completed. Where laboratory shrink-swell testing is required, allow additional time for the testing turnaround. If your programme is tight, tell us early and we will work to it.
How much does a site classification cost?
Cost depends on lot size, access, the number of test locations required and whether laboratory reactivity testing is needed. Send through the site address and any plans you have and we will come back with a fixed quote.
What do you need from me to provide a quote?
Site address, lot and plan details, and a site or architectural plan if you have one. Proposed levels and any known fill or demolition history help us scope the investigation accurately.
Do I need a site classification or a full geotechnical investigation?
For a standard house on a conventional lot, an AS 2870 classification is usually the right scope. Retaining walls, steep sites, deep cuts, commercial buildings and civil works generally need a broader investigation to AS 1726. If you are unsure, send us the plans and we will tell you which you need.
My site has large trees. Does that matter?
Yes. Mature trees draw moisture from reactive soil, and removing them lets the soil re-wet and heave, sometimes over many years. Tree location, species and whether they are being retained or removed can change the classification and the footing advice.
Get a quote for your site
Send through the address and plans and we will come back with a scope and fixed price.