Successful builds start with soil testing and site classification
Soil testing is critical for successful building projects, and in many cases, site classification is a compulsory first step in the building process. And for good reason:
It’s important to understand your soil before you start planning your build or designing your foundations. And the best way to do that is to work with experienced soil testing and site classification consultants.
STA Consulting are Australia’s leaders in soil testing services. We’re experts in soil compositions, the impact they have on foundation design, and how to engineer site-specific foundations for structurally sound residential and commercial buildings. With almost 30 years’ experience, our own NATA accredited laboratory, and regional soil profile maps, we’re uniquely equipped to deliver more accurate, comprehensive results.
Whether you’re planning a small residential build, multi-storey home, apartment building, aged care facility, industrial building, or something else… we’re here to help you get that first step right.
Our soil testing process
Lab assessment and database check
Site classification and QA check
Report and certification
Why choose us?
Why get your soil tested with STA?
Experts in site classification
Site-specific foundation design
Analysis in our own NATA lab
Regional soil profile maps
Kirsty Ward // Business Co-Owner
Get soil testing and site classification
Tell me more about soil testing
What is soil testing?
Soil testing is done by specialist soil testing technicians to collect information about the type of soil at a building site so that structural engineers can recommend and design the appropriate foundations for that site.
It’s also sometimes referred to as site classification, because after the soil samples are taken and tests are complete, the site can be classified. Site classification in Australia involves giving a set rating (Class A, S, M, H1, H2, or E) to soil based on the Australian Standard AS2870. These classifications refer to the level of reactivity/movement in the soil as moisture content increases or decreases.
Specialist soil testing companies collect the soil sample onsite before testing it in a lab (ours is NATA accredited), then engineers analyse the results to provide a classification that’s delivered in a report. Many engineering consultancies (like STA) can also provide custom foundation designs to suit the site conditions.
Why and when is it needed?
Soil testing and site classification are an important first step in a building project as it involves testing a sample of soil from the site to understand the site’s soil characteristics. These problems include soil that’s too soft or loose, soil that’s too wet, and clay soil that reacts by increasing or decreasing in volume as moisture levels change.
It’s critical to scope out your site and look for potential conditions that might damage a building or impact the foundation and structural requirements. The information from soil testing will be used to determine the right foundations and footings so that the building can handle the soil movement as it expands and contracts. The wrong foundations can cause cracking, issues with windows and doors sticking, and shifting foundations, so it’s important to get this right.
The best time to organise soil testing is usually after you’ve chosen the location for your building, but before preparing your plans.
What are engineers looking for in the soil?
When your engineers test your soil, the main thing they’ll be looking for is “soil reactivity”.
This covers the likelihood of the soil moving, expanding, and contracting as the soil dries out or gets saturated with rainwater. The more reactive your soil, the more potential for problems if the wrong materials are used. The data your engineers collect from your soil will enable them to classify your site, which will impact the type of foundations and structural elements used in your building.
It’s very important to know your soil’s reactivity so your structural engineers can choose the best suited foundation materials and designs, with enough bearing capacity to support your structure.
How do we do soil testing at STA?
We test your soil by visiting your site and collecting a sample. We take more soil samples than most, to ensure an accurate site classification.
Depending on the project type and site, we collect soil at a range of depths, up to 5m deep. We’ll usually take soil samples from multiple locations onsite, in case there are different soil types present. We take this soil back to our NATA accredited LAB for testing.
We have the following tests available to help classify sites:
- Atterberg limits
- Shrink swell
- Liquid limit level
- Linear shrinkage
- Salinity (where required)
We then use the test data to classify your site and write your report.
What are problem soils?
The main “problem soil” is clay soil because it can be highly reactive – prone to expand and contract as moisture levels change.
With longer drought periods in Australia broken by heavier rainfall, clay soils can present a real problem for buildings. The right foundations designed to suit specific site conditions are critical to ensure homes and other buildings are designed to last.
What are the different soil classifications?
Soils usually sit under one of the following classes:
- Class A – Probably sand or rock. Stable and unlikely to react or move as water levels increase or decrease.
- Class S – Probably some clay content. As water levels in the ground go up or down, the ground may move a little.
- Class M – Probably a moderate amount of clay or silt. It’s likely that moisture changes will cause a reasonable amount of movement.
- Class H – A clay site that’s highly reactive. Expect a lot of ground movement as moisture levels increase or decrease.
- Class E – A clay site that’s extremely reactive. As the ground moisture level goes up or down, expect a substantial amount of movement.
- Class P – A “problem” site where soil will struggle to bear a load evenly or “where ground movement may be significantly affected by factors other than reactive soil movements due to normal moisture conditions” (AS2870, clause 2.1.3). Class P grades are often given due to potential coastal erosion, soft soils, improperly compacted fill, moisture issues, dams, trees, and poor drainage, among other reasons
How long will my soil testing take?
Usually, soil testing results are delivered in 10 business days, plus an allowance (of around 8 days) for travel time if it’s a regional area. We always try to visit a site within 3 days (but this could take more time, depending on the location), then spend 2 days in the lab. We use the remainder of the time to compile your report and sign it off.
Do I also need geotechnical services?
In some cases, you’ll need to go beyond soil testing to fully understand your site so that you can select the most suitable foundation and designs. Some development sites are more complex than others due to slope stability issues, fill issues, piling requirements, and issues with clay. In that case, geotechnical services will be recommended to understand the landscape better before construction starts.