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Soil Testing

Getting Started

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:

  • The soil you build on will anchor your foundation
  • The type of soil you have onsite will determine the materials and designs used in your build
  • Your site classification will determine the cost of your foundations

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

We've designed our soil testing process so you get fast, accurate results
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Before we arrive onsite to drill, we check the job site via our extensive database. We access maps to compile all the relevant information we need, including underground services and site access.
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STA's soil testing technicians arrive onsite to complete the site investigation, drill into the ground, and remove soil samples.
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 Lab assessment and database check Icon

Lab assessment and database check

We bring the soil samples back to the lab for assessment, running them through a series of tests. In most cases, we also reference our database for site-specific data on local soils, wind ratings, and bushfire assessments.
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Site classification and QA check Icon

Site classification and QA check

Throughout the job, multiple quality assurance checks are conducted to ensure accuracy. Once the test results come through, we use them to classify the site.
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Report and certification Icon

Report and certification

Finally, we produce and send the reports and certification to the client, so they can use them for further planning, designs, and approvals.
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Why choose us?

Why get your soil tested with STA?

Experts in site classification Icon

Experts in site classification

With almost 30 years’ soil testing experience and thousands of tests through our lab every year, we're experts in our field.
Site-specific foundation design Icon

Site-specific foundation design

STA Consulting Engineers offers full service engineering. We design your foundations and structure to suit the ground conditions and the surrounding areas.
Analysis in our own NATA lab Icon

Analysis in our own NATA lab

We have our own NATA accredited laboratory where we thoroughly test and analyse materials. Because we're in full control over the testing process, we produce extremely reliable data for every project.
Regional soil profile maps Icon

Regional soil profile maps

With decades of data across hundreds of thousands of soil tests, we've developed local and regional profiles of soil compositions, along with wind ratings, bushfire assessments, and other “site estate specific” data.

“STA have been our go to engineers for soil testing, wind ratings and foundation designs for the last 20 years! STA offer an outstanding service to their clients and we couldn’t imagine working with anyone else. STA staff are always willing to go the extra mile and meet deadlines with an efficient and simply outstanding customer service focus. Brett Ward Homes can highly recommend STA Consulting Engineers for all of your engineering needs.”

Kirsty Ward // Business Co-Owner
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Get soil testing and site classification

Request a quote and we’ll get back to you with a service proposal within a week. Or call (07) 3071 7444 (QLD) or (02) 4032 6450 (NSW) to chat with our team right away.

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Our work

Recent soil testing projects

We test and classify thousands of sites around Australia every year

Tell me more about 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.

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.

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.

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.

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.

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

Usually, soil testing results are delivered in 10 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.

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.

Got more questions about soil testing or site classification?

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