When planning to build a new home or undertake major renovations, one of the most critical—but often overlooked—steps is soil testing. Before the first shovel hits the ground, understanding the condition of the soil beneath your future home can save you time, money, and potential headaches down the line.
At Residential Engineering, we’ve seen the impacts of a lack proper soil testing on residential projects firsthand. Here’s why it matters—and what you should expect.
What Is Soil Testing?
Soil testing, otherwise known as a geotechnical investigation, is the process of analysing the physical and chemical properties of the soil on your building site. It helps determine behaviour of the soil profile to allow for adequate design and support for any type of structure.
In Australia, soil testing is essential for designing safe and compliant foundations, especially considering our diverse range of soil types—from reactive clay soils to sandy coastal terrain and anything in between.
Why Is Soil Testing Important Before You Build?
1. Foundation Design
The soil type directly influences what type of foundation will be most suitable for your home. For example, conventional bored piers may be best suited for sites with stiff clay or rock whereas steel screw piles may be better suited where deeper piers are required for poor, dry and loose material such as sand. Soil testing assists in the design of engineered foundations that work in conjunction with site specific conditions.
2. Structural Adequacy
A design which doesn’t align with site specific soil conditions can lead to subsidence, uneven floors, wall cracks, and long-term structural damage. Identifying these risks early allows for preventative engineering solutions.
3. Cost Efficiency
Without soil testing, builders may use generic foundation designs that are either insufficient or unnecessarily expensive. A tailored foundation based on soil data ensures you’re not overbuilding or under-designing your home.
4. Compliance with Australian Standards
Australian building codes require soil classification and appropriate foundation design. Soil testing ensures your project complies with AS 2870 – Residential Slabs and Footings and other relevant standards.
What Happens During a Soil Test?
At Residential Engineering, our soil testing process is thorough and transparent:
Step 1: Site Visit and Sampling
Our geotechnical engineers visit your site to collect soil samples using a drilling rig or hand auger. Samples are taken at various depths to understand the soil profile.
Step 2: Laboratory Analysis
The samples are analysed in a lab to determine:
- Soil type and classification (e.g., Class A, S, M, H, E, P)
- Moisture content
- Allowable soil capacity
- Reactivity and shrink-swell potential
- Presence of organic material or contaminants
Step 3: Reporting and Recommendations
We provide a detailed soil report that includes:
- Site classification
- Foundation recommendations
- Drainage considerations
- Potential construction challenges
This report is essential for your builder, architect, and structural engineer to design a safe and cost-effective foundation.
Common Soil Types in Australia
Australia’s soil conditions relevant to design vary widely. Here are some common classifications:
- Class A – Stable, non-reactive soil
- Class S – Slightly reactive clay
- Class M – Moderately reactive clay
- Class H – Highly reactive clay
- Class E – Extremely reactive clay
- Class P – Problematic soil (e.g., soft soils, fill, or landslip-prone areas)
Each class requires a different engineering approach to ensure structural integrity.
When Should You Conduct Soil Testing?
- After purchasing land for construction
- Prior to designing foundations or slabs
- When planning extensions and alterations to your existing home
- When completing retaining works greater than 600mm in height
Why Choose Our Geotechnical Engineering Services?
As a trusted name in Australian residential structural engineering, we offer:
- Local expertise – We understand the unique soil conditions relevant to specific areas across NSW
- Qualified geotechnical engineers – Accurate testing and reliable reporting
- Tailored solutions – Designs that match your site’s needs
- Fast turnaround – Efficient testing to keep your project on schedule
Soil testing isn’t just a technical formality—it’s a foundational step in building a safe, durable, and compliant home. At Residential Engineering, we help homeowners and builders make informed decisions from the ground up.
If you’re planning to build or renovate, contact us today to schedule your soil test so you can build with confidence.