When you’re building a new home it’s easy to get caught up in planning all the fun details. The reality is that house builders Brisbane actually need to know more than what type of flooring you want to install. There’s lots of preparation involved with a building project, but one of the most important puzzle pieces is soil testing. The Importance of Soil Testing When Building a Home determines lots of things about how your home is designed and engineered, so it’s critical to the entire process.

What is Soil Testing?

Soil testing is a big part of the home building process. Most modern homes are built on concrete slabs laid directly over the ground beneath, so that means the quality of the soil has a big impact on the stability of your house. Soil testing is compulsory in most Australian states and is carried out by professional geotechnical engineers. The engineer will take samples from your block of land for testing and review, and they’ll return to you with a soil classification. That soil classification can then be used by your builder to design a slab, footing or other foundations for your home.

How is Soil Testing Performed?

Soil testing is performed by licensed geotechnical engineers. They visit your site and use specialised hollow drills to take “core” samples from the ground. These cylindrical samples of soil are then taken back to their facility for analysis and testing. The major benefit of this type of soil testing is that it reveals what’s going on underneath the ground. Depending on your needs, soil testing can be done at depths anywhere from 10 centimetres to several metres, although residential builds usually only take shallow samples.

When performing soil sampling for a construction project, it’s important to take samples from all over the site. Soil composition can vary from one area to the next, so it’s common for engineers to take dozens of samples from every part of the block.

Australian Soil Classifications

The soil that’s taken away from your site will be tested and given a soil classification. Soil classifications are a measure of how reactive the ground is. That is, how much the ground changes or moves when it’s subject to external factors such as moisture absorption. Stable soil that shows less movement is considered less reactive, while highly reactive soils expand and contract noticeably with moisture absorption.

Soil testing is a major part of the Australian construction industry and is regulated by Australian Standards. According to AS2870, Australian soils are grouped into several classifications:

Other Soil Classification Factors

Soil classifications aren’t the only thing house builders Brisbane pay attention to. To ensure your new home is stable and protected from shifts in the land underneath, builders also consider other factors:

• Erosion – Soil classification is effectively a measure of how much soil shifts when it absorbs water. This creates an additional problem, because water causes soil to erode away over time. Eroding soils can hollow out support from underneath your slab, eventually leading to severe foundation cracking and other structural problems.
• Bearing Capacity – The weight of a house pressing down on soil is significant. Bearing capacity is a measure of how much weight the soil in an area can safely hold. It’s possible for a soil to be low reactive but also have low bearing capacity. If that’s the case, the ground will require additional compaction or other treatments to stabilise the foundations.
• Seasonal Changes – Rainy and drought periods can cause major shifts in soil. In areas that are prone to these seasonal changes, engineers need to pay attention to how much the ground shifts over time. In rainy periods the ground may swell and crack the foundations. In dry periods the ground may shrink and remove support away from vital footings. In either case, your building engineer will need to develop drainage and stabilisation systems that minimise the impact of seasonal changes.