Soil Testing: Why it’s important when building a new house

The very nature of the land you build on is the biggest factor of a building project and the one aspect that is important you get right on the onset.

Getting a soil test will provide the information needed to understand what’s happening underground and how to build on it.

Take note that not all soil test results are the same.

There are differences in how tests are done on-site, in the quality and readability of the soil test report, and potentially even differences in the final site classification given for the block. Even though all soil tests for residential building projects must conform to the same Australian Standards for single dwelling houses, townhouses, and similar structures.

The main reason is to understand how ‘reactive’ the soil is, and ensure that there aren’t any chemical or physical conditions on the site that might damage your house. Soil reactivity refers to how much the soil on the site is likely to move, expand and contract (normally as a result of changing moisture content) and is graded by class.

The soil bearing capacity tells us the weight the soil can support per unit area and determines the type of footings or slab subfloor that can be built on your site.

2 Components of Soil Test:

  1. Field soil analysis to collect soil, data and site measurements
  2. Laboratory tests on the soil samples taken

The field component includes the extraction of soil samples, documentation of the existing soil strata, and collection of field data, such as bearing capacity – thereby determining the suitability of the soils to place load upon it e.g. weight of dwelling.

It is also a requirement as part of the site investigation, to document other factors that may affect the long-term stability of the designed foundations, e.g. trees, drainage, slope, existing structures, etc.

The lab component involves undertaking laboratory tests so as to determine the soil’s capacity to swell and shrink in the course of the life of the dwelling under normal site conditions.

When is soil testing needed?

It is a government legislative requirement that all new residential construction requires a soil test and site classification in order to design fit-for-purpose foundations.

  • The soils are the foundation of the proposed structure, on which the entire build relies to perform over the service life of your home.
  • The type of soil you have on-site will determine the materials and designs used in your build.
  • The site classification may dictate the method, complexity, and cost of your foundations.

Builders need to know the soil type the property is going to be built on so that can allow for the correct foundations to be factored into the building cost and also the plans.

This is just one of the many aspects of a good builder’s task to construct the best property for our clients.

We ensure that all our properties secure a soil test and site inspection report prior to construction.

Source:, Australian Standards: CE-009 : Testing Of Soils For Engineering Purposes

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