How Soil Type Can Cost You Money

How Soil Type Can Cost You Money

Stroud Homes offer FREE site evaluations

Free site evaluation

Many people do not realise how much the soil type of their land can affect the cost of the home. Soil type can in fact increase the cost of your home by thousands of dollars.

Luckily, Stroud Homes can often avoid the extra costs with help of a Free Site Evaluation. We speak to Stroud Homes Toowoomba about different soil types and why it’s important to learn about them.

Why is soil type so important?

It is necessary to complete a soil test before building to understand how much the site is going to move, expand and contract; they grade these by class.

The soil bearing test also tells your builder how much weight the soil can bear per square unit, therefore determining whether your home will be built on a slab or stumps. If the soil is unstable, footings may also be required to be placed deeper into the ground.

How many different soil types are there?

There are seven types of soil grades, here’s a quick guide:



Includes many sand, gravel and rock sites with no clays. These sites have no expected movement and as a result zero moisture variation.


Slightly reactive sites which exhibit only small movements with moisture variation.


Moderately reactive sites exhibit moderate amounts of movement with moisture variation. These sites commonly include red/brown silty soils, some sandy clays and loamy soils.


Highly reactive sites exhibit high amounts of movement with moisture variation. These sites include some silty clays in the Toowoomba area and many of the sandy clays and basaltic clays in the Lockyer Valley.


Highly reactive sites exhibit very high amounts of movement with moisture variation. These sites include some silty clays in the Toowoomba area and many of the sandy clays and basaltic clays in the Lockyer Valley.


Extremely reactive sites which exhibit greater than 75mm of surface movement. Typically, these sites include deep reactive clays, such as black and dark brown soils on the Darling Downs, but are also found throughout the Lockyer Valley and parts of Toowoomba. These sites typically demand quite expensive footing systems.


Problem site. As indicated previously, the Site Classification must consider many aspects of the site, not just the reactivity of the soil. P sites are those that include other factors that need to be brought to the attention of the owner, builder and footing designer. A ‘P’ classification does not indicate a specific value and is described as a ‘problem’ site.

The reasons for a P classification include:

  • Growth and/or removal of trees will cause abnormal moisture conditions in the subsurface soils.
  • Unusually high moisture conditions caused by water flow, ponds, dams etc.
  • Sites with fill which can be either ‘controlled’ or ‘uncontrolled’. The P Classification depends upon the depth and type of fill.
  • Sites with poor bearing capacity, soft soils, or soils which are prone to collapse.
  • Sites prone to mine subsidence, land slip, piping or coastal erosion.
  • Sites which for one reason or another cannot be classified as normal sites.


Can you build on any soil for the right price?

Understandably, receiving a ‘reactive’ soil test may put you off building altogether.

Just remember, as frightening as the reports may seem, millions of homes have been built on these soil types and have been standing for decades or even centuries without damage.

However, reactive soil reports do make sticking to a budget more difficult.

This is why Stroud Homes allows you to have your contract subject to the soil test result – just like a building & pest for an existing home.


How much is a soil test and how long does it take?

A soil test costs $800.00 and will also come with a contour survey and wind rating. Depending on the area, these generally take 21 days to process.

In some cases, the land developer sells the lots with the soil tests already completed. However, if this is not the case, Stroud Homes are able to arrange a soil test for you.

Unfortunately, you cannot use a soil test from a neighboring property, soil can change from block to block. Soil tests must be taken from the exact building pad to comply with Australian Standards.

There are many reasons why your soil test may differ from next door. Soil can be affected by any existing infrastructure, flora planted in the area, or previous land excavations.

If you want to know more about your soil type or need a Site Evaluation, contact the friendly team at Stroud Homes Toowoomba on 07 4615 4925 or send them a message below.

Your Local Builders
Megan Thomas
Megan Thomas

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