Settlement, Heave & Tree Effect

A building site's soil condition and make-up is determined to give each site a classification. It is this classification, along with other data, that is used by engineers to design the appropriate footing system for the structure to be built.

(Click here to see the latest soil classification table: AS 2870 Changes)

Most soils change in volume to a varying degree based upon their ability to absorb to moisture. They increase in volume upon wetting and decrease when dried out.

Each year in Australia, some 50,000 houses experience some form of cracking or structural damage. This accounts for about 80% of all housing insurance claims, and most often soil movement is the cause.


       Soil Movement caused by the elements     Soil movement caused by human intervention

If a homeowner plants trees near their house, the soil will shrink due to the tree seeking water, and therefore moisture is extracted from the foundation soil. As the house settles, brick walls crack, timber frames distort and doors jam.

Should a home owner water their beloved gardens excessively, or ignore broken drains and pipes, the soil will heave. This movement too can result in cracking walls and timber frame distortion.


 Examples of the potential damage caused by moving foundations


All of this damage can be significantly reduced or even eliminated by using a PolyVoid designed concrete slab where the Polyvoid design and construction and compliance processes are followed.

Click here to learn more: PolyVoid for the Industry