New Zealand has an interesting and mixed geological history, which has resulted in a wide variety of soil types throughout the country, with different engineering characteristics. Some of our soils contain “active” clay minerals, which means that they are capable of swelling and shrinking, by taking in water or losing water. In New Zealand these types of soils are defined as “expansive” soils.
Expansive soils are not considered to be “good ground, as defined by NZS 3604:2011, New Zealand, Timber Framed Buildings (which is the New Zealand standard code of practice for the design of simple residential structures). Therefore, foundations founded on expansive soils require specific foundation design.
Shallow foundations, supported on expansive soils, which are not appropriately designed, can be adversely affected by the seasonal swelling and shrinkage of…
