Structural cracking in Australian homes is expected to increase between 5% and 10% in the next twelve months. Australia's soils will continue to dry out with the onset of summer, placing further strain on buildings.
The causes of foundation movement are often similar and fit into five categories;
Reactive Clay This is by far the most common cause of the cracks. Reactive clay is often referred to as plastic clay and shrinks when it is dry and swells when it is wet. Footings sitting on reactive clay move up and down when the foundation material (soil/clay) swells and shrinks.
Broken water pipes The damage caused by broken service pipes looks just like cracks caused by reactive clay. They are usually more common on internal walls. These cracks continue to spread until the pipe is fixed. A period of equalisation of the moisture content in the soil may be required to allow for the foundation to stabilise
Undermining by Trenches This type of movement is usually significant and generally localised to excavation of trench areas, cracking will continue until foundations are underpinned.
Footings founded in fill House footings can be founded in properly engineered fill platforms. This is can be very effective if done properly. When done without adequate advice, footings founded in poor fill will settle and cause cracking until the fill is compressed under its own weight.
Poor control jointing Control joints will often reduce cracking caused by poor footing design. They are an effective way to control cracking that can be caused by reactive clays. All brick walls should be jointed.
As a Pre-Purchase Inspector we identify defects in the property and make recommendations that enable the purchaser to make an informed decision about whether to buy the property. In relation to cracking, if the information is not available to properly assess the significance of the cracks then the purchaser is informed of what steps to take in order to obtain that advice, which maybe the recommendation of a Structural Engineer.
Reactive Clay
