Dealing with subsidence
Subsidence is the excessive movement of the ground supporting a building. If this movement varies from one part of a building to another, cracks may occur.
Causes of subsidence include:
- soil compressing under the weight of the house
- soil swelling and contracting due to changes in the moisture content.
Subsidence and footing design
In Queensland, engineers design footings to the Australian Standard AS2870 – 2011 Residential slabs and footings. Footing design and construction involves a number of steps:
- site classification
- selecting the footing system
- structural design
- building in accordance with the required design details and methods
- proper maintenance.
Choosing appropriate site falls and floor levels should be part of the planning and setting out process during the construction of a new home or renovation. Advice from a qualified Registered Professional Engineer about the installation of an appropriate footing system is essential prior to building your home. Either you or your builder can source this advice.
- Maintain site drainage
- altering the site drainage provided by the builder. Any drainage changes should direct water away from your house and adjoining properties
- placing gardens, garden edging or gravel pavements next to your house. These can cause water retention or may change the moisture conditions, particularly on reactive clay sites
- installing a sprinkler system next to your house if it is on a highly and extremely reactive site
- over watering.
- Plant trees around your house at a distance greater than the fully-grown height of the tree
- Regularly check and maintain plumbing, drainage and stormwater systems. Immediately repair leaks as well as minor damage and cracking in walls and ceilings.