Cracks and damage to walls and foundations are caused primarily by soils that contract and expand due to moisture content. The soil absorbs water and swells up and then shrinks when it dries out. This puts pressure on foundations, and if not designed and built correctly, will lead to walls cracking and even collapsing. Other soil types, dolomite for instance, can dissolve in water during heavy rains or when drainpipes and water pipes leak.
All soils are affected by water. Water can weaken the structure of some soils causing gradual or sudden settlements (or collapse) to take place. Expansive soils shrink or swell in response to changes in moisture content, resulting in heave movements. The owner should therefore:
- Pay attention to drainage of the site. Storm water and garden irrigation water should not be permitted to pond within 1,5 m of foundations and walls.
- Ensure that shrubs are not planted too close to foundations and walls. The regulations specify a minimum distance of 1,2 m for expansive soil sites, and 1,5 m for compressible and potentially collapsible soil sites.
- Ensure the prompt repair of leaks in all plumbing and drainage, as this will cause catastrophic failure in the foundation.
Trees that can cause damage
Many foundations are likely to be located in close proximity to planted or self-sown trees during their useful life. In some situations, trees can adversely affect foundations and induce damage.
All trees should be regarded as a potential source of damage. The following varieties are, however, particularly prone to causing damage:
- All eucalyptus varieties
- Lombardy (Free State) poplars
- London planes
- Willows (Salix) of any type Jacarandas
REMEMBER: Your home foundation is exactly what it means.