Ground slabs - Foundation movement
It is important to understand the effects of foundation movement on the slab. The slab must be designed and constructed to make sure that it is strong and stiff enough to oppose stresses. It is necessary to have a method of regulating the moisture content of the foundation soils so that the overall stress is minimised. Some of the ways in which this can be done are:
- appropriate drainage
- by sloping the ground away from the building
- paving
- careful tree planting
- minimal watering of garden beds.
The amount of water and its distribution throughout the soil have a direct influence on soil movement. Seasonal changes in the weather may cause overall expansion or shrinkage of the soil. Localised soil movement at a corner or along one side of a building may be caused by many factors.
Any of the following may cause localised variation in soil moisture:
- soil depressions, dams, bores
- natural water courses or springs, tidal areas
- leakage from water supply or drainage pipes
- pavements and driveways which drain water away from buildings
- septic tank drainage trenches
- excavation of soil which is subsequently replaced by another material with different soil characteristics
- heavily watered lawn and garden beds
- dense vegetation and trees.