HouseCheck home inspectors frequently encounter poor ground water management when inspecting houses. This includes bad management of rain water from the roof and also incorrect ground levels and grading of the property. Gerrie van Niekerk, Operations Director of HouseCheck points out that erf grading and drainage can have a significant negative impact on the building structure.
Common damage caused by poor storm water management, which is regularly documented in HouseCheck home inspection reports, includes foundation subsidence and wall cracks. Foundation settlement is frequently seen in houses where downpipes discharge on unprotected soil at the base of walls.
Incorrect grading and ground levels which results in ponding of water against the walls often results, not only in foundation settlement, but also in damp damage to the structure. The finished ground level around a house should be at least 150mm lower than the finished floor level of the house. The picture shows a house where the ground level is higher than the floor level and flooding of the interior is almost a given.
Given the fact that most of South African housing is built in areas with problem soils, poor foundation design very often exacerbates the problems caused by poor ground water management. To cut costs, builders often skimp on foundations and, due to a lack of adequate engineering supervision, often neglect to install steel reinforcement in the concrete foundation footings in problem soil areas.
Van Niekerk says it is very important that:
- The foundations of a house should be strong enough to cope with expected movement caused by soil conditions in the area in which the house is built.
- Runoff water from the roof should always be adequately diverted away from the house by means of a good drainage system.
- The property should also be graded so that the ground slopes away from the structure around the perimeter of the building.
- The installation of a properly sloped impervious apron (concrete or paving) around the base of the house walls is also prudent.