Foundation problems associated with expansive clay are usually caused by the lack of moisture in the soil, which shrinks when dry and result in foundation deflections and settlements. When the moisture content of the active supporting soil at a perimeter of the foundation is maintained uniformly, the chances of foundation failure are greatly alleviated.
Before any foundation maintenance can be effectively implemented, it is imperative that proper drainage is provided. That could necessitate some recontouring of existing grade, placing fill dirt at perimeter grade beams, placing splash blocks at downspouts to prevent soil erosion and other specifics peculiar to a particular site. Water should always run away from the house and there should be no pounding water near the foundation. Care should be taken to insure that soil is from one to two inches below the top of the perimeter grade beams. The soil should be sloped approximately one inch per foot to drain at least eighteen inches from the perimeter of the foundation.
The moisture content of the soil at the perimeter of the foundation should slowly be increased and maintained during all seasons. This is best accomplished by placing soaker hoses eighteen inches from the foundation and regulated to a flow of one-fourth inch in height until water is observed standing on the ground. The volumetric expansion of the active soil will now provide uniform support for the foundation. Watering should be repeated when drying cracks are observed when the soil is evidently dry.
Trees and shrubbery can produce an adverse effect on the foundation. Their roots sap moisture from the soil; both at the perimeter and under the slab. This lowers moisture content of the active supporting soil at various places, which causes differential movements of the foundation. In certain instances, root severing of the foundation may be recommended.
Guttering is not necessary where proper drainage is provided. On gabled ends or sides of the house, there is no run-off so more watering will probably be required. During hot and dry seasons, the South and West side may require more watering than the North and East sides, which are shaded and not exposed to as much direct sun.
Most major foundation movements can be prevented if the active supporting soil is well maintained. The extent of distress transmitted to the structure would be lessened and the service life of the residence would be considerably increased.