Many hairline foundation cracks are usually considered to be caused by normal temperature expansions and contractions and the differential soil settlements and the movements of the dissimilar building component materials. If an inspection of the exposed exterior areas and the corresponding interior walls and ceilings reveals any visible evidence or damage that is normally associated with foundation failure, General Inspection will recommend that further analysis by a qualified foundation repair specialist or a structural engineer be performed before you purchase the home.
The normal settlement or the subsidence and consolidation process of the soils underlying the foundation slab may require up to 30 years to complete, with the majority of the consolidation generally occurring within the first few years. Depending upon the composition, the percentage of voids and the moisture content of the underlying soils, "settlement" may be "dormant", or still "active". Geo-technical (soil) investigations and analysis are required to accurately and completely make this determination, and are recommended should this be of a concern to the clients.
Settlement of your home is a natural occurance. Most lending institutions, architects and structural engineers use the general standard of settlement greater that 1" in 10' as an unacceptable degree of foundation settlement or point at which foundation failure has occurred. Keep in mind that most slab foundations are not finished at a perfectly level grade. There is no one correct way to build or to repair a house, so opinions may differ on the manner in which to or need to repair a foundation.
Foundation failure therefore becomes somewhat of a subjective conclusion based on the structural deflection and the experience of the individual observing the structure.
The Baton Rouge area is made up of primarily expansive clay soils that act like a sponge. As they absorb water, they swell and as they lose water they shrink. Soils tend to dry out (and shrink) during the summer and to absorb water (and swell) during the winter and spring.
As the soil under a house shrinks and swells with the seasons, the house and foundation will move up and down. As long as the foundation movement is not great enough to damage the house and/or foundation, most people do not consider the movement to be a foundation repair problem. If the up and down movement of a house foundation always returns the house foundation to its original level position, then damage to the house and foundation may appear and disappear on a regular basis as the seasons change.
If a homeowner wishes to stop seasonal house and foundation damage, the first course of action should be to follow a controlled watering program. By keeping the moisture content of the soil under the house foundation constant, foundation movement can often be stopped. This has been written to assist the homeowner in performing a simple foundation repair preventive maintenance program.
The goal of a foundation repair preventive maintenance watering program is to maintain a constant level of moisture in the soil under the house and foundation. The best way to water a foundation is to place a soaker hose from one to two feet from the edge of the foundation. Placing the hose a short distance from the foundation allows the water to soak into the soil evenly.
The hose should not be placed against the foundation. When soil has dried and cracked, water can travel along the cracks for several feet in all directions. If the soil around your foundation is dried and cracked, then water placed next to the foundation will run through the cracks and accumulate at the bottom of the grade beam (the thick portion of the foundation that is under the exterior walls). In some cases, an accumulation of water in the soil at the base of a foundation can cause the soil to lose some of its load-bearing capacity. If the soil loses enough load-bearing capacity, the house will sink into the ground.
Obviously, it is necessary to water more during hot, dry weather and less during cold, damp weather. The amount of water required to keep a foundation stable during the summer can be surprisingly large. A single large tree can remove as much as 150 gallons of water, or almost 20 cubic feet of water, from the soil each day. Shrubs and other plants can also remove large quantities of water. During persistent hot dry weather, it may be necessary to water a foundation daily. Watering should supply enough water to keep the moisture content in the soil under the foundation constant. If the amount of water applied is only enough to keep the surface damp, the watering program will not work. Obviously, the homeowner is the only one who can weigh the benefits of controlling foundation movement versus the increased size of the water bill.