Foundation Information: Shrinking Soil,
 & Poor Drainage Cause Damage.

That small crack in your foundation, brick wall or concrete floor has deeper consequences and is the subject of major economic concern in the U.S. More than one person in five is, or will be, affected economically by structural damage. By comparison, fewer than one in ten is affected by flood or earthquake. Homes built on shrinking or swelling soils have up to a 60 percent chance of damage from this little known, and even less understood, natural occurrence.
Structural damage ranks as the second most-likely natural cause of economic loss (insect damage is first). Estimates prepared by the Federal Housing Administration approach $20 billion annually.

What can a homeowner do?

Trace visible signs of settling or structural movement to its source. Here are a few signs to watch for:

•Doors and windows open and shut with difficulty.
•Caulking cracks and pulls loose around windows and doors.
•Concrete floors crack, tilt and move.

The problem should be tackled while in its early stages. Once the structural unity of the building is broken, continued movement can affect more of the structure.

Many, methods are used to stabilize a building structure that has failed. Underpinning the foundation is the most effective. The system of shallow excavation and pouring concrete pads and piers is effective, but can fail in the long term. This method almost never reaches the depth necessary to connect with a strata of sufficient bearing quality. In addition, traditional methods can be costly in terms of time and the effect of disturbance of lawns, landscaping and other areas.
The most effective method is to underpin the structure with steel piering, which is

driven to a sufficient depth to support the calculated load. This remedy tends to be permanent and, on some applications, can be adjusted later if necessary. This system also can be installed more quickly, and with less site disturbance.

Discussion of Cause and Effect of Structural Failure in Residential and Lightly
 Loaded Commercial Structures. 

1. Lack of uniformity in soil compaction beneath structural elements.
2. Settling due to unequal loads at different foundation locations.
3. Different soil composition, or fill materials, at load bearing locations of structure, and/or structural components.
4. Moisture content of clays or other soils with a high plasticity index, capable of significant changes in mass through the process of expansion and contraction, i.e. movement.
5. Poor or inadequate design, in size or strength of foundations, contractor failure in following specifications or "cutting corners" through omitting reinforcing steel, or use of inferior concrete grades, construction during periods of weather conditions which properly should preclude the pouring of concrete, or use of masonry grouts, and the countless other human errors which can result in faulty or poorly performed construction.
6. Drainage problems, both of sub-surface flow, and ground water affecting the soil condition at locations which have a causal relationship with the integrity of the bearing characteristics of structural elements.
7. Exposure to direct sunlight in locations which, with extremes of soil or grade deficiencies, "can cause excessive drying and resultant shrinkage of soil mass to the point where the loading pressures can cause a failure in bearing components.
8. Erosion of soils, required for the continuing integrity of the structure.
9. Planting of trees, shrubs and other vegetation which can contribute to any of the above conditions.
10. Concrete floors, particularly of the "slab on grade" type which can be affected by any of the above conditions, and which are, in most instances, poured without any steel mesh or reinforcing, resulting in a low tensile strength, highly potential to break, crack or tilt, as a result of any combination of the above conditions. (Back to Top)