The American Society of Civil Engineers estimates that one quarter of all homes in the United States have some damage caused by expansive soils. In a typical year in the United States they cause a greater financial loss to property owners than earthquakes, floods, hurricanes and tornadoes combined.
State building codes provide general guidelines, minimum footing requirements and presumptive soil-bearing values for various soil types, bearing capacities, material requirements and estimated lateral loads. But a building code cannot accurately predict your building project’s specific needs. Savvy builders in Texas understand that with subsurface soil conditions ranging from solid rock to highly expansive clays (oftentimes in the same community), construction can be high-stakes and expensive if not handled correctly. A structural engineer’s stamp of approval on a foundation plan is the only way to assure foundation integrity.
An engineered foundation is defined as one for which design is based on three phases:
- Geotechnical Engineering Information
Load conditions are very “area specific.” The Texas State Historical Association’s division of land resources recognizes over 1,300 different types of soil in our state, each with its own distinct attributes and characteristics.
It is important that your structural engineer is familiar with your area’s weather conditions and soil types because every soil has a unique capacity to bear the intensity of a load per unit area. For example, sand or gravel may have a bearing capacity of 3000-4000psf (lbs/sq/ft) while clay only has a support capacity of around 1500psf. The higher the bearing capacity of a soil, the smaller the footing you need.
Soil testing is also essential in assuring a foundation’s essential role to act as a barrier keeping water from penetrating the living space. Certain soils, specifically clay-like soils prevalent in many areas of Texas, expand and contract more rapidly when exposed to moisture.