Residential construction on expansive soils

Abstract

Residences founded on expansive soils experience billions of dollars each year in damage caused by the heaving and shrinking of the foundation soils. It is thought that stiffening the foundation, while increasing the cost of the home, will save the homeowner from repair costs by reducing the percentage of homes in need of repair. This percentage is also known as the repair rate, Repair rates are developed by surveying-building permits for the city of College Station and estimating the number of repairs done by foundation contractors in the area. By developing repair rates and conducting surveys of local contractors determine the costs of repairs, it has been shown that there is an economical impetus to strengthen residential foundations if all the damage done to a home is considered. Based on damage to the foundation only, strengthening the foundation is not economically justified. Damage caused by expansive soils can be limited by using better construction techniques and foundation designs. Due to the competitiveness of the residential housing market, this can only be accomplished by improving the local building codes. Codes need to be improved in a comprehensive manner that covers site preparation, the actual design and construction of the residence, and the landscaping. Recommendations are also made for owner maintenance. An economic analysis and comparison is made between repair costs and improvements costs to show if improving the performance of a foundation is profitable or not. Data from a large foundation repair contractor in Dallas is compared to the information gathered from repair contractors operating in College Station. This comparison is used to predict costs of repairs based on the age of the foundation. The data are also compared to develop a probabilty of repair depending on the age of the foundation for the College Station area. Reviews of the current literature available on construction on expansive soils and repair techniques used to level residential foundations are included.