Limitations of Residential Structures on Expansive Soils

Failures due to expansive soils tie with hurricanes for second place among America's most destructive hazards in terms of economic loss to buildings. This paper discusses the limitations of conventional design, construction, and repair of residential structures. Two specific case studies are presented. The first addresses excessive movement and damage at several posttensioned slab-on-ground condominium buildings. The second discusses severe vertical and horizontal deformation of a tract home supported by a drilled pier foundation system. Remedial recommendations for each case study are discussed along with lessons learned from each. Damages and movement that initially indicate upward movement may actually be caused by settlement even in an area of extremely expansive soils. The unique situation of each type of residence often requires the decision of which path to take during repair; that is, one of providing additional flexibility or rigidity. This type of decision-making process should also be considered during the initial design construction phase.