By Matthew Power. "We have always known that soils in Southern Nevada are extremely challenging," says Klif Andrews, vice president of community development for Pardee Homes in Las Vegas. "They are highly expansive, with high sulfates in some areas."
Geotechnical engineer Greg DeSart of Geotechnical & Environmental Services in Las Vegas says that legal pressure is driving up home costs, because builders--and engineers--now tend to do extra work on soils and foundations, just to be safe. "We might call for deeper excavation, or foundation designs may be thicker with more reinforcement. A lot of it is probably unnecessary."
Andrews points out that "the problems you see are more common in flatwork (such as walkways and driveways) than foundations--as you might expect." He adds that one of the worst soils to deal with is also the hardest to identify: hydro collapsible soil. You don't know they're there until you add water. Then, they simply collapse and leave a hole."
Andrews says that most problems in the region occur because a builder may find acceptable soils at one part of a site, when another spot 50 feet away could contain expansive clay--leading to an inadequate foundation design.