“We’ve seen a tremendous influx of pretty severe cases due to either drought or too much rain,” said Dan Jaggers, vice president of technical services at Olshan Foundation Repair, which has offices in the South, Midwest and Great Plains. “People call panicked because they’ve got gaping cracks in their walls, tile breaking, grout popping and they don’t know what to do.” Other telltale signs of foundation failure include doors and windows that will not close, chimneys or porches separating from the house and bowing basement walls.

After a particularly dry summer followed by deluges in the fall, Psonya Wilson, a lawyer in Brandon, Miss., noticed light streaming in where the wall had separated from the baseboard in the bedroom of her 5-year-old son. “I could stick my finger through it,” she said. “I couldn’t believe it. The whole back part of the house had sunk about six inches.” To stop further collapse, not to mention to control the draft, she is having several stabilization piers installed to shore up the foundation of her two-story garden style house; it will cost more than $5,000.

Data from the National Oceanic and Atmospheric Association indicates that since the 1990s there has been an accelerating trend nationwide toward more extended dry periods followed by downpours. Whether due to random climate patterns or global warming, the swings between hot and dry weather and severe rain or snow have profoundly affected soil underneath buildings.

Clay soils, like those beneath the houses of Mr. Derse and Ms. Wilson, shrink during droughts and swell during floods, causing structures to bob. And because sandier soil loses its adhesive properties in dry conditions, it pulls away from foundations. Heavy rains cause it to shift or just collapse beneath structures. With both kinds of soil, such sinking, called subsidence, usually happens gradually, said Randall Orndorff, a geologist with the United States Geologic Survey. But, he said, “swinging from very wet to extremely dry weather like we’ve been seeing lately in many parts of the country may be accelerating the effect.”

Experts estimate the cost to homeowners to stabilize or shore up foundations is around $4 billion annually, up from $3 billion 10 years ago, although more houses have also been built in that time period. Subsidence is not covered by most homeowners’ insurance policies in the United States, unlike in Britain, where the increasing number of homeowners’ claims due to foundation failure prompted the Charter Insurance Institute, an industry trade group, to issue a dire warning about the financial drain in its 2009 report, “Coping with Climate Change: Risks and Opportunities for Insurers.”