19 counties mapped. On average, 29% of California county soil area is high shrink-swell clay (USDA SSURGO).
Foundation problems get more expensive the longer they wait. Get an assessment and repair quotes from independent local pros.
Get repair quotes →| County | Tier | High-risk % | Moderate % |
|---|---|---|---|
| Colusa | Severe | 53% | 18% |
| Solano | Severe | 51% | 16% |
| Yolo | Severe | 48% | 22% |
| Contra Costa | Severe | 46% | 21% |
| Sutter | Severe | 43% | 20% |
| Sacramento | Severe | 36% | 20% |
| Kings | Severe | 35% | 23% |
| Glenn | Severe | 34% | 18% |
| San Joaquin | Severe | 32% | 24% |
| Sonoma | High | 24% | 46% |
| Marin | High | 22% | 10% |
| Yuba | High | 22% | 34% |
| San Benito | High | 19% | 30% |
| Tehama | High | 17% | 24% |
| Orange County and Part of Riverside | High | 16% | 22% |
| Monterey | Moderate | 14% | 20% |
| Napa | Moderate | 13% | 35% |
| Santa Cruz | Moderate | 10% | 40% |
| Lake | Moderate | 9% | 27% |
Risk metrics are computed from USDA SSURGO soil survey data (linear extensibility of soil components, area-weighted by county). Soil varies lot to lot — this is county-scale context, not a substitute for a site-specific geotechnical or structural assessment.