22 counties mapped. On average, 10% of Idaho county soil area is high shrink-swell clay (USDA SSURGO).
Higher percentages mean more of a county's mapped soil is shrink-swell clay that expands and contracts with moisture. This is county-scale exposure, not a diagnosis of any single home — but it tells you whether soil movement belongs on your radar.
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Before you call a foundation company →| County | Tier | High-risk % | Moderate % |
|---|---|---|---|
| Franklin | High | 29% | 28% |
| Owyhee | High | 27% | 51% |
| Gem | High | 24% | 28% |
| Jefferson | High | 23% | 16% |
| Blaine | High | 21% | 33% |
| Camas | High | 20% | 48% |
| Ada | High | 20% | 43% |
| Idaho | High | 18% | 32% |
| Latah | Moderate | 6% | 54% |
| Bear Lake | Moderate | 6% | 37% |
| Oneida | Low | 5% | 40% |
| Boise | Low | 4% | 10% |
| Payette | Low | 4% | 48% |
| Caribou | Low | 4% | 25% |
| Bonneville | Low | 4% | 13% |
| Boundary | Low | 3% | 11% |
| Kootenai | Low | 3% | 14% |
| Benewah | Low | 3% | 24% |
| Cassia | Low | 2% | 21% |
| Fremont | Low | 2% | 19% |
| Power | Low | 0% | 10% |
| Madison | Low | 0% | 19% |
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.