Idaho: basement moisture and foundation risk by county
44 counties, ranked by our combined index. Highest combined risk is Bonner County (35), lowest is Nez Perce County (22). The worst soil for foundation cracks specifically is in Clark County.
| County | Index | Moisture | Cracks | Water table | Region |
|---|---|---|---|---|---|
| Bonner County | 35 | 29 | 34 | 46 | Rocky Mountains |
| Clark County | 35 | 31 | 43 | 30 | Snake River Plain |
| Bear Lake County | 34 | 32 | 39 | 30 | Snake River Plain |
| Benewah County | 34 | 30 | 41 | 30 | Rocky Mountains |
| Oneida County | 34 | 34 | 38 | 30 | Snake River Plain |
| Washington County | 34 | 33 | 37 | 30 | Snake River Plain |
| Canyon County | 33 | 31 | 38 | 30 | Snake River Plain |
| Cassia County | 33 | 32 | 36 | 30 | Snake River Plain |
| Clearwater County | 33 | 30 | 39 | 30 | Rocky Mountains |
| Franklin County | 33 | 30 | 38 | 30 | Snake River Plain |
| Fremont County | 33 | 34 | 33 | 30 | Snake River Plain |
| Boundary County | 32 | 28 | 39 | 30 | Rocky Mountains |
| Gem County | 32 | 32 | 34 | 30 | Snake River Plain |
| Gooding County | 32 | 31 | 35 | 30 | Snake River Plain |
| Payette County | 32 | 32 | 34 | 30 | Snake River Plain |
| Caribou County | 31 | 30 | 34 | 30 | Snake River Plain |
| Power County | 31 | 33 | 28 | 30 | Snake River Plain |
| Teton County | 31 | 33 | 28 | 30 | Snake River Plain |
| Adams County | 30 | 29 | 20 | 46 | Rocky Mountains |
| Bannock County | 30 | 34 | 25 | 30 | Snake River Plain |
| Bingham County | 30 | 33 | 27 | 30 | Snake River Plain |
| Camas County | 30 | 33 | 37 | 16 | Snake River Plain |
| Custer County | 30 | 34 | 25 | 30 | Snake River Plain |
| Elmore County | 30 | 31 | 30 | 30 | Snake River Plain |
| Jefferson County | 30 | 31 | 30 | 30 | Snake River Plain |
| Lemhi County | 30 | 28 | 34 | 30 | Rocky Mountains |
| Minidoka County | 30 | 30 | 29 | 30 | Snake River Plain |
| Owyhee County | 30 | 30 | 29 | 30 | Snake River Plain |
| Ada County | 29 | 32 | 35 | 16 | Snake River Plain |
| Idaho County | 29 | 29 | 39 | 16 | Rocky Mountains |
| Lincoln County | 29 | 31 | 26 | 30 | Snake River Plain |
| Shoshone County | 29 | 30 | 27 | 30 | Rocky Mountains |
| Valley County | 29 | 28 | 17 | 46 | Rocky Mountains |
| Jerome County | 28 | 33 | 20 | 30 | Snake River Plain |
| Lewis County | 28 | 28 | 36 | 16 | Rocky Mountains |
| Twin Falls County | 28 | 30 | 24 | 30 | Snake River Plain |
| Blaine County | 27 | 30 | 21 | 30 | Snake River Plain |
| Bonneville County | 27 | 31 | 28 | 16 | Snake River Plain |
| Butte County | 27 | 33 | 26 | 16 | Snake River Plain |
| Kootenai County | 27 | 31 | 20 | 30 | Rocky Mountains |
| Madison County | 27 | 32 | 19 | 30 | Snake River Plain |
| Latah County | 25 | 29 | 25 | 16 | Rocky Mountains |
| Boise County | 24 | 33 | 18 | 16 | Snake River Plain |
| Nez Perce County | 22 | 28 | 18 | 16 | Rocky Mountains |
Values from USDA NRCS SSURGO where available, otherwise our regional model — each county page states which. Methodology.
The physiographic regions inside Idaho
State lines are political; soil follows geology. These are the distinct ground types inside Idaho and why each behaves the way it does.
Snake River Plain
Basalt sits just below a loess cap. Excavating for a basement is expensive, and where one exists it often bears directly on rock — which does not move, but does not let water through either.
31 counties: Ada County, Bannock County, Bear Lake County, Bingham County, Blaine County, Boise County, Bonneville County, Butte County, Camas County, Canyon County, Caribou County, Cassia County, Clark County, Custer County, Elmore County, Franklin County, Fremont County, Gem County, Gooding County, Jefferson County, Jerome County, Lincoln County, Madison County, Minidoka County, Oneida County, Owyhee County, Payette County, Power County, Teton County, Twin Falls County, Washington County
Rocky Mountains
Shallow bedrock and coarse material. Basements are shallow or absent, and the problem is spring meltwater rather than a water table.
13 counties: Adams County, Benewah County, Bonner County, Boundary County, Clearwater County, Idaho County, Kootenai County, Latah County, Lemhi County, Lewis County, Nez Perce County, Shoshone County, Valley County
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