Montana: basement moisture and foundation risk by county
56 counties, ranked by our combined index. Highest combined risk is Custer County (56), lowest is Ravalli County (23). The worst soil for foundation cracks specifically is in Custer County.
| County | Index | Moisture | Cracks | Water table | Region |
|---|---|---|---|---|---|
| Custer County | 56 | 39 | 100 | 30 | Missouri Plateau (unglaciated Great Plains) |
| Pondera County | 55 | 37 | 98 | 30 | Missouri Plateau (unglaciated Great Plains) |
| Sweet Grass County | 55 | 39 | 95 | 30 | Missouri Plateau (unglaciated Great Plains) |
| Park County | 54 | 41 | 89 | 30 | Missouri Plateau (unglaciated Great Plains) |
| Daniels County | 53 | 38 | 91 | 30 | Missouri Plateau (unglaciated Great Plains) |
| Powder River County | 53 | 38 | 100 | 16 | Missouri Plateau (unglaciated Great Plains) |
| Treasure County | 53 | 39 | 88 | 30 | Missouri Plateau (unglaciated Great Plains) |
| Judith Basin County | 52 | 39 | 85 | 30 | Missouri Plateau (unglaciated Great Plains) |
| Wheatland County | 52 | 40 | 94 | 16 | Missouri Plateau (unglaciated Great Plains) |
| Fallon County | 51 | 38 | 85 | 30 | Missouri Plateau (unglaciated Great Plains) |
| Hill County | 51 | 38 | 85 | 30 | Missouri Plateau (unglaciated Great Plains) |
| Toole County | 51 | 41 | 91 | 16 | Missouri Plateau (unglaciated Great Plains) |
| Fergus County | 50 | 42 | 75 | 30 | Missouri Plateau (unglaciated Great Plains) |
| Garfield County | 50 | 39 | 81 | 30 | Missouri Plateau (unglaciated Great Plains) |
| Big Horn County | 49 | 41 | 84 | 16 | Missouri Plateau (unglaciated Great Plains) |
| Dawson County | 49 | 42 | 71 | 30 | Missouri Plateau (unglaciated Great Plains) |
| McCone County | 49 | 39 | 86 | 16 | Missouri Plateau (unglaciated Great Plains) |
| Musselshell County | 49 | 42 | 84 | 16 | Missouri Plateau (unglaciated Great Plains) |
| Carbon County | 48 | 41 | 80 | 16 | Missouri Plateau (unglaciated Great Plains) |
| Chouteau County | 48 | 39 | 75 | 30 | Missouri Plateau (unglaciated Great Plains) |
| Liberty County | 48 | 42 | 80 | 16 | Missouri Plateau (unglaciated Great Plains) |
| Wibaux County | 48 | 37 | 88 | 16 | Missouri Plateau (unglaciated Great Plains) |
| Yellowstone County | 48 | 39 | 73 | 30 | Missouri Plateau (unglaciated Great Plains) |
| Carter County | 47 | 40 | 69 | 30 | Missouri Plateau (unglaciated Great Plains) |
| Valley County | 46 | 37 | 80 | 16 | Missouri Plateau (unglaciated Great Plains) |
| Blaine County | 45 | 37 | 68 | 30 | Missouri Plateau (unglaciated Great Plains) |
| Prairie County | 45 | 42 | 60 | 30 | Missouri Plateau (unglaciated Great Plains) |
| Teton County | 45 | 41 | 60 | 30 | Missouri Plateau (unglaciated Great Plains) |
| Phillips County | 44 | 38 | 61 | 30 | Missouri Plateau (unglaciated Great Plains) |
| Roosevelt County | 44 | 40 | 61 | 30 | Missouri Plateau (unglaciated Great Plains) |
| Rosebud County | 44 | 40 | 71 | 16 | Missouri Plateau (unglaciated Great Plains) |
| Stillwater County | 44 | 40 | 59 | 30 | Missouri Plateau (unglaciated Great Plains) |
| Golden Valley County | 43 | 40 | 58 | 30 | Missouri Plateau (unglaciated Great Plains) |
| Petroleum County | 43 | 41 | 64 | 16 | Missouri Plateau (unglaciated Great Plains) |
| Richland County | 42 | 37 | 57 | 30 | Missouri Plateau (unglaciated Great Plains) |
| Sheridan County | 40 | 40 | 58 | 16 | Missouri Plateau (unglaciated Great Plains) |
| Cascade County | 39 | 37 | 57 | 16 | Missouri Plateau (unglaciated Great Plains) |
| Deer Lodge County | 35 | 29 | 34 | 46 | Rocky Mountains |
| Sanders County | 35 | 32 | 31 | 46 | Rocky Mountains |
| Flathead County | 34 | 30 | 31 | 46 | Rocky Mountains |
| Beaverhead County | 33 | 30 | 38 | 30 | Rocky Mountains |
| Glacier County | 32 | 30 | 35 | 30 | Rocky Mountains |
| Granite County | 30 | 30 | 17 | 46 | Rocky Mountains |
| Lake County | 30 | 31 | 40 | 16 | Rocky Mountains |
| Meagher County | 30 | 30 | 20 | 46 | Rocky Mountains |
| Powell County | 30 | 30 | 19 | 46 | Rocky Mountains |
| Broadwater County | 29 | 29 | 16 | 46 | Rocky Mountains |
| Madison County | 29 | 31 | 14 | 46 | Rocky Mountains |
| Gallatin County | 28 | 29 | 34 | 16 | Rocky Mountains |
| Lewis and Clark County | 27 | 30 | 21 | 30 | Rocky Mountains |
| Lincoln County | 27 | 30 | 20 | 30 | Rocky Mountains |
| Jefferson County | 26 | 28 | 21 | 30 | Rocky Mountains |
| Silver Bow County | 26 | 30 | 19 | 30 | Rocky Mountains |
| Mineral County | 25 | 29 | 17 | 30 | Rocky Mountains |
| Missoula County | 25 | 29 | 25 | 16 | Rocky Mountains |
| Ravalli County | 23 | 28 | 22 | 16 | Rocky Mountains |
Values from USDA NRCS SSURGO where available, otherwise our regional model — each county page states which. Methodology.
The physiographic regions inside Montana
State lines are political; soil follows geology. These are the distinct ground types inside Montana and why each behaves the way it does.
Missouri Plateau (unglaciated Great Plains)
The water table is deep, so basements rarely flood — but Pierre Shale is one of the most expansive substrates in North America. The risk here is mechanical, not hydraulic.
37 counties: Big Horn County, Blaine County, Carbon County, Carter County, Cascade County, Chouteau County, Custer County, Daniels County, Dawson County, Fallon County, Fergus County, Garfield County, Golden Valley County, Hill County, Judith Basin County, Liberty County, McCone County, Musselshell County, Park County, Petroleum County, Phillips County, Pondera County, Powder River County, Prairie County, Richland County, Roosevelt County, Rosebud County, Sheridan County, Stillwater County, Sweet Grass County, Teton County, Toole County, Treasure County, Valley County, Wheatland County, Wibaux County, Yellowstone County
Rocky Mountains
Shallow bedrock and coarse material. Basements are shallow or absent, and the problem is spring meltwater rather than a water table.
19 counties: Beaverhead County, Broadwater County, Deer Lodge County, Flathead County, Gallatin County, Glacier County, Granite County, Jefferson County, Lake County, Lewis and Clark County, Lincoln County, Madison County, Meagher County, Mineral County, Missoula County, Powell County, Ravalli County, Sanders County, Silver Bow County
Page data updated