BasementSoil

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.

Where in Montana the ground is worse

Every county in the state, coloured by the soil values below. Click a county to open its report; switch what the colour means with the buttons. The pattern is geology, not administration — risk stops at the edge of a physiographic region, not at a county line.

Beaverhead County, MT — combined 33/100, moisture 30, movement 38, water table 30Big Horn County, MT — combined 49/100, moisture 41, movement 84, water table 16Blaine County, MT — combined 45/100, moisture 37, movement 68, water table 30Broadwater County, MT — combined 29/100, moisture 29, movement 16, water table 46Carbon County, MT — combined 48/100, moisture 41, movement 80, water table 16Carter County, MT — combined 47/100, moisture 40, movement 69, water table 30Cascade County, MT — combined 39/100, moisture 37, movement 57, water table 16Chouteau County, MT — combined 48/100, moisture 39, movement 75, water table 30Custer County, MT — combined 56/100, moisture 39, movement 100, water table 30Daniels County, MT — combined 53/100, moisture 38, movement 91, water table 30Dawson County, MT — combined 49/100, moisture 42, movement 71, water table 30Deer Lodge County, MT — combined 35/100, moisture 29, movement 34, water table 46Fallon County, MT — combined 51/100, moisture 38, movement 85, water table 30Fergus County, MT — combined 50/100, moisture 42, movement 75, water table 30Flathead County, MT — combined 34/100, moisture 30, movement 31, water table 46Gallatin County, MT — combined 28/100, moisture 29, movement 34, water table 16Garfield County, MT — combined 50/100, moisture 39, movement 81, water table 30Glacier County, MT — combined 32/100, moisture 30, movement 35, water table 30Golden Valley County, MT — combined 43/100, moisture 40, movement 58, water table 30Granite County, MT — combined 30/100, moisture 30, movement 17, water table 46Hill County, MT — combined 51/100, moisture 38, movement 85, water table 30Jefferson County, MT — combined 26/100, moisture 28, movement 21, water table 30Judith Basin County, MT — combined 52/100, moisture 39, movement 85, water table 30Lake County, MT — combined 30/100, moisture 31, movement 40, water table 16Lewis and Clark County, MT — combined 27/100, moisture 30, movement 21, water table 30Liberty County, MT — combined 48/100, moisture 42, movement 80, water table 16Lincoln County, MT — combined 27/100, moisture 30, movement 20, water table 30Madison County, MT — combined 29/100, moisture 31, movement 14, water table 46McCone County, MT — combined 49/100, moisture 39, movement 86, water table 16Meagher County, MT — combined 30/100, moisture 30, movement 20, water table 46Mineral County, MT — combined 25/100, moisture 29, movement 17, water table 30Missoula County, MT — combined 25/100, moisture 29, movement 25, water table 16Musselshell County, MT — combined 49/100, moisture 42, movement 84, water table 16Park County, MT — combined 54/100, moisture 41, movement 89, water table 30Petroleum County, MT — combined 43/100, moisture 41, movement 64, water table 16Phillips County, MT — combined 44/100, moisture 38, movement 61, water table 30Pondera County, MT — combined 55/100, moisture 37, movement 98, water table 30Powder River County, MT — combined 53/100, moisture 38, movement 100, water table 16Powell County, MT — combined 30/100, moisture 30, movement 19, water table 46Prairie County, MT — combined 45/100, moisture 42, movement 60, water table 30Ravalli County, MT — combined 23/100, moisture 28, movement 22, water table 16Richland County, MT — combined 42/100, moisture 37, movement 57, water table 30Roosevelt County, MT — combined 44/100, moisture 40, movement 61, water table 30Rosebud County, MT — combined 44/100, moisture 40, movement 71, water table 16Sanders County, MT — combined 35/100, moisture 32, movement 31, water table 46Sheridan County, MT — combined 40/100, moisture 40, movement 58, water table 16Silver Bow County, MT — combined 26/100, moisture 30, movement 19, water table 30Stillwater County, MT — combined 44/100, moisture 40, movement 59, water table 30Sweet Grass County, MT — combined 55/100, moisture 39, movement 95, water table 30Teton County, MT — combined 45/100, moisture 41, movement 60, water table 30Toole County, MT — combined 51/100, moisture 41, movement 91, water table 16Treasure County, MT — combined 53/100, moisture 39, movement 88, water table 30Valley County, MT — combined 46/100, moisture 37, movement 80, water table 16Wheatland County, MT — combined 52/100, moisture 40, movement 94, water table 16Wibaux County, MT — combined 48/100, moisture 37, movement 88, water table 16Yellowstone County, MT — combined 48/100, moisture 39, movement 73, water table 30
  • Low (0–27)
  • Moderate (28–49)
  • Elevated (50–74)
  • High (75–100)

County boundaries: US Census TIGER (public domain), simplified for display. Colours are our index from USDA SSURGO fields where loaded, otherwise from our regional model — each county page states which. How the index is calculated.

CountyIndexMoistureCracksWater tableRegion
Custer County563910030Missouri Plateau (unglaciated Great Plains)
Pondera County55379830Missouri Plateau (unglaciated Great Plains)
Sweet Grass County55399530Missouri Plateau (unglaciated Great Plains)
Park County54418930Missouri Plateau (unglaciated Great Plains)
Daniels County53389130Missouri Plateau (unglaciated Great Plains)
Powder River County533810016Missouri Plateau (unglaciated Great Plains)
Treasure County53398830Missouri Plateau (unglaciated Great Plains)
Judith Basin County52398530Missouri Plateau (unglaciated Great Plains)
Wheatland County52409416Missouri Plateau (unglaciated Great Plains)
Fallon County51388530Missouri Plateau (unglaciated Great Plains)
Hill County51388530Missouri Plateau (unglaciated Great Plains)
Toole County51419116Missouri Plateau (unglaciated Great Plains)
Fergus County50427530Missouri Plateau (unglaciated Great Plains)
Garfield County50398130Missouri Plateau (unglaciated Great Plains)
Big Horn County49418416Missouri Plateau (unglaciated Great Plains)
Dawson County49427130Missouri Plateau (unglaciated Great Plains)
McCone County49398616Missouri Plateau (unglaciated Great Plains)
Musselshell County49428416Missouri Plateau (unglaciated Great Plains)
Carbon County48418016Missouri Plateau (unglaciated Great Plains)
Chouteau County48397530Missouri Plateau (unglaciated Great Plains)
Liberty County48428016Missouri Plateau (unglaciated Great Plains)
Wibaux County48378816Missouri Plateau (unglaciated Great Plains)
Yellowstone County48397330Missouri Plateau (unglaciated Great Plains)
Carter County47406930Missouri Plateau (unglaciated Great Plains)
Valley County46378016Missouri Plateau (unglaciated Great Plains)
Blaine County45376830Missouri Plateau (unglaciated Great Plains)
Prairie County45426030Missouri Plateau (unglaciated Great Plains)
Teton County45416030Missouri Plateau (unglaciated Great Plains)
Phillips County44386130Missouri Plateau (unglaciated Great Plains)
Roosevelt County44406130Missouri Plateau (unglaciated Great Plains)
Rosebud County44407116Missouri Plateau (unglaciated Great Plains)
Stillwater County44405930Missouri Plateau (unglaciated Great Plains)
Golden Valley County43405830Missouri Plateau (unglaciated Great Plains)
Petroleum County43416416Missouri Plateau (unglaciated Great Plains)
Richland County42375730Missouri Plateau (unglaciated Great Plains)
Sheridan County40405816Missouri Plateau (unglaciated Great Plains)
Cascade County39375716Missouri Plateau (unglaciated Great Plains)
Deer Lodge County35293446Rocky Mountains
Sanders County35323146Rocky Mountains
Flathead County34303146Rocky Mountains
Beaverhead County33303830Rocky Mountains
Glacier County32303530Rocky Mountains
Granite County30301746Rocky Mountains
Lake County30314016Rocky Mountains
Meagher County30302046Rocky Mountains
Powell County30301946Rocky Mountains
Broadwater County29291646Rocky Mountains
Madison County29311446Rocky Mountains
Gallatin County28293416Rocky Mountains
Lewis and Clark County27302130Rocky Mountains
Lincoln County27302030Rocky Mountains
Jefferson County26282130Rocky Mountains
Silver Bow County26301930Rocky Mountains
Mineral County25291730Rocky Mountains
Missoula County25292516Rocky Mountains
Ravalli County23282216Rocky 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