BasementSoil

Colorado: basement moisture and foundation risk by county

64 counties, ranked by our combined index. Highest combined risk is Dolores County (55), lowest is Grand County (24). The worst soil for foundation cracks specifically is in Adams County.

CountyIndexMoistureCracksWater tableRegion
Dolores County55379730Colorado Plateau
Larimer County523610016Front Range: Pierre Shale and Denver Formation
Adams County513410016Front Range: Pierre Shale and Denver Formation
Arapahoe County513410016Front Range: Pierre Shale and Denver Formation
Boulder County513310016Front Range: Pierre Shale and Denver Formation
Douglas County513310016Front Range: Pierre Shale and Denver Formation
El Paso County513310016Front Range: Pierre Shale and Denver Formation
Fremont County513510016Front Range: Pierre Shale and Denver Formation
Mesa County51378730Colorado Plateau
Pueblo County513410016Front Range: Pierre Shale and Denver Formation
Teller County513510016Front Range: Pierre Shale and Denver Formation
Elbert County50368330Front Range: Pierre Shale and Denver Formation
Jefferson County50368330Front Range: Pierre Shale and Denver Formation
Montrose County50348730Colorado Plateau
Gilpin County49369216Front Range: Pierre Shale and Denver Formation
Delta County48349216Colorado Plateau
Weld County47378416Front Range: Pierre Shale and Denver Formation
Custer County46348616Front Range: Pierre Shale and Denver Formation
Denver County46387916Front Range: Pierre Shale and Denver Formation
Broomfield County45367816Front Range: Pierre Shale and Denver Formation
Hinsdale County42356230Colorado Plateau
Ouray County42357216Colorado Plateau
Rio Blanco County42356130Colorado Plateau
San Juan County42346330Colorado Plateau
Montezuma County41355630Colorado Plateau
San Miguel County40345730Colorado Plateau
Garfield County39346416Colorado Plateau
Kiowa County37315030High Plains
Clear Creek County36293946Rocky Mountains
Gunnison County36313746Rocky Mountains
La Plata County36365016Colorado Plateau
Las Animas County35344916High Plains
Logan County35305716High Plains
Phillips County35314430High Plains
Washington County35304730High Plains
Eagle County34283446Rocky Mountains
Bent County33324816High Plains
Morgan County33324816High Plains
Cheyenne County32303530High Plains
Lake County32313530Rocky Mountains
Mineral County32302546Rocky Mountains
Moffat County32282746Rocky Mountains
Park County32293830Rocky Mountains
Alamosa County31292446Rocky Mountains
Baca County31342630High Plains
Costilla County31314316High Plains
Prowers County31324116High Plains
Sedgwick County31323916High Plains
Summit County30283230Rocky Mountains
Conejos County29312530Rocky Mountains
Yuma County29313416High Plains
Crowley County28332916High Plains
Pitkin County28281646Rocky Mountains
Saguache County28303316Rocky Mountains
Chaffee County27282230Rocky Mountains
Huerfano County27332616High Plains
Kit Carson County27303016High Plains
Otero County27332516High Plains
Lincoln County26322516High Plains
Archuleta County25282616Rocky Mountains
Jackson County25292616Rocky Mountains
Rio Grande County25281830Rocky Mountains
Routt County25282816Rocky Mountains
Grand County24281530Rocky Mountains

Values from USDA NRCS SSURGO where available, otherwise our regional model — each county page states which. Methodology.

The physiographic regions inside Colorado

State lines are political; soil follows geology. These are the distinct ground types inside Colorado and why each behaves the way it does.

Rocky Mountains

Shallow bedrock and coarse material. Basements are shallow or absent, and the problem is spring meltwater rather than a water table.

18 counties: Alamosa County, Archuleta County, Chaffee County, Clear Creek County, Conejos County, Eagle County, Grand County, Gunnison County, Jackson County, Lake County, Mineral County, Moffat County, Park County, Pitkin County, Rio Grande County, Routt County, Saguache County, Summit County

High Plains

The water table is tens of metres down and rainfall is low. Basement damp here is nearly always condensation or a failed supply line rather than groundwater — and that distinction is worth thousands of dollars.

18 counties: Baca County, Bent County, Cheyenne County, Costilla County, Crowley County, Huerfano County, Kiowa County, Kit Carson County, Las Animas County, Lincoln County, Logan County, Morgan County, Otero County, Phillips County, Prowers County, Sedgwick County, Washington County, Yuma County

Front Range: Pierre Shale and Denver Formation

The best-known expansive soil region in the United States. The risk is not a wet basement — rainfall is low and the water table deep. The risk is heave: wetted bentonitic clay lifts slabs and load-bearing walls. That is why local practice uses void forms under grade beams and drilled piers.

16 counties: Adams County, Arapahoe County, Boulder County, Broomfield County, Custer County, Denver County, Douglas County, El Paso County, Elbert County, Fremont County, Gilpin County, Jefferson County, Larimer County, Pueblo County, Teller County, Weld County

Colorado Plateau

Arid, so groundwater is rarely the problem, but Mancos Shale is strongly expansive and some soils are also gypsiferous, which dissolves. Two mechanisms that both move a footing without any water reaching the basement.

12 counties: Delta County, Dolores County, Garfield County, Hinsdale County, La Plata County, Mesa County, Montezuma County, Montrose County, Ouray County, Rio Blanco County, San Juan County, San Miguel County

Page data updated