Foundation soil data for every US county

USDA's soil survey rates two soil problems for houses: clay that shrinks and swells under slabs and footings, and water tables shallow enough to reach basements. Here is where each one sits, next to this week's drought map, flood losses since 2016 and the age of the homes.

3,144 counties · 1,227 Texas cities · 922 Ohio cities · drought map of November 3, 2026

15%

of mapped US land: shrink-swell clay limits houses without basements

29%

of mapped US land: a shallow water table limits basements

50%

of US homes were built before 1980 (ACS 2020-2024)

3,144

counties and county-equivalents, each with its own page

Map of US counties shaded by the share of mapped land where shrink-swell clay limits houses without basements
Expansive clay share, contiguous USunder 10%10-25%25-40%40-60%60%+
Map of US counties shaded by the share of mapped land where a shallow water table limits basements
High water table share, contiguous USunder 10%10-25%25-40%40-60%60%+

Where the clay is

Counties with the largest share of mapped land where shrink-swell clay limits houses without basements.

CountyExpansive clay
Jones County, SD94%
Fillmore County, NE91%
Adair County, IA91%
Audrain County, MO90%
Lyman County, SD89%
Stanley County, SD89%
Haakon County, SD89%
Adams County, IA88%
Madison County, IA88%
Shelby County, MO87%

Clay counties in drought this week

Clay shrinks as it dries. These counties have the most land that is both shrink-swell clay and in drought on the November 3, 2026 Drought Monitor map (clay share times drought share).

CountyClay land in drought
Humphreys County, MS86%
Audrain County, MO86%
Floyd County, TX84%
Sharkey County, MS79%
Hunt County, TX78%
Delta County, TX77%
Sunflower County, MS76%
Navarro County, TX75%
Tensas Parish, LA75%
Kaufman County, TX73%

Every expansive clay county, week by week: the drought watch.

Where the water table is shallow

Counties with the largest share of mapped land where a shallow water table limits basements.

CountyHigh water table
Clinch County, GAover 99%
DeSoto County, FL99%
Linn County, MO99%
Baker County, FL99%
Hardee County, FL99%
Van Wert County, OH99%
Berkeley County, SC99%
Hampton County, SC99%
Charlton County, GA99%
Williamsburg County, SC99%

Texas and Ohio cities

Every incorporated city in both states has its own page, measured inside city limits. Largest shares among cities with 5,000+ homes:

Texas cityExpansive clay
Plainview91%
Bay City88%
Royse City87%
Ennis86%
Converse85%
Manor84%
Forney83%
Rockwall83%
Princeton83%
Taylor81%
Ohio cityHigh water table
Washington Court House96%
Pataskala95%
Avon Lake94%
Wilmington93%
Greenville92%
Willowick91%
Aurora89%
Brunswick89%
Hilliard88%
North Ridgeville87%

Largest Texas cities

Largest Ohio cities

All Texas counties and cities · All Ohio counties and cities

Every state

Calculators

Guides

How this site works

Every number comes from public data: USDA's soil survey (SSURGO), the US Drought Monitor, FEMA's flood records, NOAA rainfall and the Census Bureau's housing survey. Scripts pull and check them, and every page shows its sources and dates. Sources and methods · Data status · How we get paid.