The 20 US counties with the highest basement risk in our coverage
Ranked on a combined index of three USDA soil variables: how long the ground stays saturated, how much it changes volume, and how close the water table comes to basement depth. The interesting part is not the ranking — it is that the counties cluster into four pieces of geology.
| # | County | Index | Moisture | Cracks | Water table | Region |
|---|---|---|---|---|---|---|
| 1 | Clay County, MN | 86 | 77 | 100 | 82 | Red River Valley (bed of glacial Lake Agassiz) |
| 2 | Kittson County, MN | 86 | 77 | 100 | 82 | Red River Valley (bed of glacial Lake Agassiz) |
| 3 | Pennington County, MN | 86 | 78 | 100 | 82 | Red River Valley (bed of glacial Lake Agassiz) |
| 4 | Red Lake County, MN | 86 | 78 | 100 | 82 | Red River Valley (bed of glacial Lake Agassiz) |
| 5 | Wilkin County, MN | 86 | 75 | 94 | 95 | Red River Valley (bed of glacial Lake Agassiz) |
| 6 | Traill County, ND | 86 | 77 | 100 | 82 | Red River Valley (bed of glacial Lake Agassiz) |
| 7 | Sargent County, ND | 83 | 78 | 82 | 95 | Red River Valley (bed of glacial Lake Agassiz) |
| 8 | Grand Forks County, ND | 80 | 75 | 75 | 95 | Red River Valley (bed of glacial Lake Agassiz) |
| 9 | Noble County, IN | 79 | 73 | 76 | 95 | Glaciolacustrine lake plain |
| 10 | East Feliciana Parish, LA | 79 | 64 | 89 | 95 | Mississippi alluvial plain |
| 11 | St. James Parish, LA | 79 | 65 | 88 | 95 | Mississippi alluvial plain |
| 12 | Pembina County, ND | 79 | 74 | 84 | 82 | Red River Valley (bed of glacial Lake Agassiz) |
| 13 | Richland County, ND | 79 | 78 | 69 | 95 | Red River Valley (bed of glacial Lake Agassiz) |
| 14 | Brazoria County, TX | 79 | 62 | 100 | 82 | Texas Gulf Coast prairie |
| 15 | Wharton County, TX | 79 | 63 | 100 | 82 | Texas Gulf Coast prairie |
| 16 | St. Helena Parish, LA | 78 | 65 | 84 | 95 | Mississippi alluvial plain |
| 17 | Oakland County, MI | 78 | 72 | 75 | 95 | Glaciolacustrine lake plain |
| 18 | Polk County, MN | 78 | 76 | 77 | 82 | Red River Valley (bed of glacial Lake Agassiz) |
| 19 | Williams County, OH | 78 | 74 | 72 | 95 | Glaciolacustrine lake plain |
| 20 | Jasper County, TX | 78 | 61 | 100 | 82 | Texas Gulf Coast prairie |
Index = 0.45 × moisture + 0.32 × cracks + 0.23 × water table, from USDA SSURGO fields. Full formula.
The geology doing the work
Red River Valley (bed of glacial Lake Agassiz) 11 of the 20
The combination that destroys foundations: no slope, impermeable clay, and extreme volume change. Foundation repair is a bigger trade here than waterproofing.
Clay County, MN, Kittson County, MN, Pennington County, MN, Red Lake County, MN, Wilkin County, MN, Traill County, ND, Sargent County, ND, Grand Forks County, ND, Pembina County, ND, Richland County, ND, Polk County, MN
Glaciolacustrine lake plain 3 of the 20
About the least favourable ground for a basement anywhere in the United States. Dead flat, clay with almost no permeability, and historically wetland that was drained artificially. Basements exist here because the houses were built before anyone modelled the consequence.
Noble County, IN, Oakland County, MI, Williams County, OH
Mississippi alluvial plain 3 of the 20
Basements are rare here and that is sensible. Where they exist they are under more or less permanent groundwater pressure — not a case for a one-off repair, but for a pump with a backup that never stops mattering.
East Feliciana Parish, LA, St. James Parish, LA, St. Helena Parish, LA
Texas Gulf Coast prairie 3 of the 20
Highly expansive clay and a shallow water table on ground with essentially no slope. Houston is the largest single market for residential foundation repair in the country and this soil is why. Add regional subsidence from groundwater withdrawal and the movement is not always the house's fault.
Brazoria County, TX, Wharton County, TX, Jasper County, TX
The other list: worst for foundation cracks, not water
Rank on shrink-swell alone and a different set of counties appears — several of them dry, with deep water tables. This is the distinction that costs American homeowners the most money, because the symptom looks structural and the ground is not wet, so the search results are wrong from the first click.
| County | Linear extensibility | Moisture score | Region |
|---|---|---|---|
| Autauga County, AL | 16.7% | 51 | Blackland Prairie and Black Belt |
| Bullock County, AL | 16.7% | 51 | Blackland Prairie and Black Belt |
| Chilton County, AL | 16.4% | 49 | Blackland Prairie and Black Belt |
| Choctaw County, AL | 14.4% | 49 | Blackland Prairie and Black Belt |
| Crenshaw County, AL | 15.5% | 54 | Blackland Prairie and Black Belt |
| Elmore County, AL | 17.0% | 51 | Blackland Prairie and Black Belt |
| Greene County, AL | 12.5% | 50 | Blackland Prairie and Black Belt |
| Hale County, AL | 15.8% | 52 | Blackland Prairie and Black Belt |
| Lowndes County, AL | 17.8% | 53 | Blackland Prairie and Black Belt |
| Macon County, AL | 15.4% | 52 | Blackland Prairie and Black Belt |
Why expansive clay cracks foundations without any water getting in
If your county is on the first list
It does not mean your basement is wet, and we will not tell you it does. What it means is that the drainage recommendation you get is more likely to be legitimate rather than an upsell, that a sump pump is normal infrastructure rather than an admission of failure, and that backup power deserves to be in the first contract rather than the second.
If your county is on the second list, the opposite advice applies: be sceptical of anyone selling waterproofing, and spend the first few hundred dollars on an independent structural engineer instead.
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