Expansive Soil in Illinois: County Ratings
21 of the 102 rated counties in Illinois have a dominant shrink-swell rating of High or Very High. Each rating below is the NRCS shrink-swell class covering the largest share of the county's mapped soil acres, computed from USDA SSURGO data. Open a county for the full class breakdown and what it means for a slab foundation.
| County | Dominant class | High + Very High share | Survey coverage |
|---|---|---|---|
| Adams County | Moderate | 37% | 98% |
| Alexander County | Low | 24% | 92% |
| Bond County | High | 62% | 98% |
| Boone County | Moderate | 0% | 99% |
| Brown County | Moderate | 27% | 98% |
| Bureau County | Moderate | 1% | 99% |
| Calhoun County | Low | 3% | 88% |
| Carroll County | Moderate | 6% | 95% |
| Cass County | Moderate | 11% | 97% |
| Champaign County | Moderate | 23% | 99% |
| Christian County | High | 56% | 99% |
| Clark County | Moderate | 36% | 99% |
| Clay County | High | 64% | 100% |
| Clinton County | High | 60% | 94% |
| Coles County | Moderate | 9% | 99% |
| Cook County | Moderate | 32% | 80% * |
| Crawford County | High | 43% | 99% |
| Cumberland County | High | 56% | 99% |
| De Witt County | Moderate | 18% | 98% |
| DeKalb County | Moderate | 15% | 99% |
| Douglas County | Moderate | 38% | 99% |
| DuPage County | Moderate | 25% | 98% |
| Edgar County | Moderate | 15% | 100% |
| Edwards County | Low | 30% | 99% |
| Effingham County | High | 59% | 100% |
| Fayette County | High | 52% | 98% |
| Ford County | High | 54% | 100% |
| Franklin County | High | 43% | 94% |
| Fulton County | Moderate | 18% | 96% |
| Gallatin County | Low | 17% | 98% |
| Greene County | Moderate | 18% | 99% |
| Grundy County | Moderate | 19% | 97% |
| Hamilton County | High | 40% | 100% |
| Hancock County | Moderate | 42% | 97% |
| Hardin County | Moderate | 1% | 96% |
| Henderson County | Moderate | 5% | 94% |
| Henry County | Moderate | 10% | 99% |
| Iroquois County | High | 44% | 100% |
| Jackson County | Moderate | 28% | 96% |
| Jasper County | High | 65% | 99% |
| Jefferson County | High | 37% | 97% |
| Jersey County | Moderate | 11% | 98% |
| Jo Daviess County | Moderate | 17% | 97% |
| Johnson County | Moderate | 2% | 99% |
| Kane County | Moderate | 5% | 96% |
| Kankakee County | Moderate | 9% | 99% |
| Kendall County | Moderate | 13% | 98% |
| Knox County | Moderate | 22% | 99% |
| La Salle County | Moderate | 25% | 98% |
| Lake County | Moderate | 14% | 87% |
| Lawrence County | Low | 29% | 98% |
| Lee County | Moderate | 2% | 99% |
| Livingston County | Moderate | 47% | 99% |
| Logan County | Moderate | 23% | 99% |
| Macon County | Moderate | 30% | 98% |
| Macoupin County | High | 58% | 99% |
| Madison County | Moderate | 33% | 96% |
| Marion County | High | 62% | 99% |
| Marshall County | Moderate | 18% | 97% |
| Mason County | Low | 1% | 95% |
| Massac County | Moderate | 10% | 98% |
| McDonough County | Moderate | 43% | 100% |
| McHenry County | Moderate | 2% | 92% |
| McLean County | Moderate | 18% | 99% |
| Menard County | Moderate | 15% | 99% |
| Mercer County | Moderate | 7% | 98% |
| Monroe County | Moderate | 21% | 97% |
| Montgomery County | High | 65% | 98% |
| Morgan County | Moderate | 28% | 99% |
| Moultrie County | Moderate | 34% | 97% |
| Ogle County | Moderate | 4% | 99% |
| Peoria County | Moderate | 22% | 96% |
| Perry County | Moderate | 33% | 97% |
| Piatt County | Moderate | 32% | 100% |
| Pike County | Moderate | 7% | 97% |
| Pope County | Moderate | 2% | 98% |
| Pulaski County | Moderate | 13% | 98% |
| Putnam County | Moderate | 3% | 91% |
| Randolph County | Moderate | 21% | 97% |
| Richland County | High | 61% | 99% |
| Rock Island County | Moderate | 2% | 93% |
| Saline County | Low | 17% | 98% |
| Sangamon County | Moderate | 39% | 98% |
| Schuyler County | Moderate | 30% | 98% |
| Scott County | Moderate | 21% | 99% |
| Shelby County | High | 48% | 98% |
| St. Clair County | Moderate | 27% | 95% |
| Stark County | Moderate | 19% | 100% |
| Stephenson County | Moderate | 8% | 99% |
| Tazewell County | Moderate | 16% | 96% |
| Union County | Moderate | 9% | 97% |
| Vermilion County | Moderate | 32% | 99% |
| Wabash County | Moderate | 12% | 97% |
| Warren County | Moderate | 6% | 100% |
| Washington County | High | 42% | 99% |
| Wayne County | High | 48% | 99% |
| White County | Low | 12% | 98% |
| Whiteside County | Low | 2% | 97% |
| Will County | Moderate | 19% | 97% |
| Williamson County | Low | 19% | 94% |
| Winnebago County | Moderate | 7% | 96% |
| Woodford County | Moderate | 34% | 96% |
* Less than 80% of this county's map acres have completed soil survey data; treat its rating as provisional.
How these ratings are computed
Ratings come from USDA NRCS SSURGO soil survey data: for each soil component we take the maximum linear extensibility percent (lep_r) in the top 100 cm, apply the NRCS Handbook Part 618 class limits (Low under 3 percent, Moderate 3 to 6, High 6 to 9, Very High 9 and above), assign map units by plurality of component percent, and roll acres up to the county. Full details on the methodology section of the lookup page. A county rating is not a parcel-level geotechnical assessment.