Expansive Soil in Connecticut: County Ratings
None of the 8 rated counties in Connecticut 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 |
|---|---|---|---|
| Fairfield County | Low | 0% | 91% |
| Hartford County | Low | 0% | 94% |
| Litchfield County | Low | 0% | 95% |
| Middlesex County | Low | 0% | 94% |
| New Haven County | Low | 0% | 93% |
| New London County | Low | 0% | 94% |
| Tolland County | Low | 0% | 96% |
| Windham County | Low | 0% | 95% |
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.