Expansive Soil in Rhode Island: County Ratings
None of the 5 rated counties in Rhode Island 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 |
|---|---|---|---|
| Bristol County | Low | 4% | 54% * |
| Kent County | Low | 7% | 88% |
| Newport County | Low | 1% | 74% * |
| Providence County | Low | 7% | 91% |
| Washington County | Low | 4% | 84% |
* 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.