New Castle County, DE Shrink-Swell Risk
New Castle County, DE's soil, for shrink-swell risk
Low
New Castle County, DE: USDA's soil survey rates 98.7% of the county "Low" for shrink-swell potential (1.43% linear extensibility). Among the 3,144 counties on this site, that's the clean result: little shrink-swell movement, standard construction the likely outcome.
What New Castle County's reading doesn't cover
Two lots a mile apart in New Castle County can carry different soil, even though they share one countywide reading. The real answer for one lot is still a site-specific geotechnical report, running about $1,000-$5,000 (typically near $2,700).
What it costs to find out, versus to ignore it
With New Castle County, DE rating "Low", a geotechnical report is still worthwhile before a build, just less urgent than in a high-risk county. A geotechnical report runs $1,000-$5,000, typically around $2,700. Foundation repair, if a specific lot turns out to differ from the county average, runs $5,000-$15,000.
Where this sits nationally
Nationally, New Castle County, DE is the 2,580-most-constrained of 3,085 rated counties for shrink-swell soil. Within Delaware alone it ranks 1 of 3. New Castle County, DE is 426 square miles with a population of 588,093.
For contrast
Orleans Parish, LA carries this site's most-constrained reading. Baker County, OR and Morrison County, MN are worth a look for comparison.
How this reading is built, and its real limits · Moisture management: the cheap fix that works on any soil
More of Delaware
Every county in Delaware is on this site, including Kent County, DE and Sussex County, DE. The full underlying dataset is downloadable directly, one row per county.