Johnston County, NC Shrink-Swell Risk

What Johnston County, NC's soil means for a foundation

Low

USDA's SSURGO data puts Johnston County, NC's soil at "Low" shrink-swell potential, an area-weighted linear extensibility of 1.62% across 94.7% of the county's surveyed land. That's as favorable a county-level reading as this dataset produces - standard foundation practice, pending one lot's own geotechnical report.

This is a county figure, not a lot figure

USDA's survey covers the whole of Johnston County, NC at once, not any single address. A site-specific soil report, usually $1,000-$5,000, is what an engineer would actually pull before designing a foundation on a lot in Johnston County.

Report cost vs. repair cost

With Johnston County, NC 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.

How Johnston County, NC compares

Nationally, Johnston County, NC is the 2,357-most-constrained of 3,085 rated counties for shrink-swell soil. Within North Carolina alone it ranks 57 of 100. The county spans 792 square miles, home to 249,794 people.

For contrast

Orleans Parish, LA carries this site's most-constrained reading. Bexar County, TX and Graham County, KS 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 North Carolina

Every county in North Carolina is on this site, including New Hanover County, NC and Tyrrell County, NC. The full underlying dataset is downloadable directly, one row per county.