Johnson County, IL Shrink-Swell Risk

What Johnson County, IL's soil means for a foundation

Low

USDA's SSURGO data puts Johnson County, IL's soil at "Low" shrink-swell potential, an area-weighted linear extensibility of 2.43% across 63.3% 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 Johnson County, IL 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 Johnson County.

Report cost vs. repair cost

With Johnson County, IL 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 Johnson County, IL compares

Nationally, Johnson County, IL is the 1,614-most-constrained of 3,085 rated counties for shrink-swell soil. Within Illinois alone it ranks 99 of 101. The county spans 344 square miles, home to 13,320 people.

For contrast

Orleans Parish, LA carries this site's most-constrained reading. Jackson County, IA and Polk County, TN 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 Illinois

Every county in Illinois is on this site, including Mason County, IL and Wabash County, IL. The full underlying dataset is downloadable directly, one row per county.