Polk County, IA Shrink-Swell Risk

Polk County, IA's soil, for shrink-swell risk

Moderate

Polk County, IA: USDA's soil survey rates 54% of the county "Moderate" for shrink-swell potential (3.1% linear extensibility). A real but modest amount of movement - standard foundations usually hold up, but drainage and moisture control around the foundation still matter more than on low-risk soil.

What Polk County's reading doesn't cover

Two lots a mile apart in Polk County can carry different soil, even though they share one countywide reading. 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 Polk County.

What it costs to find out, versus to ignore it

With Polk County, IA rating "Moderate", 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, Polk County, IA is the 1,115-most-constrained of 3,085 rated counties for shrink-swell soil. Within Iowa alone it ranks 81 of 99. Polk County covers 573 square miles and counts 516,185 residents.

For contrast

Orleans Parish, LA carries this site's most-constrained reading. Kiowa County, OK and Baltimore city, MD 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 Iowa

Every county in Iowa is on this site, including Washington County, IA and Mitchell County, IA. The full underlying dataset is downloadable directly, one row per county.