St. Clair County, MO Shrink-Swell Risk
St. Clair County's SSURGO shrink-swell reading
Low
In St. Clair County, MO, 61.4% of the surveyed soil carries a "Low" shrink-swell rating, 2.63% linear extensibility on average. That's the easiest starting point on this site's scale - a standard foundation is the reasonable default here, though any one lot can still differ.
Before you rely on this for one address
St. Clair County's reading is an average across the whole county, not a promise about any one lot inside it. The real answer for one lot is still a site-specific geotechnical report, running about $1,000-$5,000 (typically near $2,700).
Budgeting for St. Clair County, MO
St. Clair County's soil reading points toward standard foundation practice as the likely outcome, not the exception. 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
Among the 3,085 rated counties on this site, St. Clair County, MO ranks 1,462 most-constrained nationally, and 85 of 114 within Missouri. St. Clair County, MO is 675 square miles with a population of 9,848.
Before you act on this
Orleans Parish, LA carries this site's most-constrained reading. Christian County, KY and Ben Hill County, GA 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
Elsewhere in Missouri
Every county in Missouri is on this site, including Pike County, MO and Daviess County, MO. The full underlying dataset is downloadable directly, one row per county.