St. Louis city, MO Shrink-Swell Risk
Shrink-swell potential in St. Louis city, MO
Moderate
Soil across 70.6% of St. Louis city, MO comes back "Moderate" in USDA's shrink-swell data, averaging 3.3% linear extensibility. Conventional foundations are the reasonable expectation here, with routine moisture-control practice rather than special engineering.
What this number does and doesn't tell you
This is a countywide, area-weighted figure across every soil survey map unit in St. Louis city, MO - never a reading for one specific parcel. The real answer for one lot is still a site-specific geotechnical report, running about $1,000-$5,000 (typically near $2,700).
St. Louis city: the real numbers
St. Louis city'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. Louis city, MO ranks 971 most-constrained nationally, and 70 of 114 within Missouri. St. Louis city, MO is 62 square miles with a population of 279,695.
Before you act on this
Orleans Parish, LA carries this site's most-constrained reading. Wirt County, WV and Calhoun County, AL 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 New Madrid County, MO and Nodaway County, MO. The full underlying dataset is downloadable directly, one row per county.