San Joaquin County, CA Shrink-Swell Risk
San Joaquin County, CA's soil, for shrink-swell risk
Moderate
San Joaquin County, CA: USDA's soil survey rates 45.9% of the county "Moderate" for shrink-swell potential (4.02% linear extensibility). That's a middle reading: not the sharp swings that crack a foundation outright, but enough that grading and drainage are worth getting right.
What San Joaquin County's reading doesn't cover
Two lots a mile apart in San Joaquin 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 San Joaquin County.
What it costs to find out, versus to ignore it
With San Joaquin County, CA 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, San Joaquin County, CA is the 550-most-constrained of 3,085 rated counties for shrink-swell soil. Within California alone it ranks 8 of 58. San Joaquin County, CA is 1,392 square miles with a population of 816,108.
See how another county compares
Orleans Parish, LA carries this site's most-constrained reading. Fallon County, MT and Webster 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
More of California
Every county in California is on this site, including Napa County, CA and Alpine County, CA. The full underlying dataset is downloadable directly, one row per county.