Napa County, CA Shrink-Swell Risk

Napa County, CA's soil, for shrink-swell risk

Moderate

Napa County, CA: USDA's soil survey rates 55.6% of the county "Moderate" for shrink-swell potential (3.19% 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 Napa County's reading doesn't cover

Two lots a mile apart in Napa County can carry different soil, even though they share one countywide reading. The real answer for one lot is still a site-specific geotechnical report, running about $1,000-$5,000 (typically near $2,700).

What it costs to find out, versus to ignore it

With Napa 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, Napa County, CA is the 1,049-most-constrained of 3,085 rated counties for shrink-swell soil. Within California alone it ranks 20 of 58. Napa County covers 752 square miles and counts 132,727 residents.

For contrast

Orleans Parish, LA carries this site's most-constrained reading. Atlantic County, NJ and El Paso County, TX 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 Amador County, CA and Ventura County, CA. The full underlying dataset is downloadable directly, one row per county.