San Mateo County, CA Shrink-Swell Risk
San Mateo County's SSURGO shrink-swell reading
Moderate
In San Mateo County, CA, 62.6% of the surveyed soil carries a "Moderate" shrink-swell rating, 3.05% linear extensibility on average. 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.
Before you rely on this for one address
San Mateo County's reading is an average across the whole county, not a promise about any one lot inside it. A local geotechnical report, typically $1,000-$5,000 (around $2,700 typical), is the only way to know what one lot in San Mateo County will actually do.
Budgeting for San Mateo County, CA
San Mateo 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.
How San Mateo County, CA compares
Among the 3,085 rated counties on this site, San Mateo County, CA ranks 1,154 most-constrained nationally, and 24 of 58 within California. The county spans 449 square miles, home to 742,893 people.
For contrast
Orleans Parish, LA carries this site's most-constrained reading. Clay County, WV and Sharkey County, MS 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 California
Every county in California is on this site, including Santa Cruz County, CA and Alpine County, CA. The full underlying dataset is downloadable directly, one row per county.