St. Mary Parish, LA Shrink-Swell Risk

Shrink-swell potential in St. Mary Parish, LA

Very High

Soil across 48.8% of St. Mary Parish, LA comes back "Very High" in USDA's shrink-swell data, averaging 10.7% linear extensibility. This is the reading most likely to explain cracking a homeowner is already seeing. An engineered foundation design, not a conventional footing, is the realistic expectation for new construction.

What this number does and doesn't tell you

This is a countywide, area-weighted figure across every soil survey map unit in St. Mary Parish, LA - never a reading for one specific parcel. A local geotechnical report, typically $1,000-$5,000 (around $2,700 typical), is the only way to know what one lot in St. Mary Parish will actually do.

St. Mary Parish: the real numbers

With St. Mary Parish, LA rating "Very High", the gap between finding out early and finding out late is the whole decision. A geotechnical report runs $1,000-$5,000 (typically $2,700); an actual foundation repair, once cracking sets in, typically runs $5,000-$15,000 (around $10,000 typical) - roughly 4x the report.

St. Mary Parish's rank among Louisiana counties

Among the 3,085 rated counties on this site, St. Mary Parish, LA ranks 20 most-constrained nationally, and 13 of 64 within Louisiana. The county spans 559 square miles, home to 46,799 people.

Before you act on this

Orleans Parish, LA carries this site's most-constrained reading. Howard County, AR and Hampden County, MA are worth a look for comparison.

How this reading is built, and its real limits · The warning signs of expansive-clay damage, explained

Elsewhere in Louisiana

Every county in Louisiana is on this site, including Concordia Parish, LA and Lincoln Parish, LA. The full underlying dataset is downloadable directly, one row per county.