Where this data comes from, and its real limits

The source

Every county's reading comes from USDA's Soil Data Access, specifically chorizon.lep_r (linear extensibility percent) - the lab measurement of how much a soil sample expands when saturated. No cointerp shrink-swell hazard rule exists in the current SDA ruleset; the closest one, "ENG - Construction Materials; Shrink-Swell," rates soil as a source of fill material, not as a foundation hazard, so this site uses the raw lab measurement directly instead.

How the county number is built

For each major soil component, LEP is depth-weighted across the top 100cm (the standard SSURGO aggregate depth). Components are then weighted by their share of the map unit, and map units are weighted by acreage up to a countywide average. The four bands - Low, Moderate, High, Very High - use the standard NRCS Soil Survey Manual breakpoints (3%, 6%, 9% linear extensibility).

Why it's a county figure, not a parcel figure

SSURGO's map units are drawn at roughly 1:12,000-1:63,360 scale - useful for comparing places, not for one address. ShrinkSwellCheck reports the AREA-WEIGHTED reading across every map unit in a county's survey area(s). A real foundation design or repair decision still needs a site-specific geotechnical report; nothing here substitutes for one.

59 counties with no reading

A small number of counties have no matching SSURGO survey data at all, usually because the dominant land cover (already-developed urban land, water) carries no soil interpretation. Those show up here as honestly unrated rather than guessed at.

The cost figures

Geotechnical report cost ($1,000-$5,000) is sourced from Angi's and HomeGuide's 2026 geotechnical-report cost guides. Foundation repair cost ($5,000-$15,000) is sourced from industry cost data on typical expansive-soil foundation repairs. These are national contractor-pricing ranges, not county-specific quotes.

Where to go next

Real counties this plays out on: Orleans Parish, LA, Coos County, OR, Monroe County, FL.

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