A Homeowner’s Map of Central Texas Soils
The soil under your home depends on which side of the Balcones Escarpment you’re on. Here’s a homeowner’s map of Central Texas soils.
East: Blackland clay
From San Antonio’s South Side up the I-35 corridor through Round Rock, deep expansive clay dominates — maximum shrink-swell.
West: limestone
In the Hill Country — Boerne, Dripping Springs — thin soils over limestone trade swelling for uneven, rocky bearing.
The seam
Cities right on the escarpment, like San Marcos, get both. Either way, steel piers reach the stable layer.
- East of the escarpment: deep expansive clay.
- West: thin soils over limestone.
- Escarpment cities get a mix of both.
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