Williamson County foundation soil map
A general look at what your home likely sits on across WilCo — the expansive Blackland clay on the east side, the Edwards limestone on the west — and why it decides how much your foundation moves. Zoom in to your area.
Edwards limestone / transition (west) — lower movement risk
Green outline = Williamson County service area
Disclaimer: This map shows the general, most common soil trend across Williamson County — not a site-specific survey. The real boundary between clay and limestone is gradual and irregular, and any individual lot can differ from the area around it (cut-and-fill grading, pockets of one soil inside the other, and creek bottoms all change the picture). Your home’s actual soil is confirmed by an elevation survey and a geotechnical or structural engineer, not by this map. Base map © OpenStreetMap contributors.
What the two sides mean for your foundation
East of roughly the I-35 corridor — Hutto, Taylor, Pflugerville, and much of Round Rock and Georgetown — homes sit on deep Blackland Prairie clay that swells when wet and shrinks hard in a drought. That seasonal movement is the main driver of slab cracking here. West toward Cedar Park, Leander, and Liberty Hill, the ground trends to Edwards limestone, which barely moves — so foundation problems there are more often about lot grading, drainage, or engineered fill. There’s a full explainer on why east-county homes crack more, and you can check your soil risk by ZIP.
Get a local crew’s read on your foundation
Whatever the map shows, an on-site look is what tells you what’s really happening. We’ll match you with up to three independent local contractors — free, no obligation.
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