Home Age & Foundation Risk in Williamson County

How old a home is, and what soil it sits on, are the two things you can know about foundation risk before anyone looks at a crack. This lookup combines 236,929 Williamson County home records from the appraisal district with our county soil zones to give your area an indicative read.

Why age × soil is the shortcut

On the expansive clay east of I-35, foundation risk stacks with age for three reasons. Older slabs largely predate post-tension construction, which became standard here in the mid-1990s precisely because of this soil. Older homes have had more shrink-swell cycles worked into them — every drought-and-rain swing flexes the slab a little. And older lots carry mature trees and aging under-slab plumbing, the two most common hidden aggravators. On the limestone west side, age matters far less, because the ground barely moves. That’s the logic this tool applies — nothing more sophisticated, and it doesn’t need to be. Check which soil your area sits on, and what the current season is doing with the Foundation Stress Index.

How the areas compare

The county picture

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The standout: Taylor and Coupland, where nearly half the housing stock predates 1980 and sits on the deepest Blackland clay in the county — the highest age-plus-soil combination anywhere in WilCo. At the other end, Liberty Hill is mostly new construction on limestone. In between, Round Rock and Georgetown carry the county’s biggest stock of 1980s–90s slabs on transition-zone soil — homes now 25–45 years old, many built before post-tension slabs were standard. If that’s you, the warning signs guide and crack checker are the place to start.

Methodology & source

Home counts come from the Williamson Central Appraisal District public data downloads (data.wcad.org): the Property Characteristics dataset supplies each home’s actual year built, and the Parcels dataset supplies residential use coding. Records are grouped by WCAD appraisal market area, which approximates but does not exactly match city limits or ZIP boundaries; ZIP lookups map to the nearest market area. Of 242,846 records, 236,929 with a usable year built are counted; 5,917 without one are excluded. Data as of July 2026 (characteristics 2026-07-13, parcels 2026-07-27). Soil zones are the same generalized USDA-based zones as our county soil map. WCAD provides its data “As Is” without warranty; so do we. No owner names or personal information were pulled, stored, or published — aggregate counts only. The risk read is an indicative signal, not engineering advice or a prediction about any specific home. WCAD does not publish foundation type, so construction era is used as a disclosed proxy (post-tension slabs became standard locally in the mid-1990s).