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Thrall, Texas
Inside Thrall's city limits, shrink-swell clay limits houses without basements on 84% of mapped land, the 3rd-highest of 14 cities in Williamson County. A shallow water table limits basements on under 1%.
That clay share is above Williamson County's 60%. FEMA's flood data list no flood losses since 2016 in ZIP code 76578 overlapping the city. Of its 289 homes, 42% were built before 1980; the median dates from 1984.
Data as of October 13, 2026 · sources · in Williamson County
expansive clay: shrink-swell limits slab homes
high water table: limits basements
flood losses since 2016 in 1 overlapping ZIP
of homes built before 1980
Foundation repair in Thrall
Foundation repair in Thrall: shrink-swell clay limits slab homes on 84% of Thrall's mapped land, more than in 91% of Texas cities.
About 300 of Thrall's 289 homes are detached houses.
| Who designs the repair | The ASCE Texas Section's repair guidelines say a Texas-licensed engineer should evaluate the foundation and design the repair (2022 guidelines) |
| Prices | Cost guide ranges compared |
Soil under Thrall city limits
| Expansive clay (limits slab homes) | 83.7% |
| High water table (limits basements) | 0.1% |
| Septic fields very limited | 83.7% |
| Clay swell (LEP, by area) | 10.5% |
| High-swell land (LEP 6%+) | 83.7% |
| Mapped soil | 298 acres |
| Soil series | Share here | Series nationally: expansive clay |
|---|---|---|
| Burleson | 35% | 84% |
| Branyon | 25% | 92% |
| Houston Black | 17% | 91% |
| Krum | 6% | n/a |
| Heiden | 6% | 80% |
| Wilson | 3% | 88% |
What the numbers mean here
Clay swell averages a linear extensibility of 10.5% by land area here, and 84% of the land reaches USDA's high class (6% or more). Clay like that swells when wet and shrinks when dry, under 84% of the mapped land.
Clay shrinks as it dries: 100% of Williamson County is in drought on the latest map, and 84% of Thrall's mapped land has shrink-swell clay.
USDA rates 84% of the land very limited for septic absorption fields.
Drought in Williamson County
100% of Williamson County is in drought (D1 or worse) on the October 13, 2026 map. County detail.
Flood losses by ZIP code
FEMA flood records since 2016 in the ZIP codes that overlap Thrall. ZIP areas reach past city limits.
| ZIP | Share of city land | Flood losses | Paid |
|---|---|---|---|
| 76578 | 100% | 0 | $0 |
Homes in Thrall
| Housing units | 289 |
| Median year built | 1984 |
| Built before 1980 | 42% |
| Built 2000 or later | 34% |
| Owner-occupied | 72% |
| Median value, owner-occupied | $175,000 |
| Single-family detached | 89% |
Nearby cities
Sources: USDA SSURGO (August 5, 2026) · US Drought Monitor (October 13, 2026) · FEMA NFIP v3 (September 9, 2026) · Census ACS 2020-2024. Methods · Data status