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South Mountain, Texas
Inside South Mountain's city limits, shrink-swell clay limits houses without basements on 17% of mapped land, the 5th-highest of 5 cities in Coryell County. A shallow water table limits basements on 0%.
That clay share is below Coryell County's 26%. FEMA's flood data list 5 flood losses since 2016 in ZIP code 76528 overlapping the city. Of its 154 homes, 39% were built before 1980; the median dates from 1984.
Data as of October 13, 2026 · sources · in Coryell 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 South Mountain
Foundation repair in South Mountain: shrink-swell clay limits slab homes on 17% of South Mountain's mapped land.
About 100 of South Mountain's 154 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 South Mountain city limits
| Expansive clay (limits slab homes) | 17.2% |
| High water table (limits basements) | 0.0% |
| Septic fields very limited | 80.2% |
| Clay swell (LEP, by area) | 4.5% |
| High-swell land (LEP 6%+) | 17.2% |
| Mapped soil | 1,017 acres |
| Soil series | Share here | Series nationally: expansive clay |
|---|---|---|
| Eckrant | 38% | 8% |
| Bolar | 18% | n/a |
| Oglesby | 17% | n/a |
| Real | 8% | n/a |
| Denton | 3% | n/a |
| Crawford | 2% | n/a |
What the numbers mean here
Clay swell averages a linear extensibility of 4.5% by land area here, and 17% of the land reaches USDA's high class (6% or more). Clay like that swells when wet and shrinks when dry, under 17% of the mapped land.
Clay shrinks as it dries: 100% of Coryell County is in drought on the latest map, and 17% of South Mountain's mapped land has shrink-swell clay.
USDA rates 80% of the land very limited for septic absorption fields.
Drought in Coryell County
100% of Coryell 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 South Mountain. ZIP areas reach past city limits.
| ZIP | Share of city land | Flood losses | Paid |
|---|---|---|---|
| 76528 | 100% | 5 | $209,252 |
Homes in South Mountain
| Housing units | 154 |
| Median year built | 1984 |
| Built before 1980 | 39% |
| Built 2000 or later | 22% |
| Owner-occupied | 77% |
| Median value, owner-occupied | $162,500 |
| Single-family detached | 77% |
Nearby cities
| Place | Distance | Expansive clay | High water table |
|---|---|---|---|
| Gatesville | 4 mi | 21% | under 1% |
| Oglesby | 10 mi | 30% | 0% |
| McGregor | 15 mi | 66% | 0% |
| Crawford | 15 mi | 35% | 0% |
| Valley Mills | 19 mi | 23% | 0% |
| Moody | 21 mi | 81% | 0% |
| Morgan's Point Resort | 24 mi | 5% | 0% |
| Clifton | 24 mi | 33% | 0% |
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