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Alamo Heights, Texas
Inside Alamo Heights' city limits, shrink-swell clay limits houses without basements on 43% of mapped land, higher than 51% of Texas cities. A shallow water table limits basements on 0%.
That clay share is below Bexar County's 51%. FEMA's flood data list 12 flood losses since 2016 in ZIP code 78209 overlapping the city. Of its 3,701 homes, 74% were built before 1980; the median dates from 1950.
Data as of October 13, 2026 · sources · in Bexar 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 Alamo Heights
Foundation repair in Alamo Heights: shrink-swell clay limits slab homes on 43% of Alamo Heights' mapped land, more than in 51% of Texas cities.
About 2,500 of Alamo Heights' 3,701 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 Alamo Heights city limits
| Expansive clay (limits slab homes) | 42.9% |
| High water table (limits basements) | 0.0% |
| Septic fields very limited | 89.9% |
| Clay swell (LEP, by area) | 5.7% |
| High-swell land (LEP 6%+) | 35.1% |
| Mapped soil | 1,181 acres |
| Soil series | Share here | Series nationally: expansive clay |
|---|---|---|
| Eckrant | 56% | 8% |
| Austin | 8% | 93% |
| Tinn | 4% | n/a |
| Brackett | 4% | 0% |
| Eddy | 4% | 0% |
| Houston Black | 3% | 91% |
What the numbers mean here
Clay swell averages a linear extensibility of 5.7% by land area here, and 35% of the land reaches USDA's high class (6% or more). Clay like that swells when wet and shrinks when dry, under 43% of the mapped land.
Clay shrinks as it dries: 79.6% of Bexar County is in drought on the latest map, and 43% of Alamo Heights' mapped land has shrink-swell clay.
USDA rates 90% of the land very limited for septic absorption fields.
Drought in Bexar County
79.6% of Bexar 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 Alamo Heights. ZIP areas reach past city limits.
| ZIP | Share of city land | Flood losses | Paid |
|---|---|---|---|
| 78209 | over 99% | 12 | $35,941 |
Homes in Alamo Heights
| Housing units | 3,701 |
| Median year built | 1950 |
| Built before 1980 | 74% |
| Built 2000 or later | 12% |
| Owner-occupied | 74% |
| Median value, owner-occupied | $779,400 |
| Single-family detached | 67% |
Nearby cities
| Place | Distance | Expansive clay | High water table |
|---|---|---|---|
| Olmos Park | 1 mi | 65% | 0% |
| Terrell Hills | 1 mi | 74% | 0% |
| San Antonio | 4 mi | 61% | under 1% |
| Castle Hills | 4 mi | 67% | 0% |
| Balcones Heights | 5 mi | 52% | 0% |
| Kirby | 5 mi | 86% | 0% |
| Windcrest | 6 mi | 81% | 0% |
| Hill Country Village | 7 mi | 71% | 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