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Southmayd, Texas
Inside Southmayd's city limits, shrink-swell clay limits houses without basements on 82% of mapped land, the 3rd-highest of 16 cities in Grayson County. A shallow water table limits basements on 3%, the 4th-highest of 16 cities in Grayson County.
That clay share is above Grayson County's 60%. FEMA's flood data list 39 flood losses since 2016 in the 3 ZIP codes overlapping the city. Of its 540 homes, 10% were built before 1980; the median dates from 1998.
Data as of October 13, 2026 · sources · in Grayson County
expansive clay: shrink-swell limits slab homes
high water table: limits basements
flood losses since 2016 in 3 overlapping ZIPs
of homes built before 1980
Foundation repair in Southmayd
Foundation repair in Southmayd: shrink-swell clay limits slab homes on 82% of Southmayd's mapped land, more than in 89% of Texas cities.
About 200 of Southmayd's 540 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 Southmayd city limits
| Expansive clay (limits slab homes) | 82.4% |
| High water table (limits basements) | 2.5% |
| Septic fields very limited | 93.9% |
| Clay swell (LEP, by area) | 10.7% |
| High-swell land (LEP 6%+) | 76.4% |
| Mapped soil | 1,810 acres |
What the numbers mean here
Clay swell averages a linear extensibility of 10.7% by land area here, and 76% of the land reaches USDA's high class (6% or more). Clay like that swells when wet and shrinks when dry, under 82% of the mapped land.
Clay shrinks as it dries: 100% of Grayson County is in drought on the latest map, and 82% of Southmayd's mapped land has shrink-swell clay.
USDA rates 94% of the land very limited for septic absorption fields.
Drought in Grayson County
100% of Grayson 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 Southmayd. ZIP areas reach past city limits.
| ZIP | Share of city land | Flood losses | Paid |
|---|---|---|---|
| 75092 | 62% | 39 | $1.5 million |
| 76268 | 22% | 0 | $0 |
| 76273 | 15% | 0 | $0 |
Homes in Southmayd
| Housing units | 540 |
| Median year built | 1998 |
| Built before 1980 | 10% |
| Built 2000 or later | 44% |
| Owner-occupied | 91% |
| Median value, owner-occupied | $164,000 |
| Single-family detached | 31% |
Nearby cities
| Place | Distance | Expansive clay | High water table |
|---|---|---|---|
| Sherman | 5 mi | 61% | 3% |
| Dorchester | 6 mi | 73% | under 1% |
| Knollwood | 7 mi | 76% | 0% |
| Sadler | 9 mi | 70% | 0% |
| Howe | 10 mi | 77% | 2% |
| Pottsboro | 10 mi | 66% | 0% |
| Whitesboro | 11 mi | 56% | 0% |
| Collinsville | 12 mi | 40% | 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