Rockwall County, Texas
Shrink-swell clay limits houses without basements on 72% of Rockwall County's mapped land, a higher share than 97% of US counties. A shallow water table limits basements on 2%.
100% of the county is in drought on the October 13, 2026 Drought Monitor map. FEMA's flood data list 26 flood losses here since 2016. 7% of homes were built before 1980, against 50% nationally; the median home dates from 2006.
Data as of October 13, 2026 · sources
expansive clay: shrink-swell limits slab homes
high water table: limits basements
in drought, October 13, 2026
of homes built before 1980
Soil under Rockwall County
| Expansive clay (limits slab homes) | 71.9% |
| High water table (limits basements) | 1.6% |
| Septic fields very limited | 67.3% |
| Clay swell (LEP, by area) | 11.1% |
| High-swell land (LEP 6%+) | 71.9% |
| Mapped soil | 95,047 acres |
| Soil series | Share here | Series nationally: expansive clay |
|---|---|---|
| Houston Black | 35% | 91% |
| Heiden | 15% | 80% |
| Ferris | 8% | n/a |
| Burleson | 7% | 84% |
| Wilson | 6% | 88% |
| Altoga | 4% | n/a |
How we count · survey areas TX612 (2025-09-05)
What the numbers mean here
Clay swell averages a linear extensibility of 11.1% by land area here, and 72% of the land reaches USDA's high class (6% or more). Clay like that swells when wet and shrinks when dry, under 72% of the mapped land.
Clay shrinks as it dries: 100% of the county is in drought on the latest map, and 72% of Rockwall County's mapped land has shrink-swell clay.
Rain over the 12 months to August 2026: 31.45 in, 9.05 in below the 1991-2020 average year of 40.50 in.
USDA rates 67% of the land very limited for septic absorption fields.
Drought
100% of the county is in drought (D1 or worse) on the October 13, 2026 map. Part of the county was in drought in 24 of the last 52 weeks; the most was 100% of its area, in 8 weeks, most recently on the October 13, 2026 map.
| Category, October 13, 2026 | Share of county |
|---|---|
| D0 abnormally dry or worse | 100% |
| D1 moderate drought or worse | 100% |
| D2 severe or worse | 0% |
| D3 extreme or worse | 0% |
| D4 exceptional | 0% |
Flood losses since 2016
26 flood losses since 2016, $1.2 million paid. The worst year was 2018, with 10.
| Year | Flood losses |
|---|---|
| 2016 | 3 |
| 2017 | 2 |
| 2018 | 10 |
| 2019 | 0 |
| 2020 | 0 |
| 2021 | 0 |
| 2022 | 1 |
| 2023 | 2 |
| 2024 | 2 |
| 2025 | 4 |
| 2026 to date | 2 |
Rain
| Average year, 1991-2020 | 40.50 in |
| 12 months to August 2026 | 31.45 in (-9.05) |
| 2025 | 44.23 in (+3.73) |
| Wettest year since 1895 | 2015: 66.27 in |
| Driest year since 1895 | 2005: 20.64 in |
| Days with 1 inch or more, normal at LAVON DAM (10 mi away) | 11.9 |
Homes
| Housing units | 43,580 |
| Median year built | 2006 |
| Built before 1980 | 7% |
| Built 2000 or later | 67% |
| Owner-occupied | 83% |
| Median value, owner-occupied | $415,500 |
| Single-family detached | 85% |
What repairs cost
Published ranges from cost guides, not quotes. More sources, and where they disagree.
Cities in Rockwall County
| City | Expansive clay | High water table | Homes |
|---|---|---|---|
| Fate | 81% | under 1% | 7,109 |
| Heath | 82% | 3% | 3,619 |
| McLendon-Chisholm | 81% | 1% | 1,503 |
| Mobile City | 82% | 0% | 118 |
| Rockwall | 83% | under 1% | 19,328 |
| Royse City | 87% | 4% | 7,146 |
Nearby counties
| Place | Distance | Expansive clay | High water table |
|---|---|---|---|
| Kaufman County, TX | 21 mi | 73% | 16% |
| Collin County, TX | 23 mi | 72% | 1% |
| Dallas County, TX | 23 mi | 51% | 6% |
| Hunt County, TX | 24 mi | 78% | 17% |
| Rains County, TX | 36 mi | 60% | 34% |
| Van Zandt County, TX | 41 mi | 46% | 35% |
| Ellis County, TX | 44 mi | 72% | 4% |
| Denton County, TX | 46 mi | 50% | 1% |
Sources: USDA SSURGO (September 5, 2025) · US Drought Monitor (October 13, 2026) · FEMA NFIP v3 (September 9, 2026) · NOAA (August 2026) · Census ACS 2020-2024. Methods · Data status