Why Do Foundations Crack in North Texas?
Soil and drought figures for seven counties, pulled from public data and recomputed on every build.
Foundations in North Texas crack mostly because clay soil changes volume with its water content. HGS Engineering, PLLC (Texas Firm #21268) pulled the USDA soil survey for seven counties and found that 56.1% of the rated soil, by acre, is in the high or very high shrink-swell classes. Collin County is highest at 74.5% and Parker County lowest at 9.3%.
Reviewed by Heath Salmon, PE, October 16, 2026. Soil data downloaded 2026-10-16, drought data downloaded 2026-10-16.
Which Counties Have the Most Expansive Soil?
The chart and table rank the seven counties by the share of rated soil acres in the high or very high shrink-swell classes. The USDA rates a soil by linear extensibility, the percent a clod of it lengthens between oven-dry and wet. At nine percent or more the rating is very high. Collin County leads with 74.5%, Ellis County follows with 71.7%, and Parker County is the outlier at 9.3%. Leave Parker out and the other six together come to 64.4%.
| County | High or very high | Very high | Not rated | Weeks in D2 or worse | Weeks, half in D3 |
|---|---|---|---|---|---|
| Collin | 74.5% | 65.5% | 18% | 51 of 262 | 14 |
| Ellis | 71.7% | 54.1% | 14.4% | 59 of 262 | 19 |
| Dallas | 63.9% | 44.4% | 31.4% | 61 of 262 | 18 |
| Denton | 60.6% | 17.5% | 16.1% | 67 of 262 | 13 |
| Johnson | 59.6% | 21.9% | 14.2% | 70 of 262 | 27 |
| Tarrant | 54.2% | 12.7% | 27.5% | 74 of 262 | 22 |
| Parker | 9.3% | 0.4% | 16.2% | 80 of 262 | 21 |
What Does the Drought Record Add?
Soil that can swell has to be dried before it can be rewetted, and the Drought Monitor says how often that happened. Between 2021-10-12 and 2026-10-13, Parker County had some land in severe drought (D2) or worse in 80 of 262 weeks, the most of the seven, and Collin County had 51, the fewest. The county with the most active clay, Collin, has the fewest drought weeks of the seven, while Parker, with the least clay, has the most.
The latest weekly map, dated 2026-10-13, puts 20.87% of Denton County in extreme drought (D3) or worse, the largest share of the seven. Counties are moving through this at different speeds, and each county page gives its year-by-year count.
What Can These Numbers Not Tell You?
A soil survey maps units of many acres, so it describes a county and says nothing certain about one lot. Between 14.2% and 31.4% of each county is unrated, mostly urban land and water, and fill brought in for a subdivision does not appear at all. The drought statistics describe the whole county for a week, so a county that is partly in D2 counts for that week.
Neither data set tells you whether a particular house has moved. That is found by measuring floor levels, reading crack patterns, checking the grade and the gutters, and noting any earlier repair. An engineer does that on site, and the report is sealed. HGS Engineering, PLLC does not perform foundation repairs, so its report has no repair to sell. The fee is quoted on request by email, the only way the firm takes requests.
Where Do the County Pages Go Next?
- Collin County: 74.5% high or very high, 51 weeks in D2 or worse, 1 city page on this site.
- Ellis County: 71.7% high or very high, 59 weeks in D2 or worse, 1 city page on this site.
- Dallas County: 63.9% high or very high, 61 weeks in D2 or worse, 2 city pages on this site.
- Denton County: 60.6% high or very high, 67 weeks in D2 or worse, 1 city page on this site.
- Johnson County: 59.6% high or very high, 70 weeks in D2 or worse, 1 city page on this site.
- Tarrant County: 54.2% high or very high, 74 weeks in D2 or worse, 4 city pages on this site.
- Parker County: 9.3% high or very high, 80 weeks in D2 or worse, 1 city page on this site.
- Texas manufactured homes: the Census count by county and what the state publishes, for HUD foundation certifications.
- Foundation inspection by a licensed engineer
How Were These Numbers Made?
Method: the script scripts/soil-sda.py asks the USDA Soil Data Access service for every soil component in each county survey and keeps the linear extensibility readings for the top 100 centimeters. It averages them by depth for each component, assigns the NRCS class, and weights by map-unit acres times the component's share of the unit. The script scripts/drought-usdm.py pulls the weekly county statistics from the Drought Monitor. Both raw pulls sit under data/public in the site repository, and a gate re-runs the scripts and fails if a printed number differs. Together the seven counties have 3,205,028 rated acres.
Frequently Asked Questions
Why do foundations crack in North Texas?
Because much of the ground is clay. It swells when it soaks and shrinks as it dries, and the slab on top follows unevenly. Across the seven counties studied, 56.1% of rated soil acres are high or very high shrink-swell.
Which North Texas county has the most expansive soil?
Collin County, at 74.5% of rated acres in the high or very high classes. Ellis County is next at 71.7% and Parker County is last at 9.3%.
Does a low shrink-swell county mean no foundation problems?
No. Parker County has the lowest soil share and also had 80 weeks with some land in severe drought since 2021. Fill, drainage, plumbing leaks and tree roots move slabs on any soil, and a soil survey describes a county, not a lot.
Where do these numbers come from?
Two public sources: the USDA NRCS Soil Data Access service (SSURGO), downloaded 2026-10-16, and the U.S. Drought Monitor county statistics, downloaded 2026-10-16. The raw files sit in the site repository, and every printed number is recomputed from them.
Can I use this to decide whether my house needs repair?
No. These numbers describe a county. To learn whether one house has moved, someone has to measure it, and that is what a sealed engineering inspection does. The firm sells no repair work.
Sources
- USDA Natural Resources Conservation Service, Soil Data Access web service (SSURGO tabular data)Linear extensibility (lep_r), map unit acres and component percent for the seven counties, queried on 2026-10-16.
- National Drought Mitigation Center, University of Nebraska-Lincoln, U.S. Drought Monitor data services, county statisticsWeekly percent of each county in D2 (severe) or worse and D3 (extreme) or worse, October 2021 to October 2026.
- Texas Board of Professional Engineers and Land Surveyors, Engineering Firm RegistrationThe firm registration number and the licensed engineer seal.
- Texas Section, American Society of Civil Engineers, Guidelines for the Evaluation and Repair of Residential Foundations, Version 3Foundation evaluation practice, drainage away from the foundation and North Texas soil movement.
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