Texas / La Salle County
Score 21 · moderate · #77 of 209 in TX
Crawl space moisture in La Salle County, TX
50% of La Salle County's soil falls in hydrologic group D or a dual D group: clays and high water tables that shed water slowly. Where a seasonal water table is reported — 3% of acres — it averages 4.5 ft below grade.
- 1Water table 4.5 ft
- 2Wet soils 3%
- 3Moisture score 21
- 4EPA radon zone 3
Reading the La Salle County soil survey
The score of 21 combines four parts, each from the USDA survey: wet drainage classes contribute 13.8 points of 100 on their own scale, group D soils 56.9, a shallow water table 0.9, and flooding 13; the weights are on the methodology page. The dominant hydrologic group is D (50% of acres): very slow infiltration, high runoff (clays, high water table).
At 4.5 ft the seasonal water table is usually below a crawl-space floor, but the 3% of acres that report one are by definition the wettest parts of the county; on those lots, a wet spring can bring water close to the footings.
La Salle County against the rest of Texas
La Salle County ranks 77 of 209 Texas counties, 3 points above the state median of 18. That places it in the middle range, nationally and for the state. Statewide, 6% of mapped soil is in the wet drainage classes; here it is 3%, below the state figure — the score here comes from heavy group D soils rather than drainage class alone. After well drained, the next most common class is moderately well drained at 35%.
Flooding. 5.9% of acres with a flooding class are rated frequent; 11.7% of acres with a flooding class are rated occasional. That is a large flood-prone share; a crawl space in the floodplain needs flood vents under most local floodplain ordinances, which is a separate rule from R408 and can rule out a fully sealed design. Ponding — water standing at the surface with nowhere to go — affects 33.7% of acres.
What it means for a crawl space here
In a moderate county the soil record is mixed rather than uniformly wet, so conditions vary from lot to lot. Where the lot drains, the model-code default — a vented crawl space with 1 sq ft of net vent per 150 sq ft of floor, or 1 per 1500 with a Class I vapor retarder on the ground — is a reasonable starting point; where the sections above point to a shallow water table or flood-prone soil on your lot, plan as for an elevated county. Either way, check the site first: grading that falls away from the foundation, gutters and downspouts that discharge well clear of it, and a ground cover over bare earth. A wet crawl space in a moderate county points to one of those first.
Radon. EPA radon zone 3. The zone is a county-level prediction; EPA says elevated levels occur in every zone and every home should be tested.
Near La Salle County by score
Sources: USDA NRCS SSURGO via Soil Data Access (muaggatt: drclassdcd, hydgrpdcd, flodfreqdcd, pondfreqprs, wtdepannmin), acreage-weighted (survey area TX283; drainage covers 100% of 971,475 mapped acres); EPA Map of Radon Zones, county table (June 2024 JSON); IRC R408.3 Unvented crawl space, as adopted in S.C. Code Regs. 8-1221 (LII). Checked 2026-10-23.