Louisiana / Vernon Parish
Score 43 · elevated · #53 of 64 in LA
Crawl space moisture in Vernon Parish, LA
50% of Vernon Parish'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 — 65% of acres — it averages 2.1 ft below grade.
- 1Water table 2.1 ft
- 2Wet soils 33%
- 3Moisture score 43
- 4EPA radon zone 3
Reading the Vernon Parish soil survey
The score of 43 combines four parts, each from the USDA survey: wet drainage classes contribute 42.7 points of 100 on their own scale, group D soils 49.9, a shallow water table 44.8, and flooding 21; the weights are on the methodology page. The dominant hydrologic group is C (29% of acres): slow infiltration (clay layers).
At 2.1 ft the seasonal water table is usually below a crawl-space floor, but the 65% 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.
Vernon Parish against the rest of Louisiana
Vernon Parish ranks 53 of 64 Louisiana counties, 19 points below the state median of 62. Wetter counties exist in Louisiana, but the soil here still sits well above the national middle. Statewide, 64% of mapped soil is in the wet drainage classes; here it is 33%, below the state figure — the score here comes from heavy group D soils rather than drainage class alone. After moderately well drained, the next most common class is well drained at 22%.
Flooding. 18.9% of acres with a flooding class are rated frequent; 3.3% of acres with a flooding class are rated occasional; 0.4% of acres with a flooding class are rated rare. 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.
What it means for a crawl space here
In an elevated county the soil supplies more moisture than average, but a vented crawl space can work if the ground is covered: the code lets vent area drop from 1 sq ft per 150 to 1 per 1500 with a Class I vapor retarder on the ground, which is an admission of how much moisture comes from below. Grading, gutters and a ground cover usually decide whether a crawl space here stays dry before any decision about sealing it.
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 Vernon Parish by score
Sources: USDA NRCS SSURGO via Soil Data Access (muaggatt: drclassdcd, hydgrpdcd, flodfreqdcd, pondfreqprs, wtdepannmin), acreage-weighted (survey area LA115; drainage covers 99% of 858,300 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.