Tennessee / Lauderdale County
Score 40 · elevated · #9 of 88 in TN
Crawl space moisture in Lauderdale County, TN
Lauderdale County scores elevated because several moderate signals stack up rather than one dominant one. Where a seasonal water table is reported — 63% of acres — it averages 1.8 ft below grade, shallow enough to reach a typical crawl-space footing.
- 1Water table 1.8 ft
- 2Wet soils 38%
- 3Moisture score 40
- 4EPA radon zone 3
Reading the Lauderdale County soil survey
The score of 40 combines four parts, each from the USDA survey: wet drainage classes contribute 36.8 points of 100 on their own scale, group D soils 39.7, a shallow water table 45.3, and flooding 40; the weights are on the methodology page. The dominant hydrologic group is B (34% of acres): moderate infiltration.
A water table under two feet is the single most important number here. A crawl-space floor is usually 18 to 36 inches below the joists and often below outside grade, so in a wet season groundwater can stand at or above the crawl-space floor across much of Lauderdale County. Venting cannot fix that; it needs drainage — a perimeter drain to daylight or a sump — before any liner goes down.
Lauderdale County against the rest of Tennessee
Lauderdale County ranks 9 of 88 Tennessee counties, 28 points above the state median of 12. That puts it in the wettest quarter of the state. Statewide, 9% of mapped soil is in the wet drainage classes; here it is 38%, half again the state figure or more. After well drained, the next most common class is somewhat poorly drained at 25%.
Flooding. 13.4% of acres with a flooding class are rated frequent; 44.3% of acres with a flooding class are rated occasional; 0.2% 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 Lauderdale County by score
Sources: USDA NRCS SSURGO via Soil Data Access (muaggatt: drclassdcd, hydgrpdcd, flodfreqdcd, pondfreqprs, wtdepannmin), acreage-weighted (survey area TN097; drainage covers 92% of 324,172 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.