North Carolina / Duplin County
Score 44 · elevated · #28 of 100 in NC
Crawl space moisture in Duplin County, NC
Duplin County scores elevated because several moderate signals stack up rather than one dominant one. Where a seasonal water table is reported — 93% of acres — it averages 1.9 ft below grade, shallow enough to reach a typical crawl-space footing.
- 1Water table 1.9 ft
- 2Wet soils 40%
- 3Moisture score 44
- 4EPA radon zone 3
Reading the Duplin County soil survey
The score of 44 combines four parts, each from the USDA survey: wet drainage classes contribute 48.1 points of 100 on their own scale, group D soils 26.8, a shallow water table 66, and flooding 13.9; the weights are on the methodology page. The dominant hydrologic group is B (27% 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 Duplin County. Venting cannot fix that; it needs drainage — a perimeter drain to daylight or a sump — before any liner goes down.
Duplin County against the rest of North Carolina
Duplin County ranks 28 of 100 North Carolina counties, 27 points above the state median of 17. Wetter counties exist in North Carolina, but the soil here still sits well above the national middle. Statewide, 30% of mapped soil is in the wet drainage classes; here it is 40%. After well drained, the next most common class is poorly drained at 33%.
Flooding. 10.4% of acres with a flooding class are rated frequent; 3.8% of acres with a flooding class are rated occasional; 5.9% 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 Duplin County by score
All 100 North Carolina counties
Sources: USDA NRCS SSURGO via Soil Data Access (muaggatt: drclassdcd, hydgrpdcd, flodfreqdcd, pondfreqprs, wtdepannmin), acreage-weighted (survey area NC061; drainage covers 99% of 524,429 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.