Score 22 · moderate · #45 of 100 in NC

Crawl space moisture in Union County, NC

Union County scores moderate: no single wet-soil signal dominates its mapped acres. Where a seasonal water table is reported — 28% of acres — it averages 1.8 ft below grade, shallow enough to reach a typical crawl-space footing.

Size venting or encapsulation

1Water table 1.8 ft
2Wet soils 5%
3Moisture score 22
4EPA radon zone 3

Share of mapped soil acres in Union County, NC by NRCS drainage class (dominant condition), bars to scale; wetter classes highlighted. Covers 100% of mapped acres.

Dominant drainage

Well drained

72% of acres

Group D soils

42%

slow infiltration

Flood-prone acres

any flooding frequency

Ponding

acres where water ponds

Reading the Union County soil survey

The score of 22 combines four parts, each from the USDA survey: wet drainage classes contribute 11.1 points of 100 on their own scale, group D soils 48.1, a shallow water table 20.4, and flooding 5.1; the weights are on the methodology page. The dominant hydrologic group is D (35% of acres): very slow infiltration, high runoff (clays, high water table).

Hydrologic soil groups in Union County by share of acres, columns to scale. Group D and dual groups (x/D) shed water slowly and hold it near the surface.

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 on the soils that report a water table — about 28% of Union County's acres. Venting cannot fix that; it needs drainage — a perimeter drain to daylight or a sump — before any liner goes down.

Union County against the rest of North Carolina

Union County ranks 45 of 100 North Carolina counties, 5 points above the state median of 17. That places it in the middle range, nationally and for the state. Statewide, 30% of mapped soil is in the wet drainage classes; here it is 5%, below the state figure — the score here comes from flooding and ponding rather than drainage class alone. After well drained, the next most common class is moderately well drained at 23%.

Flooding. 5.1% of acres with a flooding class are rated frequent. Flood-prone soils are a minority here, concentrated along streams; the score mostly reflects what happens between floods.

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 Union County by score

Hoke County 22 Anson County 23 Granville County 21 Person County 21

All 100 North Carolina counties

Sources: USDA NRCS SSURGO via Soil Data Access (muaggatt: drclassdcd, hydgrpdcd, flodfreqdcd, pondfreqprs, wtdepannmin), acreage-weighted (survey area NC179; drainage covers 100% of 409,139 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.