Virginia / Mathews County
Score 56 · elevated · #2 of 95 in VA
Crawl space moisture in Mathews County, VA
78% of Mathews County's mapped soil is somewhat poorly to very poorly drained, which means ground that stays wet near the surface for significant periods. Where a seasonal water table is reported — 52% of acres — it averages 0.8 ft below grade, shallow enough to reach a typical crawl-space footing.
- 1Water table 0.8 ft
- 2Wet soils 78%
- 3Moisture score 56
- 4EPA radon zone 3
Reading the Mathews County soil survey
The score of 56 combines four parts, each from the USDA survey: wet drainage classes contribute 78.1 points of 100 on their own scale, group D soils 50.4, a shallow water table 46.2, and flooding 3.8; the weights are on the methodology page. The dominant hydrologic group is B/D (67% of acres): D when undrained, B when drained.
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 52% of Mathews County's acres. Venting cannot fix that; it needs drainage — a perimeter drain to daylight or a sump — before any liner goes down.
Mathews County against the rest of Virginia
Mathews County ranks 2 of 95 Virginia counties, 44 points above the state median of 12. Only 1 other county in the state score higher. Statewide, 11% of mapped soil is in the wet drainage classes; here it is 78%, half again the state figure or more. After poorly drained, the next most common class is well drained at 10%.
Flooding. 3.8% 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 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 Mathews County by score
Sources: USDA NRCS SSURGO via Soil Data Access (muaggatt: drclassdcd, hydgrpdcd, flodfreqdcd, pondfreqprs, wtdepannmin), acreage-weighted (survey area VA115; drainage covers 59% of 66,200 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.