Crawl spaces are the hardest radon problem in York County and the one most often done wrong. There is no slab to suck under — just bare soil or gravel that vents radon straight into the space beneath your floor, where it is drawn up into living areas by the same stack effect that pulls warm air out of the roof. Older farmhouses in Windsor, Hellam and Conewago townships, split-levels from the 1960s through the 1980s in Dover and Red Lion, and additions built on a crawl next to an original basement all have this problem, and a standard sub-slab system alone will not fix it.
The correct approach is sub-membrane depressurization. We clean and level the crawl space floor, lay a heavy-gauge (typically 10–20 mil) polyethylene vapor barrier across the entire soil surface, seal it to the foundation walls and around every pier and pipe with mastic and tape, and run a perforated collection pipe or suction point beneath the membrane connected to an inline fan. The fan holds a slight vacuum under the plastic so radon is captured and exhausted above the roof before it can reach the crawl space air. Where a crawl space adjoins a basement, we tie both into a single fan with balanced suction.
Done properly, this also solves the moisture and musty-air problems that come with a dirt crawl space, because the membrane stops soil vapor as well as radon. Many York homeowners notice the first floor feels drier and smells cleaner within a week. If the crawl space has standing water or grading problems we address drainage first, because a membrane over a wet floor won't seal.
We size the fan for the crawl space area and the soil beneath it — the tight shale soils common north of York and the clay pockets in southern York County need more suction than the county's sandy limestone areas — and we confirm the pressure field under the membrane with a micromanometer before we close up. As with every system we install, a post-mitigation test follows and the below-4.0 pCi/L guarantee applies.
Crawl Space Radon Mitigation Services We Offer
✓Sub-Membrane Depressurization
Sealed vapor barrier with an active fan pulling from beneath it.
✓Combination Basement + Crawl Space Systems
One fan serving a sub-slab suction point and a crawl space membrane.
✓Crawl Space Vapor Barrier Sealing
Membrane installation and sealing for moisture and soil-gas control.
Pricing
Crawl space systems typically run $1,800–$3,500 depending on area, access and whether a basement system is combined.