In Western Washington's maritime climate, unsealed crawl spaces are ground zero for indoor air quality and structural moisture problems. Because soil in Thurston County remains saturated throughout winter and spring, exposed dirt continuously evaporates gallons of water vapor into the crawl space atmosphere.
Historically, building codes only required laying loose 6-mil black polyethylene plastic sheeting over the dirt floor. While inexpensive, standard 6-mil poly has fatal vulnerabilities. It has zero puncture resistance; as soon as a plumber, cable technician, or pest control worker crawls across it, rocks puncture the plastic, creating open moisture vents.
Furthermore, 6-mil poly is laid loosely with simple unsealed overlaps and stops short of concrete foundation walls. Moisture vapor simply flows around the edges, rising upward into subfloor insulation and wooden floor joists where it fosters wood-decay fungi and black mold.
True crawl space encapsulation relies on commercial-grade multi-ply reinforced 12-to-20-mil virgin polyethylene liners. These heavy liners incorporate internal polyester cord scrim grids, making them virtually tear-proof and durable enough for heavy storage and crawl traffic.
Our encapsulation protocol involves smoothing crawl space soil, wrapping all interior support piers, overlapping seams by 12 inches and sealing them with waterproof butyl mastic tape, and mechanically fastening the 20-mil liner up concrete stem walls with termination bars. The result is a clean, bright, airtight vapor barrier that permanently transforms your crawl space.