Short answer
We do not encapsulate crawlspaces because trapping plastic against damp soil and stem walls hides hydraulic problems—it does not remove them. In Puget Sound clay and till, encapsulation can increase hydrostatic pressure, conceal rot, and leave you with musty air and structural damage behind a white liner.
Dive deep
Encapsulation marketing promises a “clean, dry” crawlspace by sealing vents and covering the ground and sometimes walls with polyethylene. That is a passive barrier. Water still moves through capillaries in the footing, collects from lateral flow on glacial till, and builds vapor pressure under the liner. You may see lower humidity briefly while moisture migrates into wood framing out of sight.
Trapping moisture against foundation walls accelerates spalling and rebar corrosion where steel is present. Soil gases including radon can concentrate if not actively vented. When the liner tears or condensates under the plastic, mold grows on joists above the sheet—exactly the rot encapsulation claimed to prevent.
Our alternative is active water diversion: perimeter French drains at the footing, dimple board to break capillary contact, sealed sump basins with redundant pumps, and targeted ventilation where soil gas is a concern. We solve the source—groundwater path and pressure—instead of cosmetically wrapping the symptom. If another company sells encapsulation as waterproofing, ask where the water goes before it hits the plastic.
Ventilation without source control can pull more damp soil air through the crawlspace. We prefer measured fan and dehumidifier strategy after drainage lowers the water table—not a dehumidifier fighting an open pit and saturated perimeter.
We would rather lose a crawlspace liner sale than install a system we know traps water against your footing.
When it applies
- Musty crawlspace with standing water or efflorescence on stem walls
- Sales proposals for full encapsulation without drainage design or sump specification
- Prior encapsulation with moisture trapped under liner or mold on joists above
- Homes on till or clay with seasonal seepage at the footing
When it does not
- Conditioned crawlspace as part of new engineered construction with full HVAC design—different building science scope than retrofit liner sales
- Vapor barrier over newly poured, dry, drained slab in new build per plans—not a substitute for drainage on wet legacy crawlspaces
- Attic mold from ventilation failure—encapsulation is irrelevant; see attic thermal bridging remediation
What we do next
We inspect moisture paths, install engineered crawlspace drainage and sump where needed, and vent or dehumidify based on measured conditions—not a one-size liner kit.
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