Drainage Comes Before the Vapor Barrier, Not Instead of It

Crawl Space Drainage Systems: how it works and when it's the right call.

Drainage matting or perforated drain pipe is installed around the interior perimeter of the crawl space, sitting below where the vapor barrier will later be placed. Water entering the crawl space, whether from groundwater pressure or a wall seep, is caught by that perimeter system and channeled to a sump pit. A sump pump installed in the pit turns on automatically once water reaches a set level and ejects it away from the foundation. Once the drainage is in place and tested, the vapor barrier is installed over the floor and up the walls, and the vents are sealed. A dehumidifier is added last to manage whatever humidity remains once the water source has been addressed and the space is sealed. Skipping any one of these three pieces, drainage, sealing, or dehumidification, tends to leave part of the original problem in place. Epp Foundation Repair sequences the work in that order because each step depends on the one before it: sealing a crawl space that still has an active water source traps that water instead of stopping it, and a dehumidifier cannot keep up in a crawl space that is still open to outside air. Drainage first is what lets the rest of the crawl space encapsulation scope hold.