Crawl Space Moisture Control.

A crawlspace is susceptible to moisture and deterioration problems because of contact with exposed ground soils. The best approaches for preventing these problems will depend on your climate and the styles of your homes construction. However, the following general guidelines for creating a water – managed foundation system apply to most crawl space designs:

1. Keep all untreated wood materials away from the earth.
2. Provide rain drainage, such as gutters, to conduct rainwater way from the house.
3. Slope the soils away from the house for at least 5 feet at a minimum 5% grade (3 inches in 5 feet). Establish drainage swales to direct rainwater around the house.
4. Add a sill gasket to provide air sealing.
5. Install a protective membrane, such as EPDM-type membrane, to serve as a capillary break that reduces wicking of water from the masonry wall. This membrane, in addition to metal flashing, can serve as a termite wall.
6. Damp-proof the below grade portion of the foundation wall to prevent the wall from absorbing ground moisture by capillary action.
7. Install drainage plane material or gravel against the foundation wall to relieve hydrostatic pressure and channel water to the foundation drain.
8. Provide a foundation drainage system at the bottom of the footing, not on top, when the foundation floor (interior grade) is below the exterior grade. Surround a perforated 4-inch drain pipe with gravel, and cover them with filter fabric.
9. Install 6-mil polyethylene vapor diffusion barrier across the crawl space floor to prevent soil moisture from migrating into the crawl space. Overlap and tape all seams by 12 inches. Seal the polyethylene 6 inches up the crawl space walls. As an option, pour two inches of concrete over this to protect the polyethylene from damage.