To maximize your home's energy efficiency and to protect the foundation,
you should use the following moisture and air leakage control techniques
when installing slab-on-grade floors:
Keep all untreated wood materials away from the earth.
Install well-designed guttering and downspouts that are connected
to a drainage system, which diverts rainwater completely away from
Add a sill gasket membrane between the slab and bottom plate to provide air sealing.
Install a protective membrane (such as rubberized roofing material
or ice-dam protection membranes) to serve as a capillary break that
reduces wicking of water up from the foundation. This membrane can
also serve as a termite shield.
Install a foundation drain directly beside the bottom of the footing.
The foundation drain assembly includes a filter fabric, gravel, and
a perforated plastic drain pipe typically 4 inches in diameter. Locate
the drain beside the footing, not on top, to avoid water flowing against
the seam between the footing and the foundation wall, and to prevent
wicking from a web footing through the stem wall.
Install a capillary break and moisture barrier under the slab floor,
consisting of a layer of 10-mil polyethylene vapor
retarder placed over at least 4 inches of gravel.