DIY Network

Foundations and French Drains From "Healthy Household Workshop" episode DHHW-101

Foundation Types

• Pier - good for slopes and coastal areas. The house is elevated from the ground, reducing the entrance of gas and moisture into the house.

• Slab - a good choice for hot climates where the warmer ground will keep the slab close to the indoor temperature. In cold areas, the slab is cooler than the indoor temperature, leading to condensation and mold.

• Basement - the best choice for colder climates.

• Crawl space - along with a basement and slab foundation, is a good choice for milder climates.

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	French drain
	Sump pump

French Drains

French drains provide a good drainage solution to owners of existing homes or those building a new home. A French drain is a small, sloping trench filled with gravel and sand that draws water away from the foundation of the home and eliminates the potential for mildew and mold.

French drains are inexpensive and easy to construct, and many contractors have started adding them under the slab. Including the drain as part of the slab restricts the capillary action of concrete (the absorption of water into the foundation).

In this healthy house, the contractors lay out and stake perforated tubing throughout the seat. The seat is covered in 8" of gravel to keep the concrete from taking in moisture (the gravel draws the moisture away) and holds the tubing in place. As an added element of protection, the gravel also blocks radon gas from entering the home through the foundation.

In an existing basement, a French drain and sump pump can be used in tandem to eliminate moisture problems. A sump pump can be installed by digging an 8-10" trench around the perimeter of the existing basement -- as well as space for the pump. Once the pump is installed, the remaining trenches are filled with gravel, sand and perforated tubing. New concrete is poured to fill the trench. When the water fills the reservoir, the pump eliminates the water.