Expert: Daniel Humphrey - 12/29/2008

Question
I'm building a small pier and beam cottage and wonder what minimum height you'd recommend for the crawl space. The site is level and the soil is a clayey gumbo. It's located about a hundred miles north of Dallas, TX. Thanks in advance for any advice.

Patrick

Answer
Dear Patrick,

I prefer to build crawl spaces between 24" and 32" to give me some comfort working under there and good air flow. In soils such as yours, I smooth and rake all debris from the dirt, put down 6 mil polyethylene vapor barrier plastic to keep the moisture down, and then cover the plastic with four to six inches of clean sand to crawl in.

The minimum beneath the joists required by code in a residence is 18" and beneath the beams, at least 12". But this is pretty tight. In no case should any untreated wood be closer than six inches to the dirt.

If you enclose the crawl space, put in a good size door to bring materials in and out--bigger than 20" x 24". To provide for ventilation and air circulation, the crawl space must have screened vents in a ratio of one square foot for each 150 square feet of floor above.

Good luck on your project.

Daniel