Crawl Space Foundation

Crawl Space Foundation

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A crawl space should be at least 18 inches high so that you can crawl beneath the house annually to inspect for such things as termite damage.


You can see why they are called “Crawl Spaces.”


The crawl space walls should have screened openings for ventilation.


The finished crawl space should be waterproofed. See "Waterproofing".

A crawl space has several advantages over basements and slabs:

• It gets the house up off the ground (especially important in damp or termite-prone areas).

• It is a lot less expensive than a basement and comparable in price to a slab.

• Duct work and plumbing can run in the crawl space, meaning that they are easy to service and move over the lifetime of the house.

Most of the time, a crawl space is made of cinder block with a brick facing, as shown in the images above.

A crawl space has several disadvantages too:

• Crawl spaces are a never-ending source of moisture in a home, because of contact with the earth. Moisture ruins houses by providing a hospitable environment for mold, fungi, and insects that destroy wood framing.

• Most builders, in an effort to save money, don’t allow any more than the minimum, code required, 18 inch high space. If you’ve ever had to work inside a crawl space 18 inches (minus the room taken up by pipes and ducts), you’ve had a few unkind “words” for the builder.

• Be sure that in the final grading stage of construction, the earth slopes away from the house for at least 6 feet or more. This is important with any kind of foundation.

• The use of drainage swales to direct rainwater around the house and away from the foundation should always be implemented where feasible.

• Don’t trust gutters to protect your foundation from “run off” water.

• Install a 6-mil polyethylene vapor barrier across the crawl space floor. This will help prevent soil moisture from escaping into the crawl space.

• Proper ventilation of the crawl space is important.

• Read my page on crawl space ventilation.

• Insulate crawl space walls only if the crawl space is dry all year, the floor above is not insulated, and all ventilation to the crawl space is blocked.