A basement crawl space is an area below the home that's too small to be considered a true basement. Generally, a basement crawl space is just a few feet deep, and is not tall enough for the homeowner to stand in comfortably. Instead, he can crawl or kneel within the space while accessing mechanical or electrical equipment. The walls of the crawl space also serve as foundation walls for the home, while the crawl space area itself provides some separation between the home and the ground below. Basements and crawl spaces serve as popular alternatives to slab-on-grad construction, where the ground floor of the home sits directly on the ground.
In many homes, the piping and wiring for the home's mechanical and electrical systems run below the first floor. In the absence of a full basement, a basement crawl space makes it easy to reach these items. The homeowner or repair personnel can enter the crawl space and replace or restore these lines, or perform any required upgrades. A basement crawl space also allows the homeowner to access and repair the home's structural foundation, as well as insulation or framing under the first floor.
The average basement crawl space has a dirt floor and concrete walls. The wooden rafters that support the first floor make up the ceiling of the crawl space. Some may have a radon shield or some form of moisture barrier lining the ground, while others do not. A small percentage of homeowners may finish the crawl space with drywall or other materials to create a cleaner environment for storage. Others simply wrap items or store them in protective packaging before placing them in the crawl space.
Users enter the basement crawl space through a trapdoor located somewhere in the floor of the home. Some may also include an outdoor access panel. These doors should be secured to prevent thieves from using them to enter the home.
Moisture, mildew, and pests are frequent problems in the average crawl space. Because of the danger that mold and mildew pose to human health, moisture within the crawl space must be carefully controlled. Air vents can help reduce moisture problems, as can moisture and vapor barriers. Uncontrolled moisture and humidity not only create health risks, but also lead to rot and other forms of home damage.
Basement crawl spaces provide an excellent opportunity to improve the energy efficiency of a house. By insulating the walls and ceiling of the space, homeowners reduce energy consumption and cut heating costs. Well-insulated crawl spaces also reduce drafts and make the home more comfortable.