Subterranean termites live in colonies located within ground soil, and a single mature colony is composed of millions of individual termites inhabiting a network of interconnected nesting sites. Most individuals within a colony are workers that regularly leave the nest in order to gather food sources, which include bits of wood, plant stems, and any material containing the plant compound known as cellulose. Subterranean termites are highly dependent on moisture in order to survive, and exposure to the dry outside air results in rapid desiccation and death. In order for workers to access above ground structural wood within homes, they construct air tight mud tubes that protrude from the ground and up foundation walls where they penetrate narrow cracks in order to make contact with indoor structural wood. Virtually all subterranean termite infestations see workers access the substructural wood components located nearest to the ground, or within crawl spaces.

Unlike slab-on-ground homes, crawl space homes allow pest control professionals to gain a clear view of the substructural wood components that are most vulnerable to subterranean termite attacks. However, crawl spaces are perfectly designed to trap moisture that rises from the ground, and inadequate ventilation within crawl spaces prevents moisture from escaping. Since subterranean termite workers are attracted to moist conditions, it is tremendously important for homeowners to avoid moisture buildup in their crawl space. In order to prevent subterranean termite infestations, building codes require all structural wood components within a home to be elevated at least 18 inches from the ground surface where wood cannot be readily accessed by workers. To avoid moisture buildup beneath a home, crawl space openings should not be blocked by objects like stacked firewood or vegetation; instead, it is recommended that vegetation be located at least one foot away from a home’s exterior walls to allow for proper ventilation. Clogged gutters, inadequate downspouts, and inward sloping ground allows rainwater to regularly flood into crawl spaces, which greatly contributes to moisture retention within substructural wood components. All drainage issues should be corrected, as well as plumbing leaks, and placing a vinyl or plastic sheath over crawl space soil provides a vapor barrier that can help to keep structural wood dry. The relative humidity in crawl spaces should be kept at 55 percent, but if crawl space humidity exceeds this number, a dehumidifier will rapidly decrease humidity levels in crawl spaces.

Have you ever measured the relative humidity in your crawl space?