All termite species can be divided into three separate groups known as subterranean, drywood and dampwood termites. As their name suggests, subterranean termites dwell below the ground where workers regularly leave their nest in order to locate food sources. While workers forage through soil, they often stumble upon the base of timber-framed houses located in residential areas. Subterranean termites rely heavily on the constant hydration they receive from moist soil, and exposure to the dry outside air will cause them to dessicate and die. In order to safely access above ground structural wood within homes, workers build airtight “shelter tubes” that connect the moist ground soil with indoor structural wood sources.
Although shelter tubes allow subterranean termites to return to the moist soil whenever they require hydration, subterranean termites generally avoid infesting dry structural wood that is bereft of moisture; instead, subterranean termites prefer to infest structural wood with at least a 20 percent moisture content. During termite inspections, licensed professionals carry a moisture meter, which they use to measure the moisture content of structural wood components. Moisture meters can also be used to measure the moisture content of joists, sills, rafters and other irregularly shaped pieces of wood that are commonly damaged by subterranean termites. Many moisture meters work by inserting pins into wood in order to generate moisture readings, but some meters can remotely measure the moisture content of wood without having to inflict pinholes.
Moisture meters are also useful for gauging the moisture content of the surrounding air. In homes where no moisture problems exist, the moisture content within heated living areas should be between 5 and 10 percent, and between 12 and 19 percent in unheated areas, such as crawl spaces. Moisture readings above 20 percent make homes vulnerable to subterranean termite infestations, and a thorough inspection of wood should be carried out in all indoor areas where moisture levels exceed this figure. In some cases, wood that has become excessively moist must be replaced, and in other cases, setting up a dehumidifier within high-moisture areas within a home can effectively reduce moisture levels. Unusually high moisture levels within homes are often caused by plumbing leaks, improper outdoor drainage systems and rainwater leaks.
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