In certain geographic areas, one of the biggest threats to a structure can be termites or other wood destroying insects. Feeding on wood, termites serve an important function in nature by converting dead trees and wood products into organic matter. Unfortunately, the wood in buildings is equally appetizing and termites can cause serious damage to residential and commercial buildings. While there are over several hundred varieties of termites in the world, only four types live in the United States: drywood, dampwood, powderdust and subterranean. Subterranean termites cause 95% of the damage to buildings and are addressed in this article.
Subterranean termites are ground inhabit, social insects, that live in colonies and require moist soil. To protect it from extreme weather conditions, a colony or nest of subterranean termites may be 18-20 feet below the soil surface. A map of the Termite Hazard Distribution, shown in figure 1, shows the area where protection is required. These termites travel through mud tubes to reach food sources above the soil surface. Lumber, wood panels, flooring, drywall, wallpaper, plastics, paper products and fabric made of plant fibers may be damaged in infested buildings. The most serious damage is the loss of structural strength. Other costly losses include: flooring, carpeting, art work, books, clothing, furniture and valuable papers.
The inspection should include exterior and interior surfaces of a foundation, particularly where wood is on or near the soil. Other areas requiring inspections are: wood construction inside basements, crawl spaces, sills, joists, support posts, basement window frames, wood under porches, hollow blocks, and cracks in cement. Termite damage may be located by probing wood with a screwdriver, ice pick or knife. Start an inspection in the basement and use a bright flashlight. Check for the activity of swarmers (winged termites), which are especially common in spring and fall. Look for mud tubes, which are freestanding tubes connecting the soil and wood. Mud tubes are solid evidence of termite activity. Typical mud tubes are shown in the attached photograph.
Evidence of Termite Infestations:
Wood damaged by termites always has the remains of mud tubes attached to wood galleries or tunnels in an irregular pattern. The tunnels may contain broken mud particles with fecal material. In the case of an active colony, white termites may be found in infested wood.
The presence of flying winged males, females or their shed wings inside the building indicates an infestation.
The presence of mud or shelter tubes extending from the ground to woodwork or on foundation walls also may indicate infestation.
Aaron & Wright recommends annual inspections for wood-framed buildings in termite prone areas. The inspection should be conducted by a state-certified termite inspector. If a building appears to be termite infested, a more comprehensive inspection may need to be performed by a structural engineer to render a final opinion of the effect of the termite damage on the superstructure of the building.
Preventive measures can be taken to avoid costly subterranean termite damage. Termite control consists of keeping them in the wild, rather than exterminating them within the building. This is simple in concept, but difficult in practice, since termites can pass through cracks as narrow as 1/32-inch. While termite treatment should be performed by professional pest control operators, following are some of the strategies of termite control:
Sub-slab barriers and chemical treatment prior to installing the foundation on new buildings.
Separating wood structures from the soil.
Plants should be pruned at least six inches from the building.
Wood structures (i.e., fences and decks should not be in contact with the main structure.)
Minimizing cracks in slabs and walls.
Installing barriers to force termites into the open.
Chemical treatment of soils around foundations and/or use of baits.
Keeping the soil, foundation and wood structures dry.
Keep four to six inches of the slab exposed.
Natural control (termite predators).
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