Claudette Reichel | 1/5/2007 10:31:45 PM
Use multiple methods to make your home resistant to damage from termites, especially Formosan subterranean termites, and other wood-destroying insects. Formosan termites can cause major structural damage within a year of infestation, so if they have been found in your area, it is wise to invest in additional or full protection. Since basic controls and most state-approved stand-alone treatments are not fool-proof, it’s wise to invest in a second line of defense or even a totally termite-resistant structure (no untreated wood or foam in the structural shell of the house or even throughout the entire house).
Basic controls: Make sure that no untreated wood, such as concrete forms, is left in the soil after the foundation is completed. Do not use foam insulation in or near ground contact; termites and carpenter ants can tunnel through it undetected. Termites are attracted to and sustained by wet materials, so moisture-managed construction techniques are essential to prevent both decay and termite damage.
In addition, make sure that your home is designed and constructed to allow for termite inspections and to prevent or shield hidden pathways (including porches, decks and their supports, garage, etc.) Leave an 8-inch clearance between cladding and finished grade so that future termite tunnels are visible, even if mulch is added to the soil. Keep plantings a minimum of 3 feet from the foundation. Use metal flashing caps or termite shields between raised foundations and framing to force termites to reveal themselves or their tunnels.
Soil Treatment: In chemical soil treatments, the soil beneath and around a building should be professionally treated with a labeled termiticide before adding slabs and piers, and a perimeter treatment should be performed within 12 months. The soil is treated with a liquid termiticide under and around a structure to create a continuous chemical barrier that blocks potential routes of termite entry. If the chemical barrier is broken, such as from soil disturbance during construction or walking on it, termites could enter through those gaps. The chemicals approved for use may last from 5 years to15 years; choose the longest-lasting treatment available.
Steel mesh barrier system: A common hidden entry point for termites is through plumbing penetrations in a slab and mortar or other joints in foundations. Termites can go through 0.03-inch cracks. Conventional sealants and membranes are not reliable barriers, since Formosan subterranean termites are known to chew through many non-cellulosic materials they do not eat, including foam insulation, mortar, plastic, rubber and others.
A flexible stainless steel mesh can be cut, shaped and bonded on site by trained installers to provide effective and permanent termite barriers around plumbing holes, in expansion joints, over stemwall and pier foundation perimeters, and other areas. When installed on a raised foundation, the mesh should extend through the cladding to force termites behind the foundation finish where they will reveal themselves.
Borates are toxic to insects and decay fungi but not humans. Termites begin to feed on borate-treated wood products, then die and not form tunnels on the treated wood. Borate pressure treated lumber and wood products manufactured with borates (plywood, engineered woods, cellulose insulation) can be used in framing but should not be used outdoors or in ground contact. The borates can leach out in flowing water or the ground. Normal fasteners can be used in borate-treated woods.
A registered borate barrier system can be spray applied to all structural wood in a 2-foot uninterrupted band from the sill upward and on all wood floor framing. This treatment system is designed to prevent termite tunneling on the wood and as a barrier to prevent access and damage to untreated wood beyond the band. This borate solution also penetrates wood over time but may not always penetrate to the core for total protection. It can be used throughout the structure for added protection.
EPS rigid foam (beadboard) made with borates is available and offers protection from hidden termite tunneling. But until more performance experience is available, the recommendation to have no foam insulation in ground contact applies to all foams, even treated ones, because of the high risk from Formosan subterranean termites.
Copper-based and other pressure treatments of wood (such as ACQ and Copper Azole) are stable, so the wood can be used outdoors and in ground contact. It should be used for wood decks, porches, fencing and other outdoor uses. It is highly resistant to wood-destroying insects and decay. Termites will not feed on the treated wood but will tunnel over it to reach untreated wood. CCA treated wood has been phased out for general use due to concerns about the arsenic it contains.
Termite-resistant materials contain no food for termites and do not provide an easy pathway for them to reach wood and paper. These include treated wood products, concrete, steel, many composites and plastics, fiber cement, brick and stone, borate-containing foam and cellulose insulations, ceramics and glass. Even concrete, steel and pressure treated wood building systems can become infested with termites that find their way to moisture and untreated wood or paper such as untreated wood roof framing over concrete walls, paper in drywall and interior woodwork. Hidden pathways must still be prevented.
Landscape controls are important to protect both your house and trees. Formosan termites eat the core of live trees, which weakens the trees. This has resulted in much tree damage to homes in storms. Choose termite-resistant mulches near your house and trees. Investigate and plant trees near your house that are less likely to become termite infested.
Integrated pest management helps protect homes from termites.
Click here for a Termite Resistance Checklist.