Effective insect resistance requires intervention during the earliest phases of construction.

By Matthew Power

Twenty years ago, most treatment for wood-destroying insects happened long after the builder's departure. Exterminators sprayed gallons of chemicals onto lawns and into wall cavities. Residents had to evacuate while chemicals dissipated.

In recent years, consumers and health organizations increasingly oppose such heavy-handed treatments. But at the same time, imported breeds of voracious insects--such as the Formosan termite--have ravaged homes in many parts of the United States.

"In the Washington area, we've seen termite colonies that are more than a million in size," notes Harold Harlan, senior entomologist with D.C.-based National Pest Management Association. "They can cause extensive damage."

As a result, both home buyers and code officials are leaning on builders to integrate proactive insect deterrents into their new homes.

The modern battle of the bugs can only be won if you do the following:

  • Site the home away from damp, woodsy areas.
  • Remove all cellulose-based materials from the landscape.
  • Design and install gutters and eaves to carry water away from the foundation.
  • At ground level, use physical barriers ranging from low tech (sand) to high tech (stainless steel mesh).
  • Build with borate-treated building materials.
  • When all of the above fail, bring in baiting traps.

Consumers also need to be educated, notes Harlan. "They need to be aware that any continuing moisture problem invites a variety of pests," he says. "Pipes should be insulated, grading should run away from the house. It's all important."
Seven Tips for Successful Bug Obstruction

1. Don't bury debris

Few things attract tunneling insects faster than burying scrap lumber, cardboard, and paper trash on the jobsite. Moisture and cellulose materials provide a perfect food--or nesting medium, depending on the insect. From this base of operations, they can go forth in strength to savage nearby structures.

2. Protect foam board

Below-grade foam makes a great home insulator. But a study by the Urban Pest Control Research Center in Blacksburg, Va., found that even borate-treated expanded polystyrene (EPS) foam panels don't effectively protect against termite invasions. By the time the borate kills them, the foam is devastated. One high-tech remedy: A promising new system called "Termi-Mesh," which can be used to encapsulate the entire foundation in a fine screen of stainless steel (.66 x .45 mm).

3. Add sand barriers

A barrier of uniformly sized sand particles can stop some species of termites. Tests by the U.S. Forest Service found sand more effective in stopping Formosan termites than against native species. Typically, barriers run about 6 inches wide, to the depth of the footer and 6 inches deep under the slab. Particles must be chosen to fit the type of termite threat.

4. Close pathways

Avoid details that allow wood to make direct contact with soil, such as a post penetrating a basement slab. Also, cover any crawl space vent with fine screening. Don't lean wood against the structure during construction.

5. Landscape for drainage

Termites and carpenter ants need moisture to thrive. Ground should slope away from foundation walls. Keep plants a few feet from the home's exterior. Some species hold water in the soil and provide a perfect ladder for insects to reach a home's wooden frame.

6. Deflect runoff

Adding as much as 2 feet to eave overhangs or adding gutters in key roof runoff areas can greatly reduce moisture around the home, at the same time improving the building's elevations. Install gutter guards or easy-cleaning systems.

7. Build with borate

Louisiana-Pacific has introduced a line of products treated with zinc borate or sodium borate, The SmartGuard system includes sheathing, flooring, siding, trim, framing lumber, and cellulose insulation. The company estimates that using it adds roughly $1.50 per square foot to standard construction costs.

After the fact

Once termites have been detected in the home, it's not too late to take action. New baiting systems "may take six or nine months to show results," says Harold Harlan, "but they can be effective." Outdoor and indoor versions of the Sentricon system from Dow AgroSciences can disrupt infestations at both the food source and the colony.