Termite barriers are materials that have been specifically designed to prevent subterranean termites from gaining access to a structure. Termite barriers are free of pesticides and act as physical and mechanical impediments to termite foraging activity. Development of physical barriers to effectively exclude subterranean termites have made it possible to add new dimensions to integrated pest management strategies for both new and existing structures. Termite barriers are unique in that, since they contain no pesticides, they are classified as devices by the United States Environmental Protection Agency.
Termite shields are sheet metal fabrications used for decades in light frame construction. Termite shields are often applied underneath wood sill plates. They are designed to force termites to build their mud tubes outside of the structure, where they become visible to a trained pest management professional. (See Termite shield)
Termite membrane barriers consist of elastomeric sealants adhered to a high-strength backing. When included in the building envelope, membrane barriers act as waterproofing, air barrier, and vapor barrier. Applications for termite membranes include on concrete foundation walls, ICF foundation walls insulated concrete forms, under-slab waterproofing, under-sill plates and flooring, and as window, door, and wall flashings, among others. Termite membrane barriers are pesticide-free and act as a physical barrier to water and termite intrusion. Most termite membranes must be implemented during the construction process.
Termite sealant materials are the basic component of termite membranes described above. Sealants are elastomeric, meaning they move with the structure without tearing, and are available in a caulk or spreadable formulation. When caulked around a plumbing penetration in a structure, termite sealant barriers adhere to both the pipe and the concrete. As the structure moves during settling or due to expansive soils, the sealant barrier material maintains a barrier that is impenetrable by termites and other urban pests.
Stainless Steel Screens
Screens with apertures small enough to block termites were developed in Australia and have widely used in the United States, mostly for plumbing penetrations, since the 1990s. One of the early uses of screens for pest exclusion was the implementation of screen doors and window coverings. Screens are required by building codes at vent openings. To exclude rats, screen openings must be ½” (13.7 mm) or smaller. To exclude mice, a screen aperture size of ¼” or smaller is required. Most insects can be excluded with screens measuring 1/16” (1.59mm) in aperture size, but to effectively exclude subterranean termites, required screen apertures measure 1/55” (0.46 mm). Application areas for screens in the building envelope include weep holes, soffits, gable and ridge vents, among others.
Particulate termite barriers have been widely and successfully used in across the world since the 1980s. However, they only became commercially available in the mainland United States in 2013. The principle behind particle barriers has been well researched by Ebeling and Pence (1957), Su et al. (1991), Su and Scheffrahn (1992), Yates et al. (2003), and Keefer et al. (2013). One type of particle barrier is the basaltic termite barrier. These are used in Hawaii, but hardly any place else, because basaltic rock comes from volcano activity, which only takes place in isolated areas of the world. Any hard mineral, such as granite which is used in Australia, will work as a termite barrier if it has all of the requisite properties.
Research with particle barriers began at Texas A&M University in 2003. Various particle characteristics were evaluated, including size, angularity, and interstitial space between particles. This material is generally installed on the perimeter of a home or structure in a wedge formation that measures 4 inches across and 5 inches down, directly against the foundation. Aggregate barriers have also shown success when installed in bath traps or slab leave-outs. During construction and after the foundation is poured, cardboard and other debris is removed from bath trap areas and the particle barrier is installed. Application of this material protects the structure from termite intrusion in a vulnerable area.
One problem with particle barriers is that there are erroneous references on the Web to the use of particle barriers to stop termites. One source says "use a sand barrier". Another says that "16 grit sand is acceptable". Although this loose specification is appreciated by some building contractors who can purchase "sand" or "16 grit sand" very inexpensively at lumberyards and other outlets, it has the effect of damaging the credibility of particle barriers as a termite protection method. All of the research listed above, which took place at universities of California-Berkeley (1956), Hawaii (1982 - 2003), Florida (1992), and Texas A&M (2003 - 2013)pointed to sizes between 8 and 14 as being most effective.
- Geiger, Chris A.; Cox, Caroline. "Pest Prevention by Design" (PDF). San Francisco Environment. Retrieved 23 February 2017.
- Ebeling, Walter; Pence, Roy J. (May 1957). "Relation of Particle Size to the Penetration of Subterranean Termites through Barriers of Sand or Cinders". Journal of Economic Entomology. 50 (5): 690. Retrieved 23 February 2017.
- Su, Nan-Yao; Scheffrahn, Rudolf H.; Ban, Paul M. (1991). "Uniform Size Particle Barrier: A physical exclusion device against subterranean termites (Isoptera: Rhinotermitidae)". Journal of Economic Entomology. 84 (3): 912. Retrieved 24 February 2017.
- Su, Nan-Yao; Scheffrahn, Rudolf H. (1992). "Penetration of sized-particle barriers by field populations of subterranean termites (Isoptera: Rhinotermitidae)". Journal of Economic Entomology. 85 (6): 2275. Retrieved 24 February 2017.
- Keefer, T. Chris; Zollinger, Dan G.; Gold, Roger E. (September 2013). "Evaluation of aggregate particles as a physical barrier to prevent subterranean termite incursion into structures" (PDF). Southwestern Entomologist. 38 (3). Retrieved 23 February 2017.
- Gold, Roger; (October 2015. "Pest Exclusion Using Physical Barriers - Part of the Sustainable Future for New and Existing Structures" (https://www.youtube.com/watch?v=2c2BEFq9Bmk&feature=youtu.be. ' 'Pest World 2015 - National Pest Management Association' '). Retrieved 25 October 2017.
- International Code Council AC 380 "Acceptance Criteria for Termite Physical Barrier Systems" (http://shop.iccsafe.org/ac380-termite-physical-barriers-approved-oct-2014-editorially-revised-feb-2017-pdf-download.html)
- International Code Council ICC Evaluation Report ESR-3632 TERM Barrier System (http://www.icc-es.org/Reports/pdf_files/load_file.cfm?file_type=pdf&file_name=ESR-3632.pdf)
- International Code Council ICC Evaluation Report ESR-1860 Termimesh Termite Control System (http://www.icc-es.org/Reports/pdf_files/load_file.cfm?file_type=pdf&file_name=ESR-1860.pdf)