What are the building code requirements for making a house termite resistant?
Friday, June 14, 2019
The Residential Edition of The Florida Building Code devotes a complete section, “R-318 - Protection Against Termites,” to construction details to keep termites from infesting a house. The code attacks the problem in two ways: 1) create a barrier to keep them from getting into the house, and 2) make it easier to spot termites if they do manage to sneak through the barrier. Here’s a summary of each of the strategies:
• Removal of all wood under the house footprint before construction - Any form of cellulose, including even old cardboard boxes on the ground, is termite food. Tree stumps, roots, wood stakes, and lumber scraps left in ground under a home provide sustenance for termites while they search for openings to get to all the wood studs above them.
• Termiticide treatment of ground or base of house - The code allows multiple different ways provide a protective barrier, "including soil applied pesticides, baiting systems, and pesticides applied to wood, or other approved methods of termite protection labeled for use as a preventative treatment to new construction.” The treatment must be done by a licensed pest control company, and they have to issue a statement to the building department that “the building has received a complete treatment for the prevention of subterranean termites. Treatment is in accordance with rules and laws established by the Florida Department of Agriculture and Consumer Services.” A notice to the homeowner is also required to be posted inside the house. It is usually found on the door of the electric panel, and states the type of treatment used, date of treatment, and recommendation to renew contract and inspect annually.
• Eliminating small cracks at ground level where termites can sneak into a home undetected - Sleeves around pipe penetrations of the floor slab must be clamped and cold joints for brick-bearing ledges are not allowed, to eliminate any small gap that a termite can squeeze through. Termites are small and can fit through a crack the thickness of a credit card.
• Keeping water away from the ground under a house - Subterranean termites need moisture to survive and condensate drain lines, gutter terminations, and sprinklers that are too close to the house provide easy access to water for them. So they should be moved a minimum of 1 foot away from the footprint of the house. Also, the site must be graded to slope away from the house.
• Maintaining a six inch gap between any wood siding and the ground - That six inches creates a “no man’s land” that termites have to cross to get from the soil to the wood they want to eat. Because they dry out and die if exposed to open air for even a few minutes, termites have to build a slender mud tube across the code-required gap to crawl through. The mud tubes (shown below) are a sign that they are trying to, or already have, entered your home and immediate action is required.
• Foam insulation sheathing on foundation walls not allowed - The foam provides a concealed pathway for termites to crawl up into the house unnoticed. This requirement applies only in areas where the probability of termite infestation is “very heavy” according to the TIP Zone map. See our blog post What is a TIP Zone Map? for more. All of Florida, by the way, is in the “very heavy” zone.
Wood posts in contact with the ground must be pressure-treated - The chemicals in the wood treatment deter both wood rot and termites. The pressure treatment must be rated for ground contact, which requires a higher dose of chemicals in the wood. This requirement is at R317.1.2.
There are more detailed specifications, and also a number of special exceptions to many of the rules, but these are the key strategies required to be implemented in house construction to keep termites away. Although the Florida code is quoted here, the International Residential Code (IRC) is almost identical.
One old-time requirement that is no longer in the building code is termite shields. Before the modern slab-on-grade construction, when most homes had a raised wood floor on a stem wall or piers, a strip of sheet metal placed between the foundation and floor framing created a formidable termite barrier because the knife-edge of the metal was difficult for them to build a mud tube around. Termite shields are a less-than-perfect solution that termites can find a way around if not meticulously installed, and are still used today by some builders, although not required. To read more about it, go to our blog post What is a termite shield?
Also, see our blog post When do termites swarm in Florida? and I think I have termites. What does a termite look like? and Do termites eat concrete?
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To learn more about termites, see these other blog posts:
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