Termite Prevention: What Actually Works

Termite prevention is mostly drainage and carpentry. Keep wood at least 6 inches clear of the soil, move water away from the foundation, pull mulch back from the siding, and get rid of the buried scrap timber and stumps that feed a colony before it ever reaches your house.

That is the honest core of it, and almost none of it involves chemistry.

There is a second half to the answer, though, and the sources I trust most are the ones that insist on it. So it goes near the top rather than buried at the end.

Who this is for

You have not got termites, or you have just had them dealt with and want to keep them out. If you are looking at mud tubes or a pile of wings right now, prevention is the wrong page and the Termite Scan walkthrough will get you to the right one faster.

The measurements

Advice like “keep wood away from soil” is useless without a number attached. These are the published ones, and they do not all agree.

What	Clearance	Source
Wood siding, door and window frames above grade	6 inches	UK extension
Substructural wood beneath the building	12 inches, ideally	UC IPM
Floor joists above exposed ground in a crawl space	18 inches	Model residential code
Wood girders above exposed ground	12 inches	Model residential code
Wood columns above exposed ground	8 inches	Model residential code
Siding above a concrete step, porch or patio slab	2 inches	Model residential code

The code numbers come from the section of the International Residential Code covering protection of wood against decay, which most states adopt with local amendments. Your building department is the authority on which version applies to you.

For mulch, Kentucky’s extension service says apply it sparingly, “a couple inches is usually adequate,” and never let it touch siding or door and window framing. Mississippi State goes further and recommends a mulch-free strip about two feet wide against the foundation, with a rule of thumb worth remembering: if the house sits on a slab, you should be able to see the edge of the slab the whole way round.

Moisture is the part that does the most work

Subterranean termites need moisture, and UC IPM explains why that matters for where they turn up: they nest in or near soil, keep a connection to it, and “because of the moisture requirements of subterranean termites, they are often found in wood that has been slightly decayed.”

Decay is not just a symptom. UC IPM again: “Decayed wood is eaten faster and preferred over sound wood.” Wet wood is easier eating.

So the work is gutters that function, downspouts that discharge away from the wall, irrigation heads that do not spray the foundation, and repairs to leaking pipes and air-conditioning condensate lines. Mississippi State adds a consequence people miss: water pooling against the foundation can “leach, break down or wash away termiticide,” so a drainage problem quietly destroys a treatment you already paid for.

In a crawl space, Kentucky recommends 4 to 6 mil polyethylene sheeting over about 75% of the soil as a vapor barrier.

Ventilation is the one place I found the sources genuinely at odds. Everyone agrees on one square foot of vent per 150 square feet of bare crawlspace floor. Once a vapor barrier goes down, Kentucky says the vent area can often drop to one square foot per 300 to 500, while the model code allows one per 1,500. That is a factor of three to five between two credible sources, and if it matters to your build, the code your county adopted is the one that governs.

The contact points to go and look at

Take a walk round the outside. UC IPM and Kentucky both name the same offenders, and the list is short enough to check in ten minutes: deck posts set straight into dirt, steps or posts embedded in concrete that continues down to soil, form boards left in place after construction, buried scrap lumber, tree stumps, and stucco siding that runs all the way to the ground so termites can travel up behind it unseen.

I have put that walk on one page as a printable termite inspection checklist, so you can tick the contact points off outside instead of trying to hold the list in your head.

Firewood and cardboard against the wall deserve their own mention, because they do something worse than feed termites. Kentucky notes that stacked against a foundation they “may allow termites to bypass surrounding soil treated with a termiticide.” A woodpile can route around a barrier you paid four figures for.

What does not prevent termites

Switching mulch type. Kentucky is unusually direct here, and it kills a piece of advice you will see everywhere: termites are drawn to mulch for its moisture and insulation, “the mulch itself is of poor nutritional quality to termites and a non-preferred source of food,” and so “it makes little difference what type of mulch is used.” Gravel is no better, because it holds moisture in the soil underneath just the same.

Pressure-treated wood, which is not the shield people assume. “Contrary to popular belief, pressure-treated wood is still vulnerable to termite attack; termites often enter the wood through cracks and cut ends, or build tunnels over the surface.”

A termite shield on its own. The model code permits physical barriers, but shields placed on top of a foundation wall count only “if in combination with another method of protection.”

Killing termites you find in the yard. Mississippi State: “It’s neither practical nor possible to try to kill all the termites in your landscape.” A log full of termites twenty feet from the house is termites doing their job in the right place.

Where I have to correct myself

I have said elsewhere on this site that prevention is mostly carpentry and drainage rather than chemistry. Two Tier 1 sources disagree with me, and it would be dishonest to leave that out of the page where it matters most.

Kentucky’s extension service, after listing every structural measure above, adds this:

“Buildings have many natural openings through which termites can enter, most of which are hidden. While the above measures will help make the structure less attractive to termites, the best way to prevent infestation is to protect it with a termiticide.”

Mississippi State is stronger still, recommending that all homes in that state receive a preventive treatment on a regular basis, and telling a homeowner eight years into an untreated house to “go ahead and get this house treated.”

UC IPM is the counterweight. Its prevention guidance is entirely structural, and it recommends no preventive chemical for an uninfested house at all.

Here is what I think is going on, and you can disagree with the reasoning rather than just the conclusion. Kentucky and Mississippi write for the Southeast, where termite pressure is relentless and Formosan termites are established. UC IPM writes for California. Where you live is doing most of the work in that disagreement, and a national answer would be worse than either.

The second thing to notice is the evidence asymmetry. Every efficacy number in the literature is attached to a chemical: termiticides must show five years of control in USDA Forest Service trials to be registered, and Mississippi State reports the better products running 8 to 12 years. Nobody has published a percentage risk reduction for fixing your grading or pulling mulch off the siding. Those measures are universally recommended and nowhere quantified, which is not the same as being ineffective, but it is worth knowing before you treat my framing as settled.

I have also said prevention is cheap. That part is my own reasoning and no extension source prices it, so treat it as a claim about ordinary drainage and carpentry work rather than something I can cite.

What I would actually do

I would do the carpentry and drainage regardless, because it is worth doing for the building anyway. Wet crawl spaces and water against a foundation cause problems that have nothing to do with insects, and you get the termite benefit as a side effect of fixing a house that should not be wet.

On preventive chemical treatment, I would ask where I live. In the Gulf states or the Southeast, the extension services are close to unanimous and I would take that seriously. In a low-pressure area with no history in the building, I would do the structural work, put an inspection on the calendar, and not buy a treatment for a problem I do not have.

If I did buy one, I would want a liquid barrier rather than bait stations, for one specific reason: Mississippi State points out that a properly applied liquid keeps working even if the contract lapses, because the chemical stays in the soil, while bait protection stops when the servicing stops. For prevention, an asset beats a subscription.

And on inspection frequency, the sources split again. UC IPM says every three to five years, and every several years for a house with a history. North Carolina’s agriculture department says annually. If you hold a termite contract, the annual visit is usually already inside the renewal fee you pay, so check before buying it twice.

Sources

• Protecting Your Home Against Termites (ENTFACT-605) — Michael F. Potter, University of Kentucky Department of Entomology, revised March 2026. Accessed 2026-08-04.
• Termite Control: Answers for Homeowners (ENTFACT-604) — Michael F. Potter, University of Kentucky Department of Entomology, revised March 2026. Accessed 2026-08-04.
• Pest Notes: Subterranean and Other Termites (Publication 7415) — UC Statewide IPM Program, content updated May 2014. Accessed 2026-08-04.
• Termites: How to Identify and Control Them — US Environmental Protection Agency, last updated 2025-10-21. Accessed 2026-08-04.
• Common Questions about Termites and Termite Control and Conducive Conditions — Blake Layton, Mississippi State University Extension Service. Neither page carries a printed publication or revision date. Accessed 2026-08-04.
• 3 Tips to Protect Your Home from Termites When Landscaping — Susan Collins-Smith, Mississippi State University Extension Service. No printed date on the page. Accessed 2026-08-04.
• Protection Against Subterranean Termites, and Protection of Wood Against Decay — International Residential Code sections R317 and R318, as adopted by individual states. Numbering differs between adoptions. Accessed 2026-08-04.
• Post-Construction Subterranean Termite Control — North Carolina Department of Agriculture & Consumer Services. No printed date on the page. Accessed 2026-08-04.