Termite Damage, Treatment, and Prevention: What You Actually Need to Know

What Termites Actually Do to Your House

Termites eat cellulose. That's the structural fiber in wood, cardboard, paper, and even drywall backing. A mature subterranean termite colony of around 300,000 workers can eat about a pound of wood per day. That doesn't sound like much until you realize they've been at it for 3 years before you noticed anything.

They don't eat the surface. They hollow out wood from the inside, following the grain, leaving a paper-thin shell that looks perfectly normal. You can have a floor joist that's 90% hollow and it'll still look fine from the outside. Tap it with a screwdriver handle and it sounds like a drum.

The structural damage isn't hypothetical. I've seen 2x10 floor joists reduced to what looks like a wafer cookie, still holding up a bathroom. The national average repair bill after termite damage runs around $3,000, but I've written estimates over $15,000 for homes where they got into the main beam or load-bearing walls. One house in Houston had the entire garage header sistered because the original was completely consumed.

Here's what most people don't know: termites cause more property damage in the U.S. each year than fires, floods, and tornadoes combined. The USDA puts the number around $5 billion annually. And homeowner's insurance doesn't cover it because it's considered "preventable maintenance."

Subterranean vs Drywood vs Formosan: Why It Matters for Treatment

There are three species groups you'll deal with in the U.S., and knowing which one you have changes everything about how you treat it.

Subterranean Termites

These are the ones in every state except Alaska. They live in the soil and build mud tubes up your foundation to reach wood. A single colony can have 100,000 to a million workers. They need moisture constantly, which is why they stay connected to the ground. If you break their mud tubes, they'll build new ones within days.

Treatment for subterranean termites means creating a chemical barrier in the soil around your foundation or installing bait stations. You can't just spray the wood they're eating because there are a hundred thousand more coming from underground.

Drywood Termites

Drywood termites don't need soil contact. They fly in, find a crack in exposed wood, and set up shop inside the timber itself. You'll find them mostly in coastal states: California, Florida, Texas, Hawaii, the Carolinas. Their colonies are smaller, usually under 10,000, but they're harder to detect because there are no mud tubes. The main sign is frass, which are tiny wood-colored pellets they kick out of small holes in the wood. Looks like someone dumped a pile of coarse sand on your windowsill.

Treatment is completely different. For a localized infestation, a tech can drill into the wood and inject a termiticide like Termidor Dry or use orange oil (d-limonene). For widespread drywood infestations, whole-structure fumigation with Vikane (sulfuryl fluoride) gas is the only option that reaches every pocket.

Formosan Termites

Formosans are a subtype of subterranean termite, but they deserve their own category because they're significantly more destructive. A Formosan colony can hit 5 million workers. They build carton nests inside walls that retain moisture, so they don't always need ground contact once established. They're concentrated in the Gulf Coast states (Louisiana is ground zero), Hawaii, and parts of the Southeast.

If you have Formosans, you need professional treatment. Period. There is no DIY approach that handles a colony this size.

Signs You Have Termites

Most infestations go unnoticed for 3 to 5 years. By the time you see obvious damage, they've been working for a while. Here's what to look for:

Mud tubes. Pencil-width tubes of dried mud running up your foundation wall, along pipes, or in crawl spaces. Break one open. If it's active, you'll see small white insects inside. Even if it looks abandoned, it means they were there, and they may have found another route.

Frass. Drywood termites push their droppings out of tiny kick-out holes. The pellets are about 1mm long, six-sided, and the same color as whatever wood they're eating. If you see a small pile of what looks like fine sawdust under a window frame or near baseboards, that's frass.

Hollow-sounding wood. Knock on door frames, baseboards, and window trim with the butt of a screwdriver. Solid wood makes a solid thud. Termite-damaged wood sounds papery and hollow. Push the screwdriver in. If it sinks with almost no resistance, you've got a problem.

Swarmers. Winged termites that emerge in spring (subterranean) or fall (drywood), usually after rain. They look similar to flying ants but have straight antennae, equal-length wings, and a thick waist. Finding a pile of shed wings on a windowsill means a colony is nearby and mature enough to reproduce.

Bubbling or peeling paint. This happens when subterranean termites eat the wood behind painted surfaces. Moisture from their tunnels causes the paint to blister. It looks like water damage, and plenty of homeowners treat it as a paint problem for years before finding the real cause.

What Treatment Actually Costs

Pest control pricing is all over the place, so here are the real numbers from what companies charge in 2025-2026:

Inspection: A standalone termite inspection runs $75 to $150. Many companies waive this fee if you hire them for treatment. Real estate transaction inspections (WDI reports) are almost always $75 to $125 flat.

Liquid barrier treatment: $3 to $8 per linear foot of foundation. A typical 1,500 sqft house with 150 linear feet of foundation costs $450 to $1,200. The industry standard product is Termidor (fipronil). A treatment lasts 5 to 10 years depending on soil conditions. Cheaper companies use bifenthrin, which works but breaks down faster, usually 3 to 5 years.

Bait stations: $8 to $12 per station, installed every 10 feet around the perimeter. Initial install for that same 1,500 sqft house runs $1,500 to $3,000. The catch is the annual monitoring fee: $250 to $400 per year. Sentricon and Trelona are the two major brands. The bait approach is slower but eliminates the colony rather than just blocking it.

Fumigation (drywoods): $1 to $3 per square foot. A 2,000 sqft home runs $2,000 to $6,000. You'll need to leave your house for 2 to 3 days, remove all food, medicine, plants, and pets. The tent goes over the entire structure. There's no residual protection after fumigation, so re-infestation is possible.

DIY Options: What Works and What Doesn't

Let's be direct about this. Some DIY termite treatments work. Most don't.

Taurus SC (fipronil 9.1%): This is the same active ingredient as Termidor SC, sold at a fraction of the price. A 20oz bottle runs about $35 on Amazon and covers 40 to 80 linear feet of trench. You dig a 6-inch deep trench along your foundation, pour in the diluted solution, and backfill. It works. The hard part is doing it thoroughly. You need to trench every inch of your foundation, including where pipes and wires enter, around porch supports, and along any wood-to-concrete contact points. Miss a 3-foot section and they'll find it.

Borate wood treatment (BoraCare, Timbor): Effective as a preventive on bare wood. You brush or spray it on exposed framing, floor joists, and sill plates. It penetrates the wood and makes it toxic to termites for decades. The limitation: it doesn't work on painted or sealed surfaces, and it won't kill termites already inside the wood. Best used during new construction or renovation when framing is exposed.

Orange oil (d-limonene): This gets marketed heavily in California for drywood termites. Here's the truth: it works on contact, but only in the specific gallery you inject it into. Drywood termites can have multiple colonies in different parts of the same house. Orange oil treatment misses the ones you can't reach. Studies from UC Davis showed a 50-60% success rate for localized treatment. That means a coin flip. If you have drywood termites in one piece of trim, maybe. If they're in your attic framing, don't bother.

Cardboard traps, nematodes, diatomaceous earth: None of these will stop an active infestation. Cardboard traps might catch a few foragers. Nematodes need perfect soil conditions. DE doesn't reach where termites live. Save your money.

Prevention That Actually Matters

Termite prevention comes down to two things: eliminate moisture and eliminate wood-to-soil contact.

Fix leaky faucets, running toilets, and dripping AC condensate lines. Subterranean termites need water. A chronic drip next to your foundation is an invitation. I've seen more infestations start under bathrooms with slow leaks than anywhere else in a house.

Keep mulch 6 inches away from your foundation. Wood mulch doesn't attract termites directly, but it holds moisture against the foundation and gives them cover. Use gravel or rubber mulch within that 6-inch zone.

No wood should touch soil. Fence posts, deck supports, porch columns, and stair stringers that sit directly on or in the ground are highways for termites. Use metal post brackets or concrete footings. Check your siding. If it extends below the top of your foundation, they can get behind it without building visible mud tubes.

Store firewood at least 20 feet from your house and off the ground.

Get an annual termite inspection. Not a general pest inspection -- a specific termite inspection where someone checks the crawl space, garage, and attic. In high-risk states (Texas, Florida, Louisiana, California, Georgia, the Carolinas), this isn't optional. Most companies offer a free annual inspection if you're on a bait station or retreatment warranty plan. Not sure how to pick a good company? Our guide to choosing a pest control company walks through what to look for.

When You Need a Professional

Call a pro if you find active mud tubes, structural damage, or swarmers inside your home. Those mean an established colony. A bottle of Taurus SC and a weekend of trenching might handle a minor perimeter issue, but if they're already inside your walls, you need a full treatment plan with monitoring.

Call a pro for drywood termites. Localized injection treatment requires a thermal camera or microwave detection equipment to find all the colonies. Fumigation requires a licensed applicator by law.

Formosan termites? Don't even think about DIY. Call someone today.

You can wait if you found a single, old, inactive mud tube on an exterior wall with no signs of active feeding. Monitor it. Check it weekly. If you see fresh mud, it's time to treat.