Termites cause an estimated $5 billion in damage to U.S. homes every year, and the average homeowner who discovers an infestation spends around $3,000 on repairs. The challenge is that termites work silently inside walls, foundations, and framing for months or years before anyone notices. Understanding what to look for, how these insects get in, and what keeps them out can save you thousands of dollars and years of structural headaches.
Types of Termites That Infest Houses
Three main groups of termites target residential structures, and each one behaves differently.
Subterranean termites are the most common and destructive. They build colonies in the soil, sometimes several feet below the surface, and reach your house by tunneling through the ground and constructing mud shelter tubes up foundation walls. They prefer wood that’s already started to decay, because fungi in rotting wood break down cellulose into smaller pieces that are easier to digest. When they feed on sound wood, they follow the grain, eating the softer layers and leaving the harder wood behind. A mature colony can hold anywhere from 60,000 to over one million workers.
Drywood termites skip the soil entirely. They nest inside the dry, sound wood they’re eating, whether that’s structural lumber, dead tree limbs, utility poles, fences, or furniture. They need very little moisture and can survive even in desert climates. Unlike subterranean termites, drywood termites cut across the wood grain, leaving behind a distinctive pattern of chambers and tunnels, some packed with tiny fecal pellets.
Dampwood termites need consistently moist wood. They’re most common in cool, humid coastal areas and typically infest stumps, fallen trees, or structural wood that stays wet from soil contact or a water leak. They carve out large, open galleries inside the wood where they live and feed. If your house has dampwood termites, there’s almost certainly a moisture problem driving the infestation.
How Termites Get Into Your House
The single biggest risk factor is wood touching soil. When siding, door frames, porch posts, or lattice panels sit directly on the ground, termites get a straight path from their colony into your structure with no exposure to open air. Building guidelines recommend keeping all wood components at least six inches above ground level.
Moisture is the second invitation. Subterranean termites need soil moisture levels above roughly 15 percent to thrive, so anything that keeps the ground near your foundation wet makes your home more attractive. Leaking pipes, poorly aimed sprinklers, clogged gutters, and ground that slopes toward the house rather than away from it all create the damp conditions termites seek. Once the soil is moist enough, workers build mud tubes up the foundation and enter through cracks as narrow as 1/32 of an inch.
Firewood stacked against the house, cardboard boxes stored in crawl spaces, old stumps left in the yard, and dense vines growing on exterior walls all give termites food and cover right next to your structure. They can feed on these materials and then bridge into the building itself, sometimes bypassing soil treatments entirely.
Signs of a Termite Infestation
Most termite damage is hidden, but the insects leave several telltale clues on the surface.
- Mud shelter tubes. These pencil-width tunnels of dried mud run up foundation walls, support piers, or plumbing pipes. If you find one, break off a one-inch section and check back in a few days. Active termites will repair the gap.
- Swarmers or discarded wings. Winged termites emerging from walls, ceilings, or floors, or piles of shed wings on windowsills, indicate a colony living inside or very near the structure. Large numbers of swarmers indoors are a serious warning sign.
- Pinholes in drywall or paneling. Tiny, BB-sized spots of dried mud on interior walls or ceilings appear when termites accidentally cut through the surface and then patch the hole from inside.
- Sunken or wavy lines in paint or wallpaper. These indicate feeding galleries just beneath the surface of the wall.
- Fecal pellets. Small, uniform, six-sided pellets accumulating on a floor or countertop are the hallmark of drywood termites. They push these dry pellets out of “kick-out holes” in the wood.
- Swarm castles. Odd, mud formations sprouting from walls or ceilings in late spring signal Formosan termites preparing to release swarmers. Finding mud tubes high on exterior walls or along the soffit is also a sign of Formosan activity.
How Fast Termites Damage a House
Termite damage is slow but relentless. A typical subterranean colony of about 60,000 workers consumes roughly one linear foot of a standard two-by-four pine board every three months, or about one-fifth of an ounce of wood per day. That daily consumption is spread across multiple feeding sites throughout a structure, so visible collapse never happens in weeks or even months.
Research from Penn State University suggests it can take up to 10 years for an infestation to cause serious structural damage to a home. That timeline gives homeowners a real window to catch the problem early. But it narrows dramatically with Formosan termites, an aggressive species common in warmer regions. Formosan colonies can consume structural timber up to five times faster than native subterranean species, compressing that damage timeline significantly.
Professional Inspection: What to Expect
A standard termite inspection covers the exterior foundation, all wood-soil contact points, crawl spaces, basements, garages, attics, and exposed framing. Inspectors use moisture meters, borescopes, and sometimes infrared cameras to find activity hidden behind walls. The whole process takes 45 minutes to three hours depending on the size and complexity of the home.
For a single-family home under 2,000 square feet with no suspected infestation, inspection fees typically run $75 to $150. Real estate transactions require a licensed wood-destroying organism (WDO) inspection, which costs $100 to $200. In high-volume states like California, Texas, and Florida, those fees cluster between $125 and $175. Larger or more complex properties can run $200 to $400, and standalone damage assessment reports for insurance or legal purposes cost $300 to $600. If you enroll in an annual inspection program, most companies offer a 20 to 30 percent discount per visit.
Treatment Methods
Professional termite control relies on two main approaches, sometimes used together.
Liquid Soil Treatments
A liquid termiticide is mixed with water and applied to the soil directly under and around the foundation, creating a chemical barrier that kills or repels termites trying to tunnel through. For new construction, this is done in two steps: a horizontal barrier beneath the slab before it’s poured, and a vertical barrier around the exterior foundation afterward. For existing homes, the treatment involves trenching or drilling along the foundation perimeter and injecting the product into the soil. A well-applied liquid treatment can last 8 to 12 years or longer.
Baiting Systems
In-ground bait stations are installed at regular intervals around the outside of the building. Each station contains wood or another cellulose material laced with a slow-acting insecticide. Foraging workers find the bait, feed on it, and carry the poison back to the colony where it spreads through shared feeding to other workers, immatures, and reproductive members. Baiting is slower than liquid treatment, but it ultimately destroys the colony rather than just blocking its path. Stations require ongoing monitoring and maintenance to stay effective.
For drywood termites infesting a large portion of a structure, whole-house fumigation (tenting) is sometimes the only practical option. The entire building is sealed and filled with gas that penetrates all wood to kill termites throughout. This approach is more disruptive, requiring you to vacate the house for two to three days, but it reaches colonies that spot treatments can’t.
Prevention Steps You Can Take Now
Keep all wood at least six inches above the soil line. That includes siding, door frames, window frames, deck posts, and decorative lattice. If soil or mulch has built up against your foundation over the years, pull it back. Support wooden steps and porch posts on concrete bases rather than setting them directly in the ground.
Control moisture aggressively. Make sure gutters and downspouts move water well away from the foundation. Fix leaking faucets, pipes, and air conditioning units promptly. Grade the soil around your home so surface water flows away from the building rather than pooling against it. If your crawl space stays humid, ensure it has adequate ventilation (one square foot of vent opening per 150 square feet of crawl space, or per 300 to 500 square feet if you have a vapor barrier). Installing polyethylene sheeting over about 75 percent of the crawl space floor further reduces ground moisture.
Never stack firewood, lumber, or cardboard against the foundation or inside a crawl space. Remove old stumps and dead roots near the building. Trim back vines and dense plantings that touch exterior walls. Use mulch sparingly, no more than a couple of inches deep, and keep it from contacting any wood siding or framing around doors and windows.