Termites are active year-round, but most people only notice them during specific moments: a sudden swarm of winged insects near a window, a crumbling baseboard, or mysterious mud tubes running up a foundation wall. U.S. residents spend an estimated $5 billion annually on termite control and repairs, with the average homeowner paying about $3,000 to fix damage once it’s discovered. Understanding what termite activity looks like, what drives it, and how to reduce your risk can save you from becoming part of that statistic.
Signs of Active Termite Infestation
The tricky part about termites isn’t that they’re hard to spot once you know what to look for. It’s that old damage and active damage can look similar. Dried mud in wood galleries, for instance, could be from an infestation that was treated years ago. The key is confirming that termites are still present and working.
Mud tubes are the most recognizable sign of subterranean termite activity. These pencil-width tunnels run along foundation walls, floor joists, or other surfaces, giving termites a protected highway between their underground colony and your wood. To test whether a tube is active, break away a one-inch section and check back over the next few days. If you see termites inside, or if the tube gets repaired, the infestation is active.
Another reliable indicator is what pest control professionals call “pinholes.” These are tiny openings in drywall or wood where termites accidentally broke through to the surface. Because termites avoid exposure to outside air, they quickly patch these holes with mud. If you scrape away a mud-filled pinhole and it reappears within a day or two, termites are actively feeding behind the surface.
Drywood termites leave a different calling card. They push dry fecal pellets out of small “kick-out holes,” creating small piles of what looks like coarse sand or pepper beneath infested wood. These pellet piles on a windowsill, shelf, or floor are a reliable sign of a drywood colony overhead. Subterranean termites, by contrast, don’t produce visible pellets because their waste stays inside the wood or mud tubes.
Swarmers (the winged reproductive termites) are another major signal. Finding a few near an exterior light doesn’t necessarily mean your home is infested, since swarmers travel from neighboring colonies. But large numbers emerging inside a building point to a large, established colony feeding on that structure.
How Different Species Behave
The three main termite groups in the U.S. have distinct habits, and knowing which type you’re dealing with changes where you should look for damage.
Subterranean termites are the most common and destructive. They build nests in the soil and reach wood either through direct ground contact or by constructing mud shelter tubes. Their feeding follows the grain of the wood, targeting the softer spring growth layers while leaving behind the harder wood, which creates a layered, almost honeycomb-like damage pattern. A mature subterranean colony averages around 300,000 individuals, though some reach into the millions. A colony of roughly 60,000 can eat through a foot of standard 2×4 lumber in about five months. That sounds slow, but damage accumulates over years, often hidden inside walls.
Drywood termites nest above ground in relatively dry wood like lumber, utility poles, fences, and dead tree limbs. Their colonies never connect to the soil, which means they don’t build mud tubes. Instead, they enter through exposed wood surfaces and cut across the grain, leaving a pattern of chambers and tunnels, some packed with fecal pellets. Drywood infestations are common in attic framing, window frames, and furniture.
Dampwood termites nest in very moist wood and are most common in cool, humid coastal areas. They need consistently high moisture levels to survive, so they’re rarely a problem in well-maintained structures. Leaking roofs, plumbing failures, and wood in contact with wet soil create the conditions dampwood termites need.
What Attracts Termites to a Structure
Moisture is the single biggest factor. Termites are drawn to consistently damp soil near foundations, and anything that keeps the ground wet increases your risk: clogged gutters, leaking faucets, poorly graded landscaping, and sprinkler systems aimed at the house. Even mulch, which many homeowners assume attracts termites because it’s made of wood, is primarily an attractant because it holds moisture in the underlying soil. The wood in mulch is actually poor nutrition for termites. Stone or pea gravel mulch retains moisture too, so the material matters less than how much you use and where you place it. A couple of inches is plenty, and it should never touch wood siding or door and window frames.
Wood-to-soil contact is the other major vulnerability. When siding, framing, porch steps, or deck posts touch the ground, termites can move directly from soil into the structure with no visible evidence on the outside. Even pressure-treated wood isn’t immune. Termites enter through cracks and cut ends or simply build tunnels over the treated surface. Wood components of a building should sit at least six inches above ground level, and beams in crawl spaces need a minimum of 18 inches of clearance.
Firewood, lumber scraps, cardboard boxes, and newspapers stacked against a foundation create both a food source and a hidden bridge into the building. Stacking firewood well away from the house and removing old stumps and dead roots near the foundation eliminates two easy entry points. Dense plantings like ivy or vines growing directly on the house also give termites concealed access.
Seasonal Patterns and Swarming
Termite colonies feed 365 days a year. There’s no “off season” for damage. However, swarming, the event that makes most people realize they have a problem, is seasonal. Subterranean termites typically swarm during the daytime in spring, often after a warm rain. Formosan subterranean termites swarm in late spring to early summer evenings. Drywood termites tend to swarm in late summer or fall, depending on the region.
Swarming is how a colony reproduces. Winged termites leave the nest, pair off, and attempt to start new colonies. The swarmers themselves don’t cause damage, but their presence inside a building is a diagnostic clue. A handful of swarmers indoors could have drifted in from outside. Dozens or hundreds emerging from a wall, floor, or ceiling mean a colony is already established in the structure.
How Professionals Detect Hidden Activity
Because termites work inside walls, under floors, and behind surfaces, much of an infestation is invisible during a standard visual inspection. Professional inspectors increasingly use thermal imaging cameras to find activity without tearing into walls. Termite digestion releases heat as carbon dioxide, and their mud tubes hold moisture, both of which create irregular temperature patterns on wall surfaces that a thermal camera can pick up. Nests under floorboards or inside walls may show up as distinct hot spots, while tunnels appear as lines of elevated moisture.
Higher-resolution thermal cameras are needed to detect subtler signs like moisture damage patterns that suggest termite pathways. Acoustic detection tools can also pick up the vibrations and head-banging signals termites use to communicate, identifying active colonies behind drywall. These technologies don’t replace a physical inspection, but they help narrow down where to look and reduce the need to cut into walls on a hunch.
Reducing Your Risk
Prevention comes down to eliminating the conditions termites need: moisture, soil contact with wood, and concealed entry points. Start with drainage. Gutters and downspouts should direct water away from the foundation, the ground should slope away from the building on all sides, and any leaking pipes or faucets near the foundation should be repaired. Air conditioning units that drip near the foundation are an overlooked moisture source.
Maintain clearance between soil and wood. The six-inch minimum for exterior woodwork and 18-inch minimum for crawl space beams aren’t arbitrary numbers. They provide enough visible space for an inspector to spot mud tubes before termites reach the structure. Posts or stairs that pass through concrete to reach the soil are vulnerable even if the concrete itself seems solid, since termites travel through gaps invisible to the eye.
Chemical soil barriers remain a standard professional treatment. For existing structures, this involves trenching along all foundation walls to a minimum depth of six inches, and often 30 inches or more down to the footing, then applying termiticide to create a continuous chemical zone termites can’t cross without being exposed. Slab foundations require drilling along cracks and construction joints at 12-inch intervals so the soil beneath can be treated. Baiting systems, which use slow-acting toxicants that termites carry back to the colony, offer an alternative for situations where soil treatment is impractical.
Annual professional inspections are the single most effective way to catch activity before it becomes expensive. Termites can feed for years before visible damage appears, and by the time you notice a soft spot in a floor or a sagging door frame, the colony may have been at work for a long time.