Termites don’t always announce themselves. They can nest inside your home’s walls, under floors, or in the soil beneath the foundation for months or even years before you notice any damage. The type of nest you’re dealing with depends on the species, and knowing the difference shapes how you find it and how it gets treated.
Subterranean vs. Drywood Nests
The two most common types of termites in homes build very different nests. Subterranean termites live in the soil and travel up into your house to feed, constructing mud tubes along foundations and walls to stay protected and moist. Most subterranean species don’t build a distinct nest structure inside the house itself. The exception is the Formosan subterranean termite, which builds “carton nests” inside walls. These are honeycombed masses made of chewed wood, saliva, and feces that retain moisture and can sustain the colony without constant soil contact. An active carton nest feels damp and pliable; an abandoned one dries to a concrete-like hardness.
Drywood termites take a completely different approach. They nest entirely above ground, inside the dry wood they’re eating. There’s no soil connection and no mud tubes. They carve out chambers and tunnels that cut across the wood grain, and some of those chambers get packed with their fecal pellets. These pellets are small, uniform, and distinctively six-sided. If you find a pile of what looks like fine sand or sawdust on a windowsill, countertop, or floor, it’s likely drywood termite frass pushed out through tiny “kick-out holes” in the wood surface.
Where Termites Nest Inside a Home
Subterranean termites almost always enter through wood that’s close to or touching the soil: porches, steps, terraces, fence connections, and planters attached to the house. They can also slip through cracks in the foundation, gaps in concrete floors, and even the hollow centers of cinder blocks. Once inside, they’re drawn to moisture. Wood near sinks, toilets, and leaking pipes is a prime target, as is any lumber kept damp by roof runoff or poor gutter drainage. Air conditioning condensers and condensation from pipes also create the wet conditions subterranean termites need.
In some cases, subterranean termites establish isolated above-ground infestations when they find a reliable water source inside the structure, like a leaking roof or sweating pipes. These infestations can survive without soil contact indefinitely as long as moisture is present.
Drywood termites are less predictable because they don’t need moisture or soil. They nest in structural lumber, window frames, door frames, attic rafters, and any exposed dry wood. Because they live entirely inside the wood they’re consuming, infestations can be deep within walls with no external clue except those pellet piles.
Signs of an Active Nest
The visible signs depend on which species is present, but several clues apply broadly.
- Mud tubes on walls or foundations: Pencil-width tubes of dried dirt running along surfaces are the signature of subterranean termites traveling between soil and wood.
- Pinholes in walls or ceilings: BB-sized spots of dried mud on drywall, paneling, or ceilings appear when termites accidentally break through to the surface and quickly patch the hole with mud. They avoid exposure to open air.
- Six-sided pellets: Small, uniform pellets with six flattened sides collecting on horizontal surfaces indicate drywood termites pushing frass out of kick-out holes.
- Sunken lines in paint or wallpaper: Termites eat the cardboard facing of drywall without disturbing the thin paint layer on top. This creates narrow, winding depressions or trails just beneath the surface.
- Galleries with dried dirt: If you break open damaged wood and find hollowed-out tunnels packed with soil or dried mud, that’s subterranean termite damage. Their feeding follows the wood grain, eating the softer spring growth and leaving the harder layers intact.
- Swarm castles: Formosan termites sometimes build visible nest protrusions on interior walls. These can be just a few inches wide, protruding an inch or two from the wall surface.
Termites also tunnel through materials they don’t eat. They won’t consume gypsum in drywall or sprayed-on foam insulation, but they’ll readily bore through both to reach wood behind them.
How Professionals Find Hidden Nests
Traditional inspections rely on tapping tools and moisture meters, but thermal imaging has become a powerful option for locating nests hidden inside walls. Termites actively regulate the temperature and humidity of their galleries, and that temperature difference shows up on a thermal camera. Depending on the season, a nest can appear as a warm spot in winter or a cool spot in summer. Thermal cameras can detect low-level infestations earlier than visual methods, and they let inspectors scan hard-to-reach areas like high ceilings without tearing anything apart.
That said, thermal imaging identifies areas of concern rather than confirming a species. It’s typically followed by physical inspection or probing of flagged spots to confirm what’s actually there.
Getting Rid of an Active Nest
Treatment depends on whether the colony is underground, inside walls, or in isolated dry wood.
For subterranean termites, liquid termiticide applied to the soil around and beneath the foundation creates a chemical barrier that kills termites on contact as they travel between the nest and the house. This approach works relatively fast once the barrier is in place. Bait stations are the other main option: plastic stations installed in the ground around the home contain a slow-acting substance that termites carry back to their colony. Within weeks of eating the bait, termites die when they try to molt. The catch is that weeks or months may pass before termites even find the bait underground and share it with nestmates. Full colony elimination through baiting can take several months, and some feeding damage continues in the meantime.
Drywood termite nests, because they’re contained inside the wood, are sometimes treated with localized methods. Small infestations can be addressed by injecting treatment directly into the affected wood. Widespread drywood infestations may require whole-structure fumigation, where the home is tented and filled with gas that penetrates all the wood in the structure.
For Formosan carton nests inside walls, treatment usually involves opening the wall to remove the nest physically, then applying termiticide to the surrounding area. Because Formosan colonies can be enormous (millions of individuals), partial treatment often fails.
Why Moisture Control Matters
Every species of termite depends on moisture to some degree, and subterranean termites are especially vulnerable to drying out. This makes moisture management one of the most effective long-term defenses. Fix leaking pipes and faucets promptly. Make sure gutters direct water away from the foundation. Ensure crawl spaces have adequate ventilation. Move mulch and soil away from wood siding. Eliminate any wood-to-soil contact at porches, decks, and steps.
Even drywood termites, which tolerate drier conditions, are more likely to establish in wood that has absorbed some moisture. Keeping attic spaces ventilated and sealing cracks around window and door frames reduces entry points and makes the wood less hospitable. None of this replaces professional treatment for an active infestation, but it changes the odds of getting one in the first place.