Termites eat wood from the inside out, so an infestation can go unnoticed for months or even years. The most reliable way to tell if termites are in wood is to look for a combination of signs: mud tubes on surfaces, tiny pellet-like droppings, hollow sounds when you tap, and visible damage patterns like shelving or tunneling inside the grain. A single sign is worth investigating, but multiple signs together make a strong case.
Mud Tubes on Foundations and Framing
Subterranean termites, the most common and destructive type in the U.S., build pencil-width tubes out of soil, wood particles, and saliva. These tubes run from the ground up foundation walls, along floor joists, or through cracks between structural members. Their purpose is to protect the colony from open air as workers travel between the soil and the wood they’re feeding on. You can find them hanging from sub-flooring, running along basement walls, or even crossing ceilings if the colony has established itself above ground.
Active tubes feel slightly damp and hold together when touched. Old, abandoned tubes are dry and crumble easily, leaving behind faint etchings on the surface that can remain visible for years. If you break open a section of tube and see small, pale insects inside, the infestation is active. Even if a tube appears empty, termites sometimes rebuild nearby, so an empty tube doesn’t mean the problem is gone.
Frass and Kick-Out Holes
Drywood termites, which live entirely inside the wood rather than in soil, leave behind a different calling card: frass. These are tiny fecal pellets about the size of a grain of sand, hard and dry, with six concave sides that give them a hexagonal shape under magnification. Their color ranges from light tan to dark brown depending on the wood species the termites are consuming.
Unlike subterranean termites, drywood termites push their waste out of small openings called kick-out holes to keep their internal galleries clean. You’ll often notice a small pile of what looks like fine sawdust or sand collecting on a windowsill, floor, or ledge below a wooden surface. The kick-out holes themselves are tiny and easy to miss, but those little mounds of pellets are a clear indicator that termites are actively tunneling inside.
The Tap Test
Because termites consume the interior of wood while leaving the outer surface mostly intact, infested wood often sounds distinctly different when you knock on it. Use the handle of a screwdriver or a small hammer and tap along baseboards, door frames, window frames, and any exposed wood in basements or crawlspaces. Solid, undamaged wood produces a firm, dense sound. Wood that has been hollowed out by termites sounds papery or produces a slight echo.
After tapping, press the tip of a flathead screwdriver into the wood. If it sinks in easily or the surface gives way, the structural integrity has been compromised. Termite-damaged wood sometimes looks perfectly fine on the outside but collapses under light pressure. A flashlight and screwdriver are the two most useful tools for a basic DIY inspection.
Damage Patterns Inside the Wood
When you break open or cut into termite-damaged wood, the internal damage has a distinctive look. Termites create long, thin tunnels and layered tiers that pest professionals call “shelving.” These appear as horizontal or vertical lines of missing material, forming maze-like patterns along baseboards or door frames. The galleries feel rough and ragged, and subterranean termite tunnels are often caked with dried mud.
This is one of the clearest ways to distinguish termite damage from carpenter ant damage. Carpenter ants also tunnel through wood, but their galleries are smooth, clean, and almost polished-looking. Carpenter ants don’t eat the wood; they excavate it. Termites consume the cellulose, leaving behind rough, muddy channels. If you see smooth, sawdust-free tunnels, you’re likely dealing with ants rather than termites.
Termite Damage vs. Wood Rot
Wood rot, caused by fungal decay, can look similar to termite damage at first glance since both weaken and destroy wood. But the texture and pattern differ. Rotted wood becomes spongy and absorbent, eventually drying out and splitting into cube-like chunks. It crumbles easily and often has visible mold or discoloration.
Termite-damaged wood is hollow and weak but breaks off in long, thin pieces rather than crumbling into cubes. The elongated tunnel structure means the wood tends to splinter along the length of the galleries. If you see that characteristic shelving pattern or find mud inside the damaged areas, termites are the cause. Wood rot involves no tunnels, no mud, and no insect evidence.
Swarmers and Shed Wings
Once or twice a year, mature termite colonies release winged reproductive termites called swarmers. These emerge in large numbers, often on warm days after rain, looking for a place to start new colonies. If you see swarmers coming directly out of your walls, ceiling, or floor, that’s definitive proof of an active infestation inside the structure.
Swarmers are roughly half an inch long including their wings. After landing, they shed their wings, and you’ll find small piles of translucent, equal-length wings on windowsills, near light fixtures, or along the floor. Termite wings are all the same size (front and back pairs match), which distinguishes them from flying ants, whose front wings are noticeably longer than their back wings. Finding shed wings indoors, even without seeing the insects themselves, is a strong indicator of a nearby colony.
Where to Focus Your Inspection
Termites follow moisture. The most productive places to check are areas where wood contacts or sits close to soil: foundation sills, porch supports, deck posts, and basement framing. Inside the home, focus on baseboards, door frames, and window frames on the ground floor. In crawlspaces, examine floor joists and any wood within reaching distance of the ground.
Moisture is one of the biggest risk factors. Wood with a moisture content above 20 percent is significantly more vulnerable to both termite attack and fungal decay. Plumbing leaks, poor drainage, and inadequate ventilation in crawlspaces all create conditions termites exploit. If you notice peeling paint, buckling floors, or doors and windows that suddenly stick, these can be indirect signs that wood is swelling from moisture damage or being structurally weakened by feeding.
How Fast Termites Destroy Wood
Termite damage is slow but relentless. A mature subterranean colony of about 60,000 workers can consume one linear foot of a 2×4 board in roughly five months. That sounds modest, but colonies can contain hundreds of thousands of individuals, and most homes have multiple entry points. The damage compounds over years, and because it’s hidden inside walls and framing, it often isn’t discovered until it’s extensive.
When a Professional Inspection Helps
A trained inspector brings tools that go beyond the screwdriver-and-flashlight approach. Moisture meters identify areas of high moisture content in joists, sills, and rafters, flagging zones where termites are most likely feeding. Borescopes, which are fiber-optic cameras threaded through a small drill hole, allow visual inspection inside wall voids to spot tubes, galleries, and nesting material without tearing open drywall. Some inspectors use acoustic detection equipment that amplifies the sound of termites feeding inside wood.
Professional inspections are especially valuable for real estate transactions, for homes in high-risk termite zones, and any time you’ve found one or two signs but can’t confirm the extent of the problem. Many termite warranty contracts include annual reinspections, which catch new activity before it becomes a costly repair.