6 Termite Warning Signs Every Homeowner Should Know

Mud tubes are the most definitive sign of active subterranean termite activity. Subterranean termites live in the soil and must maintain moisture to survive. They build pencil-width tubes of soil, wood particles, and saliva to create protected tunnels from the ground up to the wood they are eating. These tubes run up foundation walls, over concrete footings, and along floor joists in crawlspaces. They are typically 1/4 to 1/2 inch wide and brown or tan in color, resembling a thin line of dried mud. When you see a mud tube, break a small section open. If the tube is active, live termites (small, pale, and white) will be visible inside. An empty tube that is dark and dry may be old and inactive, though termites sometimes abandon and later reuse tubes. Finding a mud tube does not mean the damage is small -- the colony responsible may have dozens of tubes and been active for months or years. Do not spray the tube with consumer pesticide, which will scatter the colony without eliminating it.

Termites eat wood from the inside out, consuming the soft interior cellulose while leaving the outer surface largely intact. A structural member or piece of trim that has been actively fed on will sound hollow when tapped with a screwdriver handle or knuckle. The sound is a dull thud rather than the solid knock of undamaged wood. Run the screwdriver handle along baseboards, door frames, window sills, and floor joists in accessible crawlspaces while tapping. A location that sounds consistently hollow over a span of 12 inches or more likely has termite feeding galleries inside. You can also press a screwdriver point firmly into suspicious wood: healthy wood resists penetration firmly, while termite-damaged wood may give way or crumble. The absence of visible damage on the exterior does not mean the wood is sound. Termites eat along the grain of the wood and can leave a paper-thin shell intact to maintain moisture while the interior is entirely consumed.

Termite swarmers (also called alates) are the reproductive members of a mature termite colony. Once a year, typically in warm and humid conditions following a rain, a colony sends out swarmers to establish new colonies. Subterranean termite swarms in the Eastern US and Midwest typically occur in spring (March through May). Drywood termite swarms in the South and Southwest typically occur in late summer and fall. Swarmers are attracted to light and you may see them swarming around windows, exterior lights, or emerging from cracks in walls and floors. They shed their wings shortly after swarming, so discarded wings near windowsills, along baseboards, or piled on the exterior are a strong indicator of a swarm having occurred, even if you did not witness it. Swarmers themselves are about 1/4 to 3/8 inch long with two pairs of equal-length wings, which distinguishes them from flying ants (whose wings are unequal in length). A swarm does not necessarily mean your structure is actively infested -- swarmers from a neighboring colony may have landed on your property. However, swarmers emerging from inside the home or near the foundation are a definitive sign of an established colony nearby.

Frass is the termite equivalent of sawdust: the tiny pellets that drywood termites push out of their galleries through small kick holes. Drywood termite frass pellets are distinctive: they are 1 millimeter long, six-sided, and wood-colored, ranging from cream to dark brown depending on the wood species being eaten. They are often found in small piles resembling piles of pepper or sand below baseboards, window sills, door frames, or near wooden furniture. Subterranean termites do not produce frass in the same way (they use it to construct their mud galleries), so the presence of frass almost always indicates drywood termites. Finding frass means the infestation is active and the termites are currently feeding. The pile size gives a rough indication of how long the colony has been active: a small tablespoon-sized pile represents months of activity; larger piles may represent years. Frass can be confused with sawdust from boring beetles, but termite frass pellets are distinctively six-sided when viewed under magnification.

Subterranean termites require moisture to survive. As they feed inside walls and flooring, they introduce moisture from the soil into the wood structure. This moisture can cause the paint above infested wood to blister, bubble, or peel in patterns that resemble water damage from a leak. The surface may feel slightly soft when pressed. Wallboard (drywall) over an infested wall may show soft spots, darkening at the base, or subtle bulging. This damage is particularly easy to confuse with water damage from a plumbing leak or roof leak, and homeowners sometimes spend money investigating plumbing before the termite origin is discovered. A key distinction: termite moisture damage typically appears along the base of walls (near the foundation) or along floor-wall joints. Water leak damage typically appears below plumbing fixtures or near roof penetrations. If no leak source can be identified after a thorough inspection, have a pest control professional check for termite activity.

Structural damage from termites is the end stage of a long-running infestation. Floors that feel springy underfoot, doors and windows that no longer fit their frames properly (caused by termite-damaged framing moving), sagging ceilings, or visibly weakened floor joists in a crawlspace all indicate significant structural damage. By the time structural damage is visible, the infestation has typically been present for several years. Repair costs for termite structural damage range from $1,500 to $15,000 or more depending on what needs to be replaced. Unlike the termite treatment itself, structural repair is generally not covered by standard homeowner's insurance (most policies exclude damage from wood-destroying insects). This is why catching termites at the mud tube or frass stage is so important: the cost difference between treating a colony with a liquid barrier ($500 to $1,500) versus treating a colony and repairing structural damage ($5,000 to $20,000) is enormous.