Field guide

The Complete Guide to Identifying Termite Damage

Termite damage usually shows up in four ways. Pencil-width mud tubes climb foundation walls and crawl-space joists. Wood sounds hollow when you tap it, and breaking it open reveals soil-lined tunnels inside. Floors sag or feel spongy underfoot. Paint bubbles or blisters over trim and baseboards. Eastern subterranean termites, the species we find across Southern Indiana, hollow wood along the grain, so a board can look completely intact from the outside while the inside is eaten away.

Broken mud tube on a foundation wall showing the hollow channel inside.

Mud tubes: the clearest early sign

Branching termite mud tubes on a poured concrete basement wall.

A mud tube looks like a pencil-width line of dried dirt running up a wall. Earth-colored, slightly rough, roughly 1/4 inch to about 1 inch across. Termites build them from soil packed together with saliva. The material sets hard enough to hold its shape but crumbles under a fingernail.

Here is the part most homeowners never get told: the tube exists because the termite cannot survive the trip without it. Eastern subterranean termites live in the soil, not in your wood. They dry out fast in open air. So they build a covered highway that keeps their own humidity around them while they travel between the colony below ground and the wood above it. Purdue Extension entomologists and Mississippi State Extension both describe the tube the same way, as a shelter tube. Without that cover they will not cross open concrete.

That is also why tubes show up where they do. Look up foundation walls and piers, on the exterior and the interior. Check crawl-space joists and sill plates. Check the inside face of block walls in a basement. Indoors, tubes hide behind baseboards and in the seam where trim meets the floor.

Southern Indiana gives them a lot to work with. Crawl spaces and block basements are common here, and the soil under them stays damp most of the year. That moisture is exactly what subterranean termites in Indiana need.

Take a flashlight into the crawl space. Run the beam along the top of the foundation wall where it meets the wood. Tubes stand out against poured concrete once you know the shape.

What termite-damaged wood looks like

Tap along a baseboard or a floor joist with the handle of a screwdriver. Sound wood answers solid. Damaged wood answers hollow, or papery, like knocking on an empty box. Work your way down the run. The pitch changes right where the damage starts.

That test works because of how termites eat. They work from the inside out. The surface stays put while the interior goes, so a beam can look perfect and be a shell.

Break a piece open and the pattern tells you the rest. Galleries run with the grain, not across it. Termites follow the soft spring wood and leave the hard grain lines standing, so the inside looks layered, almost like a honeycomb pressed flat. On subterranean termites those galleries are lined and spotted with soil and mud. That is the single most useful tell you have.

The surface gives you signs too, if you press on it. Thin outer layers flake or crumble under light thumb pressure, because termites eat right up to the paint film and stop, so what is left is often no thicker than a business card. Paint blisters or bubbles over trim, casing, and baseboards. Trim or drywall looks water-stained with no water source above it or behind it. Subfloor sags or feels spongy when you walk it, especially near an exterior wall or a bathroom.

Take your time with it. Most of this damage sits in places nobody looks: under carpet edges, behind furniture, inside a crawl space. It goes unnoticed for years because nothing on the outside changes.

Termite-damaged floor joist with layered soil-lined galleries following the grain.

The other warning signs

Swarmers and discarded wings. Every spring, Southern Indiana colonies send out reproductives. They fly on a warm day, often right after a rain. You may never see the insects at all. You will find the wings: small piles of them, all the same length, on windowsills and in spider webs. Swarmers indoors mean a colony is already established in or under the structure, and that it has been there long enough to reproduce. Most people call them flying ants. A termite swarmer has a straight waist, straight antennae, and four wings of equal length. An ant has a pinched waist and shorter back wings.

Sagging or spongy floors. Walk the room slowly, near exterior walls and bathrooms especially. A floor over a damaged joist gives a little underfoot. Other spots sound hollow when you step on them.

Doors and windows that suddenly stick. Hollowed framing shifts under load. Termite activity also carries moisture into the wood, and wood swells as it takes moisture on. A door that closed fine last spring and drags now is worth a second look.

Frass. Frass is termite droppings. Drywood termites push it out of the wood in visible pellet piles. Subterranean termites, the species we have here, do not. They pack their waste back into the galleries along with soil. So no frass on your floor tells you nothing, and it is not a reason to rule termites out.

Or let us test it for you, at no cost. Call (812) 401-1028 and we will show you what we find.

How to test whether the colony is still active

The break-the-tube test. Find a mud tube you can reach. Break out a section about an inch long from the middle of the run, not the end, and not where the tube meets the wood. Leave the two ends intact. Then leave it alone and check back in a day or two. If the gap has been sealed back over, the colony is actively using that run. The other direct confirmation is what you see when you open it up: pale, soft-bodied workers inside means feeding is happening right there.

A tube that stays open does not mean you are clear. This is where homeowners get it wrong. Termites abandon runs and reroute constantly. They may simply be feeding somewhere else on the same structure and never come back to the tube you broke. Old dry tubes left over from a colony that was treated or died out are common in older homes here.

The test has a hard limit. It tells you whether that one run is active. It tells you nothing about how many colonies you have, how far the damage has spread inside the framing, or whether anything structural is compromised. That takes someone opening up the crawl space and reading the whole structure. If you are still working out whether you have termites, treat the tube test as one data point, not an answer.

Telling these three apart is what an inspection is for, and ours costs nothing. Call (812) 401-1028 and we will show you what we find before anything is quoted.

Termite damage, water damage, or carpenter ants

Termite galleries are packed with soil. Open infested wood and the tunnels look streaked with mud and dirt, running with the grain. The soil is the tell. Subterranean termites carry the ground up into the wood with them.

Carpenter ant galleries are clean. They look smooth, almost sanded. Ants excavate wood to nest in it rather than eat it, so they push the debris back out. Below the damage you find coarse shavings, like sawdust, mixed with insect parts. No mud, no streaking.

Water damage reads differently. The wood darkens and softens uniformly. There is often a musty smell and fungal growth on the face of the board. No galleries. No soil.

In the real world these overlap. In Southern Indiana crawl spaces, moisture problems and termites travel together, because the moisture is what made the wood attractive in the first place. Finding water damage does not rule termites out. It usually means you should look harder.

Here is where self-diagnosis honestly ends. You can confirm the signs yourself. Scoping the extent inside framing, sill plates and the crawl space is a different job, and it takes a termite inspection to do it right. If you think you have termites, do not wait. The earlier it is caught, the less there is to repair, and the lower the termite treatment cost tends to run.

One more honest note. Most homeowners insurance does not cover termite damage, because insurers treat it as preventable maintenance rather than sudden accidental loss. Check your own policy.

Repair and termite control and prevention get planned off what the inspection actually finds, not off a package chosen in advance.

A termite inspection here is free and it comes with something unusual. K9 Detections runs a termite dog we have access to, so the verdict on a colony does not have to be ours. Call (812) 401-1028.

Pile of fine sawdust-like carpenter ant frass below a baseboard gap.

Frequently asked questions

What does termite damage actually look like?

Wood that sounds hollow when you tap it, with soil-lined tunnels running along the grain inside. Paint that blisters, trim that warps, floors that feel spongy, doors that suddenly stick. The surface often looks fine while the inside is gone.

What are those mud tubes I am seeing?

Pencil-width earth-colored tunnels running up foundation walls, crawl-space joists, and sill plates. Subterranean termites build them from soil and saliva to keep moist on the trip between the ground and your wood.

How do I test if the colony is still active?

Break a one-inch section out of the middle of a tube and check back in a day or two. Rebuilt tube or pale workers moving through it means active feeding. It tells you activity, not how far the damage runs.

Is this termite damage or just water damage?

Water damage darkens and softens wood evenly, and there is usually a leak above it. Termite galleries follow the grain and carry soil packed inside. If you find dirt in the tunnels, it is termites.

Do I have termites or just flying ants?

Check three things. Termite swarmers have a straight thick waist, straight beaded antennae, and four wings of equal length. Flying ants have a pinched waist, elbowed antennae, and front wings longer than the back pair.

Does my homeowners insurance cover termite damage?

Generally no. Insurers treat termite damage as preventable maintenance rather than sudden accidental loss, so most policies exclude it. Read your own policy or call your agent to be sure.

Zach Krietemeyer

Owner

When self-diagnosis ends

Tapping wood and breaking a tube tells you something is there, not how far it has gone. That takes an inspection. Ours is free, and we show you exactly what we find before anything is quoted. Our termite inspection checklist covers what we look at.

Zach holds the state's 7B termite license. He still likes to take the first visit himself, because he wants to see the problem with his own eyes. When he cannot get there, it is Dylan, our General Manager, or one of the crew, working the same way.

Termite work is not covered by the 30-day warranty, which applies to bed bug treatments. It carries something a warranty cannot give you: independent proof. K9 Detections runs a termite dog we have access to, so whether the colony is finished is not our call to make. Ongoing protection runs on a schedule, and callbacks between visits are free on a quarterly or monthly plan.

Serving Evansville and Southern Indiana since 2020, licensed and insured. Call (812) 401-1028.

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