Most pest signs are ambiguous. A dark speck could be several things, sawdust could be four, a winged insect could be an ant. A mud tube is not ambiguous. An earthen tube about the width of a pencil, running up a foundation wall, a pier or a floor joist, is built by subterranean termites and by nothing else you will find on a Virginia house.
What is still open is whether it is active, and there is a test for that which takes two minutes and a few days of patience.
This is general information. Extent and treatment can only be established by a licensed inspector at the property.
Why they build them at all
Subterranean termites live in soil and eat wood, and they cannot survive the trip between the two in open air — they dry out and they are exposed. So they build a covered road out of soil, saliva and faeces, and travel inside it.
That constraint is the whole reason the sign exists, and it explains everything about where to look. The tube always connects soil to wood. It runs up something, not along nothing.
The species doing it in Virginia is the eastern subterranean termite. Several local companies list the Formosan termite among the state's three species; as of 2026 the nearest established populations are around Wilmington, North Carolina. What Virginia actually has →
Where to look, in order
The outside of the foundation, all the way round, at the point where masonry meets soil. Move mulch and check behind shrubs — the tubes are most often where nobody looks.
Inside the crawl space, on piers, on the interior face of foundation walls, and on the underside of joists and sills. This is where they are found most often, because it is dark, humid and undisturbed.
Where anything wooden touches earth. Deck posts, porch steps, fence rails against the house, buried form boards left behind by the builder.
In a basement, on walls, in corners, behind stored boxes, at the edge of a slab.
Where pipes and wires enter, because a penetration is a ready-made route.
Four kinds of tube, and what each means
| What you see | What it means |
|---|---|
| Working tube — soil to wood, continuous | the main road; the ordinary finding |
| Exploratory tube — going up and stopping in air | they were searching and did not find wood |
| Drop tube — hanging from wood down toward soil | built from above; often means established activity in the timber |
| Swarm castle — short, wide, with openings | built to release winged reproductives, usually in spring |
The last one connects to the other termite sign: if there was a swarm, you may find discarded wings nearby, and where they emerged matters more than that they exist. Wings on the windowsill →
The activity test
Photograph the whole run first, including where it meets the soil. Do this before touching anything — an inspector reads the run, and once it is broken the geometry is gone.
Then break a short section, an inch or so, from the middle. Not the whole tube.
Come back in three to five days.
Repaired means active. Termites rebuild a damaged road quickly, and a patched break is the clearest confirmation available without opening wood.
Not repaired is not an all-clear. They may have shifted to another route, or the colony may be working elsewhere in the same structure. It narrows the question; it does not close it.
An old, dry, crumbling tube that does not rebuild may be historical — evidence of a previous infestation, perhaps treated years ago. That is a real possibility and it still belongs on a report as previous activity.
What not to do
Do not knock the whole tube down. It destroys the evidence and tells you nothing you could not learn from breaking an inch.
Do not spray it. Over-the-counter product on a tube kills what is inside that inch and does nothing to a colony living in soil some distance away, while making a later inspection harder to read.
Do not seal or render over it. Covering the sign does not remove the road behind it.
Do not start digging at the foundation to trace it. Disturbing the soil around a structure ahead of a treatment can complicate the treatment.
What is probably nearby
A tube is the visible part of a set of conditions. While you are there, note anything that made the trip easy:
Wood in contact with soil anywhere on the structure.
Moisture — a downspout discharging at the foundation, a crawl space with standing water or no vapour barrier, a hose bib dripping.
Mulch piled against siding, which bridges the gap the builder left deliberately.
Firewood or timber stacked against the house, which is a food source with an introduction.
These are what an inspector calls conducive conditions, and they will be on the report whether or not there is an infestation. Fixing them is cheaper than the treatment and it is the part that keeps working afterwards.
What this means for you specifically
If you own and live in the home
Nothing has to be decided this afternoon. A colony that built that road has been at it for a while, and it will not become materially worse while you get a second quote.
Your action: photograph, break an inch, wait, and book an inspection meanwhile. Ask for inspection and treatment to be quoted as separate lines.
If you are selling
This is a wood-destroying insect finding, and it belongs on the report.
The standard Northern Virginia contract requires a report dated no more than 90 days before settlement and puts treatment and repair of the damage the report identifies on the seller, with written evidence before settlement. The repair is the half that surprises people.
Your action: get the inspection early in the contract period rather than against the settlement date. The contract clause →
If you are buying
A crawl space is one of the places a report most often records as inaccessible, and a tube on a pier is exactly what would have been seen there.
Your action: read the obstructions section first, and ask directly whether the crawl space was entered. Reading the report →
If you rent
The structure is the landlord's responsibility through the habitability duty under § 55.1-1220. Termites are a building matter, not a housekeeping one.
Your action: report in writing today with the photographs. Step by step →
If you are a landlord
Structural damage compounds, and a documented finding that sat untreated is a poor record to bring to a hearing.
Your action: inspect promptly, use a licensed operator, and address the conducive conditions in the same visit. What you owe →
Before you call: what costs what
An inspection and a treatment are two separate services with separate prices, and with termites there is reliably a third.
| Typical Virginia range | What it produces | |
|---|---|---|
| Wood-destroying insect inspection and report | $65–$200 | the NPMA-33 form |
| General pest inspection | often free where the company expects to quote treatment | a verbal or written assessment |
| Termite treatment | $500–$2,000; more where damage is extensive | a treatment record |
| Structural repair | quoted by a contractor, frequently the largest of the three | an invoice, not a pest control document |
What is usually free: a quote for treatment, once a company has seen the problem.
What is usually not: the inspection report used in a real estate transaction.
Ask which applies before you book. A single figure covering both inspection and treatment is not what a sales contract or a lender requires.
Common misunderstandings
"Mud tubes could be something else." Among the things found on Virginia houses, they could not. That is what makes this sign useful.
"I knocked it down, so it's handled." You removed a road. The colony is in the soil.
"No tubes, no termites." Tubes are one route. Where wood contacts soil directly, or where a slab crack gives cover, none is needed.
"It looks old, so it doesn't count." Previous activity is a category on the report and it belongs there.
"Sawdust near a tube means termites are making it." Eastern subterranean termites do not produce frass piles. Sawdust points elsewhere, usually to carpenter bees. What left the sawdust →
"Treatment stops the damage that's already done." Treatment addresses the colony. Existing damage is a repair question and a separate bill.
What to ask an inspector
- Is this activity current or previous, and what supports that?
- Which species, and what tells you so?
- What could you not access on this property, and what would it take to access it?
- What conducive conditions did you find, and what should change?
- What is the cost, quoted separately for inspection and for treatment?
- Does the damage need a contractor, and is that in your quote or not?
- Under what name is your Virginia pesticide business licence held?
What to have ready before you call
Property address and year built, foundation type and whether there is a crawl space, where the tubes are and on what, photographs of the full run, whether you broke a section and what happened, prior treatment history or an existing bond, and your settlement date if you are under contract.
Frequently asked questions
How quickly do they rebuild a broken tube? Often within a few days when the route is in use. Three to five days is a reasonable wait before drawing a conclusion.
Does one tube mean the house is riddled? No. It means there is a route in use, which is a reason to inspect rather than a measure of damage.
Can I treat this myself? Products for subterranean termites generally require licensed application, and a self-applied treatment will not satisfy a sales contract or support a tenant's deduction.
Do they only build on masonry? No — on piers, joists, sills, and sometimes free-standing from a slab. Masonry is simply where people look.
Is a bond worth having? It depends what it covers — retreatment only, or retreatment and repair — and what voids it. Ask for the exclusions in writing before comparing prices.
Verify before you pay anyone
VDACS publishes an updated list of licensed pesticide businesses weekly, with a public lookup confirming an active Pesticide Business License. Wood-destroying pest control is category 7b under 2VAC5-685-70 — not category 8, which several sites state and which is public health pest control.
Ask which name the licence is held under. The trading name and the licensed entity frequently differ, and a report is worth more when anyone can match the two. How to check →