Carpenter ants in Michigan follow moisture-damaged wood. They do not eat the wood — they excavate galleries inside it, leaving behind a smooth, sawdust-like material called frass. Fix the water source and remove the soft wood, and you eliminate the attraction. The prevention guide below covers the 9-step moisture-control checklist and explains why a single retail spray almost never works: it kills the workers you can see, not the queen and brood inside the wall.
The Moisture Connection
Carpenter ants in Michigan target wood that has been softened by moisture. That means roof leaks at flashing, plumbing drips inside walls, ice-dam damage at the eaves, gutter overflow against siding, crawlspace humidity, decks with no ground clearance, firewood stacked on the foundation, and tree branches touching the roof. Every BTR carpenter ant call traces back to one of those sources. If the moisture is not addressed, treatment is a temporary fix and the colony returns.
Most Michigan homes have a parent colony outdoors in a moisture-rotted stump, log, or tree, and one or more satellite colonies indoors in wall voids, attic insulation, or moisture-damaged framing. Treatment that only kills the satellite leaves the parent colony to send new workers back. That is why spraying at the trail rarely works long-term.
The 9-Step Carpenter Ant Prevention Checklist
- Fix all roof and plumbing leaks. Even small chronic drips soften framing over time and become carpenter ant habitat.
- Clean gutters and extend downspouts. Overflowing gutters spill water against the foundation and the siding. Extend downspouts a minimum of 5 feet from the foundation.
- Grade soil away from the foundation. A minimum 6-inch drop over the first 10 feet keeps water moving away from the house instead of pooling against it.
- Fix crawlspace and basement humidity. Vapor barrier on the floor of the crawlspace, dehumidifier in damp basements. Carpenter ants thrive in humidity above 70 percent.
- Trim tree branches touching the roof. Branches form bridges from the parent colony in a yard tree directly to the satellite colony in your attic.
- Store firewood away from the house and off the ground. At least 20 feet away, stacked on a rack at least 6 inches off the soil. Firewood stacked against the house is a carpenter ant hotel.
- Replace any moisture-damaged wood. Window sills, door frames, fascia boards, deck posts, sill plates — any wood you can press a screwdriver into is colony habitat. Replace it.
- Seal exterior gaps. Same gap survey as rodent exclusion: caulk every opening larger than 1/4 inch with exterior-grade sealant. Carpenter ants follow wiring, plumbing, and HVAC penetrations into wall voids.
- Schedule professional inspection in fall. Fall (September through November) is when carpenter ant colonies consolidate — satellites retract toward the parent colony. This is the best inspection window because the colony is concentrated and locatable.
Why Ants Come Back After You Spray
A retail spray hits visible foragers on the kitchen counter or on a baseboard. Those foragers are 5 to 10 percent of the colony. The other 90 to 95 percent — the queen, the brood, the developing workers — are inside the wall or under the deck where the spray cannot reach. Within days, new foragers replace the dead ones and the trail comes back. The math does not work in the homeowner's favor.
BTR uses an exterior product with a transfer effect: foragers contact the product, carry it back into the colony on their bodies, and contaminate the food source the rest of the colony depends on. The queen feeds on contaminated food and dies. The brood dies with her. The colony collapses. That is why BTR's carpenter ant treatment carries a 90-day warranty — the product is designed for colony-level kill, not surface kill. See the full carpenter ant service page for the process detail.
Signs You Already Have a Carpenter Ant Colony
- Large black ants indoors year-round. Carpenter ants are 1/4 to 1/2 inch long, black, with a single segmented "waist" between thorax and abdomen.
- Winged ants (swarmers) indoors in spring. Indoor swarmers indicate an established interior colony, not a new one. The parent colony is mature enough to reproduce.
- Sawdust-like frass on baseboards, windowsills, or under decks. Smooth and uniform — this is the excavated wood the ants have pushed out of their galleries.
- A faint rustling sound inside a wall on a quiet evening. Large colonies are audible.
- Trails on countertops, around sinks, and behind dishwashers. Indoor foragers follow water sources.
See the carpenter ant identification page for photos comparing carpenter ants to termites (both excavate wood; identification matters because treatment is different).
When to Call BTR
Call BTR if you see large black ants indoors year-round, find frass anywhere, see indoor winged ants in spring, or hear rustling in a wall. Carpenter ant treatment starts at $255 and carries a 90-day warranty. The fall inspection window (September through November) catches colonies in their consolidated state and is the most efficient time to treat. See the spring pest guide for what to watch for once carpenter ants emerge in March.
Frequently Asked Questions
Do carpenter ants eat wood?
No. Carpenter ants do not eat wood. They excavate galleries inside moisture-damaged wood to create nesting space, pushing the chewed-out material (called frass) out of the gallery. The frass looks like a small pile of fine sawdust mixed with bits of insect parts. They eat sugars, proteins, and other insects — not wood.
What is the difference between carpenter ants and termites?
Carpenter ants have a pinched waist and elbowed antennae; termites have a straight waist and straight antennae. Carpenter ants push frass out of their galleries; termites eat the wood and build mud tubes. Both damage wood but treatment is completely different, so identification matters.
Why do carpenter ants keep coming back?
Retail spray kills visible foragers (5 to 10 percent of the colony) but not the queen and brood inside the wall (90 to 95 percent). Within days, new foragers replace the dead ones. Permanent control requires professional treatment with a transfer-effect product that contaminates the colony food source and kills the queen.
What attracts carpenter ants to a house?
Moisture-damaged wood is the #1 attraction. Roof leaks, plumbing drips, ice-dam damage at eaves, gutter overflow against siding, crawlspace humidity, decks without ground clearance, firewood stacked on the foundation, and tree branches touching the roof all create either habitat or travel routes.
What do indoor winged carpenter ants mean?
Indoor winged carpenter ants (swarmers) in spring mean an established interior colony. Carpenter ants only produce reproductives once a colony is mature, which takes 3 to 6 years. Seeing swarmers indoors means the colony has been in the structure for years and is now reproducing.
When is the best time to treat carpenter ants?
Fall (September through November) is the best treatment window because carpenter ant colonies consolidate in fall, pulling workers and queens from satellite colonies back into the parent colony. This concentrates the colony and makes location and treatment far more effective. Spring works too but the colony is more dispersed.
Can I prevent carpenter ants without using chemicals?
Yes — the moisture-control side of the prevention checklist is entirely chemical-free. Fix leaks, fix gutters, fix humidity, replace softened wood, trim branches, move firewood, seal gaps. Eliminating moisture-damaged wood removes the habitat carpenter ants need. Treatment is for active colonies; prevention is largely a maintenance discipline.
Suspect a Carpenter Ant Colony?
Free inspection. Transfer-effect treatment kills the queen. 90-day warranty.
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