How to get rid of carpenter ants
Carpenter ants don't eat wood — they tunnel through it to nest, almost always in wood that's already wet or damaged. The fix has two halves: kill the colony with bait, then find and fix the moisture problem that brought them in. Skip the moisture step and they come back.
Tools
- ✓For trace work along trails and inspection of suspected nest sites.
- ✓For tapping suspect wood — hollow sound or soft probe indicates damage.
- ✓Locates the wet wood the ants are nesting in.
Materials
- +Granular bait specifically formulated for carpenter ants. Place along trails — workers carry back to nest.
- +Liquid bait alternative. Works well for some colonies that won't take granular.
- +Non-repellent perimeter treatment. Ants don't detect it and carry it back to the nest. Check your state's rules — restricted in some areas.
- +For sealing exterior entry points after the colony is dead.
Steps
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1
Confirm carpenter ants vs other big black ants
Carpenter ants are 1/2 to 5/8 inch (very large), all black or black-and-red. Single node between thorax and abdomen. Smoothly rounded thorax. If you see piles of sawdust-like material (frass) under a suspect spot, that's a strong tell.
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2
Trace activity to the nest
Observe foraging trails at dusk (peak activity). Trails often lead outside to the parent nest — a dead tree, woodpile, stump, or wet structural wood. Indoor 'satellite' nests usually trace back to an exterior parent. Photograph the trails.
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3
Find and fix the moisture source
Check around windows for leaking flashing, roof leaks above ceiling damage, plumbing leaks under sinks/bathrooms, condensation around pipes. Use the moisture meter on any wood the ants are around. Fix the leak before doing anything else.
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4
Place granular bait along trails
Sprinkle Advance bait at trail intersections and along the path workers walk. Don't disturb the trail — let them find the bait naturally. Workers carry it back to feed the colony.
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5
Treat the exterior perimeter (where legal)
Apply Termidor SC in a 3-foot band around the foundation. Ants pick up the non-repellent active ingredient and transfer it through colony grooming. Slow-acting by design — kills the whole colony over 2–4 weeks.
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6
Replace damaged wood and seal entry
Once trails go quiet (typically 4–6 weeks), replace any structurally damaged wood. Caulk gaps where pipes/wires enter the house. Trim tree branches that touch the roofline.
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7
Monitor for the next 6–12 months
If you didn't fully eliminate moisture issues or missed a satellite nest, activity returns. Place monitoring stations in suspect areas. Recurrence after 6 months usually means another untreated colony — get a pro inspection.