Pest Library
Carpenter Ants
Large black ants that excavate damp or damaged wood.
Overview
Carpenter ants are the large ants — often 1/4 to 5/8 inch — that homeowners notice one at a time rather than in a neat trail. They do not eat wood. They tunnel through it to build smooth, clean galleries for their nest, preferring wood that has been softened by moisture.
A property can have a parent colony in a tree stump or woodpile outside and one or more satellite nests inside a wall, window header or porch column. Finding the ants indoors during cold months is the strongest signal that a nest is inside the structure.
Why they're common in the Hudson Valley
- Wooded lots, standing dead trees, stumps and stacked firewood provide abundant parent-colony habitat within foraging distance of homes.
- Freeze-thaw cycles, ice dams and wind-driven rain create the chronically damp wood carpenter ants prefer — especially around roof edges, gutters, decks and bay windows.
- Many older Hudson Valley houses have original wood trim, porches and additions where past leaks left moisture-damaged framing.
Signs of activity
- Large black or black-and-red ants indoors, especially at night
- Coarse sawdust-like shavings (frass) with insect parts below trim, sills or ceilings
- Faint rustling or crinkling sounds inside a wall or ceiling on a quiet night
- Winged ants emerging indoors in spring
- Wood that sounds hollow or feels soft near windows, decks or roof lines
Where you'll find them
- Window and door headers, especially where flashing or caulk has failed
- Bathroom and kitchen walls near plumbing
- Attic rafters near roof leaks and around chimney flashing
- Porch columns, deck ledgers, sill plates and crawlspace framing
- Outdoors in stumps, dead limbs, landscape timbers and firewood
Why it matters
- Carpenter ant galleries weaken structural and trim wood over time, and the damage often follows an unrepaired water problem.
- Because they nest in voids, the visible ants rarely indicate the true nest location — surface sprays can scatter satellite colonies rather than eliminate them.
- Finding the moisture source is usually as important as treating the ants.
Prevention
- Keep firewood off the ground and away from the house
- Remove stumps and dead limbs near the structure when practical
- Repair roof, gutter, flashing and plumbing leaks promptly
- Trim branches that touch the roof or siding
- Replace water-damaged trim, sills and deck boards rather than painting over them
- Improve crawlspace and basement ventilation to lower wood moisture
When to get an inspection
- You see large ants indoors during winter or early spring
- You find frass piles or hollow-sounding wood
- You hear activity inside walls or ceilings
- Ants keep returning to the same room after treatment
Seeing large black ants indoors?
If the activity keeps coming back, an on-site inspection is the reliable next step.
Related pests
Keep reading
Carpenter Ants vs. Termites: How to Tell the Difference
Both damage wood, but they leave very different evidence — and the response to each is different too.
What Attracts Carpenter Ants to a Home?
Carpenter ants rarely pick a house at random. Nearly every case traces back to water, wood and proximity.