What Attracts Carpenter Ants to Your House?

The most useful correction to make about carpenter ants is that they are not eating your house. Unlike termites, carpenter ants don't digest cellulose; they chew wood only to create smooth galleries for nesting, discarding the shavings as frass. Penn State Extension and University of Minnesota Extension both describe a strong preference for wood that's already been softened by moisture, because it's dramatically easier to excavate than dry, sound lumber.

That preference explains the colony structure that actually brings ants indoors. The main, egg-laying colony is usually outdoors — in a rotting stump, a woodpile, or a dead tree — where a moisture-rich, softened-wood environment is naturally available. From there, the colony can establish satellite nests, and those are the ones that move into a structure, always into wood with a moisture problem: around a roof leak, failed flashing, a clogged or poorly pitched gutter, or long-term condensation in an attic or crawlspace. Ohio State University Extension makes the same connection between indoor carpenter ant activity and an underlying moisture source. In practice, that makes carpenter ants an indicator species: finding them inside usually means there's a leak or condensation problem worth finding, which is a different and more useful question than "food, water, and nesting spots" suggests. Structural damage assessment is a separate topic covered at /faq-pest-damage-and-risks.