Ask the Carpenter: Steps for dealing with carpenter ants

Ask the Expert Home Improvement
A winged carpenter ant.
A winged carpenter ant. ADOBE stock

Q. I’m looking for suggestions on how to access an ant nest. I noticed a trail of sawdust and wood shavings about 5 feet long on the outside of my garage wall. Do I take off the vinyl siding and then the wood shingles, or should I go in through the inside of the garage and cut out a section of drywall? What about drilling holes on the inside of the garage wall and fumigating the nest? Would the disruption cause the ants to scatter and make a new nest somewhere else inside the wall?

V.R., Beverly

A. Drywall removal and replacement is usually easier and less costly, but getting rid of the ants can be more challenging than that.

Ants are interesting creatures. Did you know that an ant can carry at least 50 times its body weight? I wish I could do that.

Do you know what type of ants you have? The most common types of ants you see inside a home are: carpenter, acrobat, pavement, and odorous house ants. If it’s carpenter ants, dealing with them can get a bit tricky. As a renovation contractor, I see carpenter ants in just about every home I work on, mostly around damp wood as a result of water intrusion or lack of proper maintenance.

Each ant species has unique characteristics that may affect how you approach this, but there are some very common methods you can deploy on your own. When dealing with ants, it’s best to take a moment to understand what they are and what they’re up to before trying to control or eradicate them.

Because of the sawdust, let’s assume that you have carpenter ants. “Carpenter ants are usually seen in homes in the spring. If you see carpenter ants indoors during winter, that means there is a nest inside your home,’’ according to a report by the University of Minnesota Extension and University of Wisconsin Extension: Carpenter ants live in colonies, which can range in size from hundreds to millions depending on the species. Carpenter ants — which eat meat, sweets, and dead insects — establish their colonies in galleries excavated from damp or damaged wood. Carpenter ants do not eat wood as termites do, but instead remove it and deposit the debris outside of their nests in small piles.

Carpenter ants are black or red and black and range from 3/16 to ½ inch in length, according to the report. Another indication of carpenter ant infestation will be the debris they produce from tunneling in the wood. Rough wood shavings mixed with parts of dead ants from the colony indicate carpenter ant-nesting activity.

I’ve seen nests in difficult-to-access spaces behind walls, cabinets, and appliances; behind window and door frames; and beneath floors and concrete slabs. That said, when dealing with an ant nest that is unknown or inaccessible, it’s best to hire a professional.

If you are going to try this on your own, many baits sold to homeowners come pre-packaged with the insecticide and food attractant in a plastic, child-resistant container. Follow all manufacturer recommendations on use and application. Don’t put it where children and pets can access it.

Place the bait in the ants’ path. If after a week or so, you don’t see fewer ants, try using a different bait. The best results require a sustained period of feeding. Common insecticides in ant baits include abamectin, fipronil, sulfluramid (may be listed as N-ethyl Perfluorooctanesulfonamide), disodium octaborate, orthoboric acid, and propoxur, according to the report. Professionals usually have a larger arsenal of bait, sprays, and dusts.

“Knowing what species of ant you have in your home helps to determine the nesting site, food preference, and the best method of management,’’ the university suggested. “In most cases, the most effective, permanent solution to eradicating the colony is to find and treat the nest; with the goal of killing the reproductive queens.’’

Good luck, and let me know how it goes.

Rob Robillard is a general contractor, carpenter, editor of, and principal of a carpentry and renovation business. Send your questions to or tweet them to @robertrobillard. Subscribe to our free real estate newsletter at