How to Get Rid of Carpenter Ants in Walls

Hearing a faint rustling inside a wall or spotting large black ants trailing across the kitchen at night is unsettling, and for good reason: these insects tunnel through wood and can weaken your home over time. Learning how to get rid of carpenter ants in walls means finding the nest, treating it directly, and eliminating the moisture and entry points that attracted them. Unlike termites, carpenter ants do not eat wood, but they carve smooth galleries in it to nest. This guide covers how to identify them, the treatments that actually work, and when to bring in a pro.

Identify the Problem First

Carpenter ants are large, usually 1/4 to 1/2 inch long, and most often black, though some are red and black. Signs they are nesting in your walls include:

• Piles of fine sawdust-like shavings, called frass, near baseboards or window frames
• A faint crackling or rustling sound inside walls, especially at night
• Large winged ants (swarmers) appearing indoors in spring
• Trails of ants active mostly after dark
• Hollow-sounding or soft wood around windows, doors, or damp areas

Because carpenter ants prefer moist, softened wood, their presence often points to a hidden leak or condensation problem you will need to fix along with killing the colony.

Find the Nest

Killing the ants you see does little; you have to reach the nest. Carpenter ants often build a main colony outdoors in a stump or woodpile, with satellite nests inside the home’s damp wood. To locate the indoor nest, watch where ants travel, especially at night with a flashlight. Follow the trail back toward the wall. Areas near leaky plumbing, roof leaks, bathrooms, kitchens, and window frames are prime spots. Tapping walls and listening for a hollow sound, or watching where frass accumulates, helps pinpoint the gallery.

The Most Effective Treatment: Bait

Slow-acting bait is the gold standard because worker ants carry it back to the nest and feed it to the colony, including the queen. This wipes out the whole nest rather than just the foragers. Place carpenter ant bait, either gel or granular, along ant trails and near entry points, not directly on the nest, so the ants keep foraging and sharing it. Products with borate or indoxacarb work well. Be patient; baiting can take one to two weeks to collapse a colony. Do not spray insecticide on the trails at the same time, because killing foragers too fast prevents them from spreading the bait.

Treating the Nest Directly With Dust

When you find the nest in a wall void, an insecticidal dust is highly effective. Products containing boric acid or a pyrethroid dust can be puffed into the wall through small holes drilled near the gallery, or through existing cracks and electrical outlet openings (with power off). The dust coats the ants and spreads through the nest. A bulb duster costs about $10 and lets you apply it precisely. This approach reaches ants deep in the void that surface baits might miss, and it is often combined with baiting for a thorough knockout.

Step-by-Step Treatment Plan

1. Confirm and locate. Verify they are carpenter ants and trace their trails to the nest area.
2. Fix moisture. Repair any leaks and dry out damp wood, since moisture is what drew them in.
3. Set bait. Place slow-acting bait along trails and near entry points, and leave it undisturbed.
4. Dust the void. If you find the wall nest, puff insecticidal dust into the gallery through small holes or outlets.
5. Treat the exterior. Find and treat any outdoor parent colony in nearby stumps, woodpiles, or trees.
6. Monitor. Watch activity for two to three weeks and reapply bait as needed until the ants disappear.

Tools and Products You Will Need

• Carpenter ant bait (gel or granular): $8 to $15
• Insecticidal dust with a bulb duster: $15 to $25 total
• Flashlight for nighttime tracking
• Caulk and sealant for entry points: $6 to $10
• A moisture meter to find damp wood, optional: $20 to $40

Prevent Them From Coming Back

Eliminating the colony is only half the battle; prevention keeps them out for good. Fix the moisture problems that attract them, whether a plumbing leak, a leaky roof, poor grading, or bathroom condensation. Trim tree branches and shrubs away from the house so ants cannot bridge onto the structure. Store firewood off the ground and away from the foundation. Seal cracks, gaps around utility penetrations, and spaces around windows and doors with caulk. Replace any water-damaged or rotted wood, since softened wood is exactly what carpenter ants seek out.

Common Mistakes to Avoid

The most common error is spraying visible ants with a contact killer and assuming the problem is solved, when the nest remains untouched and often just relocates. Another mistake is ignoring the underlying moisture, guaranteeing a return infestation. People also place bait directly on the nest, which can repel the ants, or use bait and spray together so foragers die before sharing the bait. Finally, misidentifying carpenter ants as termites, or vice versa, leads to the wrong treatment; termites eat wood and require entirely different control.

When to Call a Pro

DIY treatment handles many carpenter ant problems, but call a licensed pest control professional if you cannot locate the nest, if the infestation is large or recurring, if the ants have damaged structural wood, or if satellite nests are spread through multiple walls. A pro has the tools to inspect wall voids, apply targeted treatments, and identify the parent colony outdoors. If you find soft, structurally compromised framing, also consult a contractor about repairs. Professional carpenter ant treatment typically runs $250 to $500, and it is worthwhile insurance against ongoing structural damage.

Carpenter Ants vs. Termites: Know the Difference

Correctly identifying the pest determines the right treatment, and carpenter ants are frequently confused with termites. Both can swarm indoors and damage wood, but they look and behave differently. Carpenter ants have a pinched, narrow waist, bent (elbowed) antennae, and if winged, two sets of wings of different lengths. Termites have a straight, thick waist, straight antennae, and two pairs of equal-length wings. Carpenter ants push frass, resembling coarse sawdust mixed with insect parts, out of their galleries, while termites leave mud tubes and their galleries are packed with soil and look rough rather than smooth.

The distinction matters because termites eat the wood itself and cause damage far faster, requiring specialized treatment and usually professional intervention. Carpenter ants only excavate wood to nest, working more slowly. If you find mud tubes on your foundation or hollowed wood packed with dirt, suspect termites and call a pest professional right away. Smooth, clean galleries with sawdust-like frass nearby point to carpenter ants, which the bait-and-dust approach in this guide handles well.

Getting rid of carpenter ants in walls takes a two-pronged approach: kill the colony with bait and dust, and remove the moisture and entry points that invited them in. Be patient with baiting, treat any outdoor parent nest, and fix the leaks. If the nest hides or the damage is extensive, a licensed pro is the right call.