Signs Carpenter Ants Are Nesting In Your Walls

Carpenter ants are large, wood-excavating insects that can cause significant structural damage over time if left unchecked. Unlike termites, they do not eat wood but tunnel through it to build galleries and nests. When carpenter ants choose to nest inside wall voids, they often remain hidden for months or years before signs become obvious. This article explains the most reliable indicators that carpenter ants are nesting in your walls, how to confirm an infestation, what immediate steps you can take, and how to prevent a recurrence.

Why carpenter ants in walls are a serious problem

Carpenter ants remove wood to create smooth, clean galleries where the queen lays eggs and the colony grows. Over time this excavation weakens structural elements like studs, joists, and subflooring. Walls conceal the damage, making early detection difficult. In addition to structural risk, colonies produce frass (sawdust-like debris) and create exit holes that allow moisture and other pests to enter. A small, active colony can expand rapidly over several months to years, so early identification matters.

Common signs of nesting inside walls

Below is a prioritized list of the most diagnostic signs you can observe without removing drywall or doing destructive testing.

• Visible ant activity near walls, baseboards, outlets, or windowsills.
• Presence of winged ants (swarmers) inside the house, especially during spring and summer.
• Small piles of wood debris or frass near baseboards, under eaves, or in cupboards.
• Rustling, tapping, or scraping noises coming from wall voids at night.
• Small, clean, oval exit holes in wood trim, siding, or external walls.
• Discolored, softened, or damaged wood that sounds hollow when tapped.
• Trails of worker ants moving between nest entry points and food sources.
• Increased ant activity at dusk and after dark near interior walls.
• Finding live or dead worker ants that are larger than common house ants (often 1/4 to 1/2 inch or larger).
• Evidence of multiple satellite nests or foraging routes between tree limbs and wall entry points.

Each sign by itself might not guarantee an active wall nest, but the combination of several items on this list strongly indicates a colony is present inside structural voids.

What the evidence really means

Not all ants you see indoors are nesting in the walls. Distinguish between foraging worker ants and colony members that remain inside walls:

• Foraging workers: These ants are hunting for food and typically follow scent trails. They may enter the house from outside and disappear back into cracksneardoors and windows. Occasional workers do not necessarily mean a nest inside the wall.
• Nesting activity: Persistent ant trails that originate from a consistent point on a wall, piles of frass beneath a specific location, audible activity behind drywall, or the presence of winged swarms indoors all point to a nesting site in a wall void.

Winged swarms serve a special diagnostic role. If you discover large numbers of winged males and females indoors, especially near windows or light sources, it is likely the nest is inside your home.

How to inspect your home for a wall nest

A careful inspection can often reveal where ants are entering and where a colony might be located. Follow these practical steps.

• Conduct a daytime and after-dark inspection. Carpenter ants are more active at night. Use a flashlight to trace trails and locate entry points.
• Follow ant trails to their source. Observe where workers disappear into walls, trim, baseboards, or flooring seams.
• Look for frass and exit holes. Check corners, behind appliances, inside cabinets, and in attics and crawlspaces for small sawdust-like piles.
• Tap suspect wood. Use a screwdriver handle or small hammer to gently tap wood. Hollow-sounding wood or a raspy feedback may indicate galleries behind the surface.
• Listen for noise. At night, hold a stethoscope or a rolled paper cone against walls to detect rustling or chewing sounds.
• Check exterior connections. Inspect where tree limbs touch the house, where siding meets foundations, and around eaves for ant activity that could access wall voids.
• Examine moisture sources. Carpenter ants prefer damp or decayed wood. Inspect plumbing, roof leaks, and condensation-prone areas.
• Use monitoring tools. Place sticky traps along suspected trail lines or near suspected entry points to capture ants for species identification.

Make notes and photographs of what you find. Documented evidence helps a professional pest control technician target treatment more quickly and can be useful if structural repairs are needed.

How to identify carpenter ants

Correct identification matters because treatment differs from that used for other ants or termites. Key identifying features include:

• Large size: workers are typically 6 to 12 millimeters long depending on species.
• Rounded thorax profile when viewed from the side.
• Single node (petiole) between thorax and abdomen.
• Smooth, evenly segmented antennae without a distinct “elbow.”
• Color ranges from black to red and black or brownish.

If you are unsure, collect a few specimens in a sealed container and show them to a local extension office or pest control professional for confirmation.

Immediate steps to take if you suspect a wall nest

If your inspection suggests an active carpenter ant colony inside a wall, act promptly. Early intervention limits damage.

1. Reduce attraction. Keep food sealed, remove pet food at night, and store sweet or greasy foods in sealed containers.
2. Eliminate moisture. Repair leaks, improve ventilation in bathrooms and attics, and ensure gutters and downspouts move water away from the foundation.
3. Block easy access. Seal cracks in foundation, repair damaged siding, and trim tree limbs or shrubs that contact the house.
4. Set bait stations. Use slow-acting ant baits specifically formulated for carpenter ants so workers carry the bait back to the colony. Place baits along trails and near entry points.
5. Do not waste time with perimeter sprays alone. Surface sprays can kill foraging workers but often fail to eliminate the hidden colony inside wall voids and can scatter ants to new areas.
6. Contact a licensed pest control professional if you locate frass piles, winged swarmers indoors, or if baits fail after a few weeks.

Follow-up is critical. Carpenter ant colonies can have satellite nests; ongoing monitoring and multiple treatments may be needed.

When to call a professional

Call a licensed pest control professional if any of the following apply:

• You find active frass or a large number of ants exiting a consistent location.
• You hear activity behind walls, especially near structural timber.
• Winged swarmers are present inside the home.
• You discover visibly damaged, hollowed, or fractured structural wood.
• DIY baiting and exclusion steps fail after two to four weeks.

Professionals can perform targeted inspections with borescopes or thermal imaging, identify the scope of the infestation, and apply treatments such as dusts in voids, liquid barrier treatments, or targeted baiting that reach the colony core.

Long-term prevention and repair

Stopping reinfestation requires addressing the root causes and repairing damaged wood.

• Repair water leaks, roof flashing, and damaged siding that allow moisture or rot to develop.
• Replace or reinforce wood that has been significantly excavated by ants.
• Maintain a 12- to 18-inch clearance between soil and wood siding; avoid storing firewood against the house.
• Seal entry points with caulk and install door sweeps. Use 1/4-inch mesh on vents to prevent ant ingress.
• Maintain vegetation so branches and shrubs do not touch the structure.
• Schedule periodic inspections if you live in an area prone to carpenter ants.

Professional structural repair may be necessary when load-bearing members are weakened. A licensed contractor or structural engineer can assess the safety and recommend repairs.

Practical takeaways and checklist

• If you see persistent ant trails that lead to a point on a wall, suspect an internal nest.
• Small piles of coarse, sawdust-like frass are a hallmark sign of carpenter ant excavation.
• Winged ants inside the house during swarming season are a strong indicator the nest is in the structure.
• Listen at night for rustling behind drywall or hollow-sounding wood when tapped.
• Use baits designed for carpenter ants and focus placement along trails and entry points.
• Repair moisture problems and seal access points to reduce the chance of reestablishment.
• Call a professional if you locate frass, structural damage, or if DIY measures do not control the population within a few weeks.

Carpenter ant infestations can be stopped and repaired when detected early. A careful inspection, combined with targeted baiting, moisture control, and, when necessary, professional intervention, will protect the structural integrity of your home and prevent future infestations. Keep a written record of sightings and treatments so you can track progress and provide useful information to any pest control service you hire.