Why do I hear rustling in my walls at night?

What that rustling in your walls actually is

That soft, papery crackle behind your drywall is almost always carpenter ants excavating tunnels. They chew galleries into wood to build their nest, and the sound carries through the hollow wall cavity like a speaker.

It's loudest at night, usually from dusk to a few hours after dark. That's when the colony is most active and the rest of the house is quiet.

Here's the part people get wrong: carpenter ants don't eat the wood. They chew it out and dump it. So the damage is slower than termites, but a mature colony left alone for years can still hollow out important framing.

The good news is this is fixable. The catch is that finding and killing the actual nest usually takes a licensed pro, which is why we rate this problem pro-friendly rather than DIY.

Why carpenter ants picked your wall

Carpenter ants don't dig into just any wood. They go for wood that's already softened by water, which is why nearly every wall infestation ties back to a moisture problem.

Think slow roof leaks, sweating supply lines behind a kitchen or bath, a leaky window flashing, or a rotted door sill. The ants follow the damp, then set up shop.

Sometimes the wall nest is a satellite. The parent colony lives outside in a stump, a woodpile, or a dead branch, and workers travel a trail inside. If you treat only the wall, the source keeps refilling it.

Timing matters too. A colony that moved in during fall can go quiet all winter, then suddenly get loud in early spring. People swear it's brand new when really it's been there for months.

And occasionally the culprit isn't ants at all. Mice in the insulation make a similar rustle. The difference is character: ants are a fine steady crackle, rodents are heavier bursts with gnawing and the odd thump.

Step by step: confirm it before you spend money

Start at night, because that's when they're loudest. Walk the wall and find the spot where the rustling peaks.

Then get down low and hunt for frass. Carpenter ants push their excavated wood out through small slit-like openings, leaving coarse sawdust with tiny insect parts mixed in. It collects below baseboards, window frames, and trim gaps.

Check moisture next. Look for water stains, bubbled paint, or wood that feels soft when you press it. in most cases, the moisture and the nest are close together.

Now go outside at dusk with a flashlight. Trace any ant trails along the foundation, up utility lines, or across tree branches touching your roof. Following the trail can reveal an outdoor parent nest.

Clean up the perimeter: pull mulch and firewood back from the foundation and trim branches off the house. You're removing highways and food sources.

Then book a licensed inspection. Tell the tech specifically that you want the parent nest located, not just a spray where you hear the noise.

• Frass below wall gaps: strong sign of an active nest
• Soft or stained wood nearby: the moisture that drew them in
• An outdoor trail: points to a satellite-parent setup
• Winged ants indoors in spring: a mature breeding colony

What this costs in 2026

Professional carpenter ant treatment for a typical single-family home runs $150–$600. That usually covers an inspection, targeted treatment of the nest and trails, and a perimeter application.

Colony size, access, and how many nests exist all move the number. A single easy-to-reach wall nest sits at the low end; multiple satellites or a hard-to-access void pushes it up.

That can help around the edges, but it rarely ends a wall infestation on its own.

The bigger cost is often the repair, not the ants. If a leak softened structural wood, you're looking at carpentry and moisture work that can run well past $1,000. Ants are usually the cheap part.

DIY versus calling a pro

Here's the honest boundary. You can absolutely do the detective work: find the loud spot, spot frass, trace trails, and fix easy moisture issues. That's real, useful progress.

What trips up homeowners is treatment. The foragers you see are rarely near the nest, and spraying them does nothing to the queen. Worse, repellent sprays can cause a stressed colony to split into new satellite nests, which spreads the problem.

A licensed pro brings two things you probably don't have: the ability to locate the actual nest, and non-repellent products plus baits that workers carry back to the queen. That's what collapses the colony.

If the noise is faint, you've found the trail, and it leads to a stump you can treat outside, a careful DIY bait approach might work. For anything inside a wall with frass, hire it out.

Can this wait?

For a week or two while you get an inspection scheduled? Sure. For a season or a year? No.

Carpenter ant colonies grow, and a comfortable wall nest near moisture is prime real estate. Given time, it throws off satellite nests into other walls, and the excavation spreads.

The moisture problem that invited them is also getting worse in the background. Rot and mold don't pause while you decide.

The clearest warning sign is winged swarmers appearing indoors in spring. That means the colony is mature enough to reproduce, and you've likely had it longer than you think. Don't sit on that one.

Why the noise changes with the seasons

Carpenter ants track temperature. In winter they slow way down and go quiet, which is why a lot of people think their problem disappeared on its own.

The first warm week of spring wakes them up. March through May is when overwintering colonies get loud again and when swarmers show up looking to start new colonies.

Summer is peak activity. If the rustling is constant and easy to hear every night, you're probably in the height of the season with a decent-sized colony.

Late fall brings a second bump as ants pack into warm wall cavities ahead of winter. If your problem started in October or November, they were setting up for the cold.

How we approached this guidance

This page reflects standard field diagnosis for carpenter ant activity in residential walls: locating the nest by sound and frass, confirming the moisture source, and separating satellite nests from parent colonies.

Cost ranges are 2026 US estimates for typical single-family homes and will vary by region, colony size, and access. Always get a written quote after an in-person inspection.

The DIY-versus-pro line here is deliberately conservative because repellent sprays commonly make carpenter ant problems worse by splitting colonies. When in doubt, get a licensed inspection before you treat anything.