Getting rid of ants in your house requires a two-phase approach: eliminate the colony with bait, then seal the entry points so they don’t come back. Spraying visible ants with a kitchen cleaner feels satisfying, but it only kills the few you can see while the colony (sometimes numbering in the hundreds of thousands) keeps sending more. The most reliable method is letting worker ants carry slow-acting poison back to the nest, wiping out the queen and the entire colony from the inside.
Identify What You’re Dealing With
Not all house ants behave the same way, and knowing which species you have helps you pick the right bait and understand the urgency. The four most common indoor invaders are easy to tell apart with a close look.
- Argentine ants are about 1/8 inch long, dull brown, and travel in wide, visible trails. They prefer sweets year-round and form massive “supercolonies” with multiple queens linked across shallow underground nests. They’re the most common household ant in many regions.
- Odorous house ants are similar in size, dark brown to shiny black, and release a strong rotten-coconut smell when crushed. They nest in wall voids and around water pipes.
- Pavement ants are slightly larger at 3/16 inch, dark brown to black, and build visible sand mounds along foundations and sidewalks. They eat sweets, proteins, and grease.
- Carpenter ants are the big ones, ranging from 1/4 to 1/2 inch, black or red-and-black. They don’t eat wood, but they hollow it out to nest inside. Sawdust-like debris near baseboards, hollow-sounding wood, or faint rustling in your walls at night all point to carpenter ants, and they can cause real structural damage over time.
Use Bait, Not Spray
The instinct to grab a spray bottle of insecticide is counterproductive. Spray kills the ants it contacts but repels the rest, scattering them to establish new trails and sometimes new nests. Bait works because ants carry it back to the colony, where it spreads to the queen, larvae, and other workers. Once the queen dies, the colony collapses.
For sugar-feeding ants (Argentine, odorous house, and most other small household species), liquid bait is the most effective option. You can buy pre-filled bait stations or make your own. A simple homemade version: dissolve 1 cup of sugar in 1/2 cup of warm water, then stir in 1 tablespoon of borax. This creates roughly a 5% borax concentration, which is low enough that worker ants won’t detect the poison and avoid the bait (a behavior called “bait shyness”), but high enough to kill the colony over several days. Soak cotton balls in the solution and place them on small pieces of cardboard near ant trails and entry points.
A slightly different recipe uses boric acid instead of borax: 1/2 teaspoon of boric acid, 8 teaspoons of sugar, and 1 cup of warm water. Both work through the same mechanism. The key is keeping the concentration low so foragers keep feeding and sharing.
For ants that prefer protein or grease (pavement ants often do), mix borax or boric acid powder with maple syrup or corn syrup, spread it on a flat piece of cardboard, and place it in high-traffic areas. If you’re not sure what your ants prefer, set out both a sweet bait and a protein bait and see which one draws a crowd.
Resist the urge to kill the ants you see feeding at the bait station. Those workers are your delivery system. It typically takes a few days to two weeks for the bait to circulate through the colony and reach the queen. You may see ant activity increase initially as more workers discover the bait. That’s a good sign.
DIY Repellents and Contact Killers
Several household products can kill or repel ants on contact, which is useful for managing visible trails while your bait does its deeper work. None of these will eliminate a colony on their own, but they help with immediate cleanup and trail disruption.
Diatomaceous earth (the food-grade kind) kills ants by absorbing the oils in their exoskeletons, drying them out. Sprinkle a thin layer along baseboards, behind appliances, or anywhere you see trails. It works well in dry areas but loses effectiveness when wet. White vinegar mixed 1-to-1 with water and wiped across countertops and floors destroys the chemical scent trails ants follow, forcing them to re-scout. Peppermint essential oil (10 to 20 drops in 2 cups of water) works similarly as a trail disruptor and has the side benefit of smelling pleasant.
For outdoor nests you can locate, pouring boiling water directly into ant holes kills many ants immediately. This won’t reach deep colonies, but it reduces the population pushing toward your house.
Seal Every Entry Point
Killing the current colony solves today’s problem. Sealing your home prevents the next one. Ants exploit surprisingly small gaps, and a few hours with a caulk gun can make a lasting difference. Focus on these five areas first, in order of how commonly ants use them:
- Foundation sill plate: the joint where the wood framing meets the concrete foundation. Run a bead of 100% silicone caulk along the entire seam.
- Utility penetrations: every hole where water pipes, electrical conduit, cable lines, or HVAC lines pass through an exterior wall. For gaps under 1/4 inch, silicone caulk is enough. For gaps between 1/4 inch and 1 inch, fill with expanding pest-block foam and cap with silicone once cured. For gaps over 1 inch, pack copper mesh into the opening first, then foam, then silicone. Carpenter ants can chew through cured foam alone but won’t chew through copper mesh.
- Door thresholds: install an automatic door sweep or aluminum threshold with a vinyl seal insert. Caulk the exterior door frame where it meets the siding with a 1/4-inch bead of silicone.
- Window frames: especially on north- and west-facing walls where moisture collects. Fill cracks in window trim with paintable polyurethane caulk. Replace torn screens (a fiberglass screen kit runs about $20).
- Roof soffits and any wood-to-ground contact: landscaping timbers, mulch beds pushed against siding, and firewood stacked against the house all create direct highways for ants.
One important note on caulk types: acrylic latex caulk and siliconized acrylic blends are poor choices for ant exclusion. Ants chew right through these softer formulations, especially in damp areas. Stick with 100% silicone for most jobs or polyurethane caulk for joints that see significant movement, like where siding meets trim.
Inside the house, run a continuous bead of paintable caulk along the base of every baseboard in kitchens, bathrooms, and utility rooms. This disrupts interior trails permanently and takes away the small crevices ants use to move unseen between rooms.
Cut Off Food and Water Sources
Ants enter homes for two reasons: food and moisture. Removing both makes your house a less attractive target even if a few scouts find their way in. Wipe down counters and stovetops after every meal. Sweep floors in the kitchen daily, paying attention to crumbs under the stove and refrigerator. Store sugar, honey, cereal, and pet food in airtight containers. Rinse recycling before it goes in the bin, since a sticky soda can is a beacon for sugar-feeding ants.
Fix leaky faucets and pipes promptly. Ants, especially odorous house ants, are drawn to consistent moisture around pipes, water heaters, and under sinks. Reducing indoor humidity with proper ventilation in bathrooms and crawl spaces removes another reason for ants to nest inside your walls.
When Carpenter Ants Need Professional Help
Most small ant species are a nuisance, not a structural threat. Carpenter ants are the exception. Because they carve smooth, clean tunnels through wood to build their nests, an established colony can weaken support beams, floor joists, and wall studs. In advanced infestations, floors sag, walls warp, and minor collapses can occur in damp areas.
The trouble is that carpenter ants often nest in hidden spaces, so the true extent of damage is rarely visible until the wall is opened up. If you’re seeing large black or red-and-black ants indoors regularly, finding small piles of wood shavings near baseboards or door frames, hearing faint rustling inside walls at night, or spotting winged ants emerging indoors, a professional inspection is worth the cost. A licensed pest control technician can locate all nests (there are often satellite colonies in addition to the main one), confirm the species, and apply targeted treatments in wall voids and structural wood that DIY methods can’t reach.