Keeping ants out of your house comes down to three things: eliminating what attracts them, sealing the gaps they use to get inside, and dealing with the colony itself rather than just the visible workers. Most ant problems start outdoors and move in when ants find reliable food or moisture sources, so a lasting fix addresses both sides of your walls.
Know Which Ants You’re Dealing With
Not all ants respond to the same strategies. The species in your kitchen determines what bait to use, where to look for nests, and how urgently you need to act.
Odorous house ants are the most common indoor invaders. They’re small, dark brown, and release a rotten coconut smell when crushed. They nest in soil under stones, mulch, or boards outside, but will move into wall voids and under floors when they find moisture indoors. They’re after anything sweet.
Pavement ants nest under sidewalks, driveways, and concrete slabs. They enter through cracks in the foundation and eat just about everything: meats, pet food, bread, nuts, and sweets. If you have a slab-on-grade home, these are a likely suspect.
Carpenter ants are the ones worth worrying about. They’re larger (up to half an inch) and don’t eat wood, but they chew through it to build tunnels, leaving behind piles of sawdust-like frass. They target moist or rotting wood, including attic beams, areas behind bathroom tiles, subfloor insulation, and hollow spaces like wall voids and door frames. If you’re seeing large black ants consistently, check for water damage in your home. Ignoring carpenter ants can lead to real structural problems.
Cut Off Their Food and Water
Ants send out scouts. When a scout finds food, it lays a chemical trail back to the colony so hundreds of workers can follow. Your goal is to make sure scouts find nothing worth reporting.
Wipe down counters and stovetops after every meal, not just at the end of the day. Crumbs and grease films are enough to trigger a trail. Store sugar, honey, syrup, and cereal in sealed containers rather than leaving them in original packaging. Ripe fruit on the counter is a magnet, especially in warm months.
Pet food is one of the most overlooked attractants. If your dog or cat free-feeds, pick up the bowl between meals or place it in a shallow dish of water to create a moat ants can’t cross. Take garbage out regularly, and use bins with tight-fitting lids both inside and outside.
Moisture matters as much as food, especially for odorous house ants and carpenter ants. Fix leaky faucets, repair dripping pipes under sinks, and make sure your bathroom exhaust fans actually vent to the outside. A chronically damp cabinet under the kitchen sink is practically an invitation.
Seal Every Entry Point
Ants exploit gaps as small as 1/16 of an inch. A systematic walk around your home’s exterior, plus attention to a few indoor spots, can shut down most entry routes.
Start with doors. Lie on the floor and check for light filtering under exterior doors. If you see any, install door sweeps or thresholds, and run a bead of caulk along the bottom outside edge and sides of the threshold. Sliding glass doors are a common weak point; line the bottom track with half-inch to three-quarter-inch foam weatherstripping. For garages, use a rubber bottom seal rather than vinyl, which cracks and shrinks in cold weather.
Next, seal utility openings where pipes and wires enter your foundation or siding. Outdoor faucets, electrical receptacles, gas meters, dryer vents, and cable TV lines all create gaps that ants, spiders, and other pests use freely. Plug these with caulk, urethane expanding foam, or copper mesh, depending on the size of the gap.
For cracks around windows, doors, and fascia boards, use a good quality silicone or acrylic latex caulk. Latex caulks clean up with water and are paintable, which makes them more forgiving for visible areas. Caulks that dry clear hide mistakes better than pigmented ones. Before applying, clean out the crack and remove any old peeling caulk so the new seal actually adheres.
Inside, pay attention to where plumbing enters walls under sinks, where baseboards meet the floor in kitchens and bathrooms, and any cracks in a concrete slab floor. These are the routes pavement ants use most.
Use Bait, Not Spray
This is the single most important principle for actually solving an ant problem rather than just chasing it around your house. Spraying visible ants with a contact insecticide kills the workers you can see, but the colony, which can number in the tens or hundreds of thousands, stays intact underground or in your walls. Some sprays are repellent, meaning they don’t even kill the ants. They just reroute the trail to a different entry point.
Baits work differently. They contain a slow-acting toxicant mixed with something ants want to eat. Workers carry small amounts back to the nest and feed it to other workers, the larvae, and most critically, the queen. Once the queen dies, the colony collapses. This process takes time. You’ll typically see ants for a week or more after placing bait, and that’s actually a good sign. It means workers are still actively ferrying the bait home.
For this to work, you need to resist the urge to spray. Spraying near bait stations kills the workers before they can carry the bait back, which defeats the entire purpose. Place bait stations along active trails and near entry points. Don’t disturb the trails while baiting is underway.
Match the bait to the ant. Sweet-feeding species like odorous house ants respond best to sugar-based gel or liquid baits. Pavement ants, which eat a wider range of foods, may respond better to protein or grease-based baits. If you’re not getting activity on one type, switch to the other.
A Simple Homemade Bait That Works
You can make an effective liquid bait with three ingredients. Mix one teaspoon of boric acid powder with three tablespoons of white table sugar, then add warm distilled or bottled water up to one and three-quarter cups. Stir until everything dissolves completely. Soak cotton balls in the solution and place them near ant trails in shallow dishes or jar lids.
The low concentration of boric acid is key. Too much kills workers before they make it back to the nest. Too little doesn’t affect the colony. This ratio lets ants feed, return home, share the bait through mouth-to-mouth food transfer, and slowly poison the colony from the inside.
A word on safety: boric acid is not harmless. In dogs, ingestion can cause vomiting, diarrhea, excessive drooling, and loss of appetite, with symptoms appearing within about two hours. Young and older animals are more sensitive. If you have pets, place bait stations inside enclosed containers they can’t access, or use commercial bait stations designed to keep pets out. Keep the solution off floors where curious animals might lap it up.
Outdoor Barriers and Prevention
Diatomaceous earth (food-grade, not pool-grade) works as a physical barrier around your home’s perimeter. The powder is made of microscopic fossilized shells with sharp edges that cut through an ant’s waxy outer coating, causing it to dehydrate and die. Sprinkle a thin, continuous line along foundation walls, around entry points, and across known ant trails. The catch is that it only works dry. Rain, sprinkler water, or even heavy humidity renders it useless until it’s reapplied.
Trim tree branches and shrubs that touch your house. These act as bridges that let ants bypass any ground-level barriers entirely. Many ant species feed on the sweet secretions of aphids living on plants, so vegetation touching your siding creates both a food source and a highway indoors. Keep mulch at least a few inches away from your foundation, and pull boards, stones, or debris away from the house perimeter, since odorous house ants and pavement ants nest under these materials.
When a Professional Perimeter Treatment Makes Sense
If you’ve sealed entry points, placed bait, and removed food sources but still see persistent activity, a professional perimeter spray may be the next step. Pest control companies apply residual insecticides around your home’s foundation that continue killing ants on contact for up to 90 days. These products are microencapsulated, meaning they release slowly over time rather than breaking down in the first rain.
Professional treatments are especially worth considering for carpenter ants, where the nest may be deep inside a wall or in structural wood that you can’t easily access or bait. A pest professional can also identify satellite colonies, since carpenter ants often maintain multiple nests connected by trails.
Perimeter treatments work best as one layer in a larger strategy. They stop new ants from crossing the barrier, but they won’t eliminate a colony already nesting inside your walls. For that, you still need bait or direct nest treatment. Think of the perimeter spray as the fence and the bait as the solution.
A Seasonal Routine That Prevents Problems
Ant invasions are predictable. They spike in spring when colonies expand and send out new foragers, and again in late summer and fall when ants stockpile food before winter. A twice-yearly routine handles most situations.
In early spring, walk your home’s exterior and re-caulk any gaps that opened over winter. Reapply diatomaceous earth around the foundation. Place bait stations preemptively along past problem areas before you see the first ant. In late summer, repeat the inspection and refresh outdoor barriers. Inside, do a deep clean of the kitchen, including pulling out the stove and refrigerator to remove grease and crumbs that accumulate out of sight.
Consistency matters more than any single product. Homes that stay ant-free aren’t using a secret weapon. They’re just removing the food, closing the doors, and dealing with colonies before they get established.