Centipedes love the same things your basement and bathroom love: steady moisture, shelter, and a reliable food source. If you have recurring sightings sprinting along baseboards or curling under the bathmat, you are not imagining a pattern. These rooms produce predictable microclimates that give house centipedes and their meatier outdoor cousins everything they need. After two decades working as a residential exterminator and troubleshooting damp structures from 1890s stone cellars to new slab construction, I have learned that successful control does not start with a spray bottle. It starts with water, airflow, and patience.
Centipedes are predators. If you have centipedes, you also have something they are hunting: small spiders, silverfish, cockroaches, earwigs, springtails, or the larvae of drain flies. Treating centipedes without addressing their prey means you are mowing the grass without fixing the leaky sprinkler. The methods below focus on basements and bathrooms because that is where conditions are most favorable. They also translate well to utility rooms, laundry closets, and crawlspaces.
Knowing what you are dealing with
Most homeowners see two types. House centipedes, usually 1 to 1.5 inches long with delicate, elongated legs, favor indoor living and can race across tile faster than any bug you will see this year. Stone centipedes and other soil dwellers are thicker, reddish to brown, and typically wander in from foundation beds. The ID matters less than understanding their behavior. Both hunt at night, hide in tight, humid voids by day, and depend on ready prey. In basements, check the cold side of rim joists, the junction of slab and wall, and the mortar lips of old fieldstone. In bathrooms, think under the vanity, behind the toilet, inside overflow openings, and the warm edge beneath a tub apron.
If you are unsure about species or you suspect millipedes instead, look at motion and legs. Centipedes move with a jerky sprint and have one pair of legs per body segment. Millipedes curl up, move like slow trains, and have two pairs per segment. Millipedes are mostly plant detritus feeders and appear in mass migrations after rain. Centipede control focuses on hunting grounds and humidity. Millipede surges call for perimeter drying and exclusion.
Why basements and bathrooms become centipede hotspots
Moisture sets the stage. A basement at 60 percent relative humidity or higher, with a few small condensate drips and a clothes dryer that only kind of vents outside, will support spider webs and springtails in the corners. Once the prey population builds, centipedes arrive. Bathrooms are similar. After a hot shower, a small bathroom without a proper exhaust fan can stay humid for hours. That lingering condensation feeds mildew, which feeds fungus gnats and other tiny insects. Centipedes follow.
Age of structure plays a role. In older basements, uninsulated cold water lines sweat all summer, seeding the mineral stains and dark lines that signal micro-ecosystems. In newer homes, tightly sealed envelopes trap humidity, which means you need active ventilation to dry the space. In both cases, floor drains and sump pits act as permanent oases. I have opened sump lids that felt like a rainforest inside, then watched three house centipedes vanish into the pit wall.
Moisture triage that actually works
This is where most DIY efforts stall. The dehumidifier goes in, the bucket gets emptied, but centipedes keep showing up. Success comes from moving beyond the big, obvious fixes to the small, stubborn sources. Keep this tight, high-yield list handy for basements and bathrooms.
- Set and verify dehumidifier targets at 45 to 50 percent, measured with an independent hygrometer, not the unit’s display. Insulate cold water lines and the AC suction line to stop summer sweating, paying attention to elbows and valves where condensation collects. Extend bath fan runtime to 20 to 30 minutes post shower with a humidity sensing timer switch, and verify the fan exhausts outdoors, not into a soffit or attic. Seal sump lids with gaskets and a clear view port, and water test floor drains with a cup of mineral oil to form an evaporation barrier on the trap. Fix micro leaks and wicking: wax ring dribbles at toilets, loose P-trap unions, weeping shutoff valves, and capillary wicking where wood touches damp concrete.
Those five efforts dry the theater. Give them two to four weeks to influence insect populations. I track baseline and progress with sticky monitors placed at problem points: under the sink, behind the toilet, by the sump, and near the bulkhead door. Date the traps, note captures weekly, and you will see whether you are trending in the right direction.
Exclusion beats reaction
You will not seal a centipede out of a bathroom entirely, but you can reduce traffic dramatically. Basement exclusion pays off even more. The key is to target where walls meet floors, where pipes and wires pass through, and the loose interfaces around access panels. I like a one-two approach. For gaps up to a quarter inch, a high quality paintable acrylic latex caulk with silicone works well around trim and finished areas. For utility penetrations or rough masonry, use copper mesh first, tucked in firmly, then foam or mortar. Copper does not rust and discourages gnawing if rodents are a possibility.
Weatherstripping on basement exterior doors often gets ignored. If night light shows around the perimeter, you have an invitation for every ground insect in the neighborhood. Aim for tight sweeps that meet the threshold, then test at sunset. Turn on the basement lights, step outside, and look for glow lines. If you can see light, insects can smell the cool, damp air.
Bathrooms benefit from clean escutcheon plates with backed silicone at pipe stubs. The loose ring behind a toilet shutoff is a hideout the size of a small hotel for house centipedes. Caulk it. While you are there, check the vanity back panel. Unfinished cutouts with ragged edges leave a highway from wall voids into the room. Neaten cutouts and seal the perimeter of the panel to the wall with a small bead, leaving a removable area only where service access is needed.
Hunting the hunters: removing prey
Because centipedes hunt, your best chemical dollar is often spent on their food. Silverfish, drain flies, small roach nymphs, and spiders sustain indoor populations. In bathrooms, start with the drains. Mechanical cleaning beats any gel. A flexible brush, hot water flushes, a proper hair catcher, and a weekly enzyme cleaner reduce the biofilm that breeds drain pests. If you run a jetted tub, purge the lines monthly according to the manufacturer’s instructions or with a jet line cleaner. Those lines provide dozens of feet of moist surface area that centipedes learn to visit.
In basements, inspect shelving, cardboard storage, and the underside of stair treads. Corrugated boxes host silverfish and cockroach nymphs. Replace with plastic bins and elevate them an inch off the slab on strips of PVC trim or metal shelf feet. If you have a utility sink, check the P-trap for slow seepage and sanitize the splash zone that grows gnats.
A targeted perimeter crack and crevice treatment with a non-repellent insecticide labeled for indoor use can knock down roach nymphs and silverfish without broadcasting spray on open surfaces. Professionals often use formulations in the fipronil or indoxacarb families for roaches and bait gels for cracks. Gel baits placed as pea sized dots inside cabinet hinges, under sink rims, and in utility chases do not contaminate living areas and hit the prey directly. If you prefer organic routes, boric acid dust applied sparingly into wall voids and inaccessible cracks can work as a stomach poison for several prey insects, but take care not to overapply. Visible piles repel insects and track onto surfaces.
Sticky monitors and mechanical control
I do not rely on glue boards to eliminate a centipede population, but I do rely on them to tell me if I am winning. Place them where baseboards meet corners in bathrooms and along expansion joints in basements. Lift the vanity toe kick with a flashlight and slide a monitor just under the lip. You will catch not only centipedes but also a snapshot of the underlying community. If your weekly tally shows two centipedes the first week, one the second, and none by the fourth, your moisture and prey steps are taking hold.
For direct capture, handheld vacuums are your friend. When a client calls their local exterminator for a house centipede sprinting across the bathroom each night, I show them how to keep a small vac on tile so it is within reach. They are fast, but a vac ends the chase immediately without splatter or pesticide.
Insecticides for centipedes, when and how
Centipedes resist casual treatments because their bodies are built for speed and survival. A light mist across the middle of a bathroom floor is not going to do much. Think about where they crawl and hide. The most effective professional approaches rely on crack and crevice applications and perimeter bands near baseboards and utilities, not open broadcast onto floors or counters. Residual pyrethroids like deltamethrin, bifenthrin, or lambda cyhalothrin applied at labeled rates in basement utility zones can suppress activity, especially when used after moisture control. For bathrooms, a light, precise application behind baseboards, under vanity bases, and at tub wall junctions is preferable to any fogging product. Aerosol crack and crevice tips help deliver product into gaps without overspray.
Dusts can be very effective as long as you keep them off open surfaces. Silica aerogel and diatomaceous earth used in small, invisible puffs into voids or behind outlet plates abrade the insect cuticle and dehydrate the pest. The trade off is time. Dusts take days to weeks and work best in combination with the non chemical steps above.
If you have pets or small children, ask for or choose a child safe exterminator approach that emphasizes gel baits for prey species and keeps any residual sprays sealed behind trim lines. Many professional exterminator teams now offer safe pest exterminator options that blend non toxic methods and minimal risk applications. I have shifted a sizable portion of recurring service clients to low impact protocols without sacrificing results, but the key remains moisture and exclusion. No chemical can overcome a sump pit venting into a bathroom or a bath fan that does not exhaust outdoors.
A stepwise plan for homeowners
When I am called for a centipede issue that peaks in the bathroom and basement, I propose a two week sprint that front loads the high value tasks.
- Day 1 to 2: Set dehumidifiers to 45 to 50 percent with an independent hygrometer, install a humidity sensing timer on the bathroom fan, and confirm the fan vents outdoors. Day 3 to 4: Insulate sweating lines, seal the sump lid, oil the floor drain trap, and repair any micro leaks at toilets and sinks. Day 5 to 7: Place sticky monitors in four to six key spots, clean and treat drains with a brush and enzyme cleaner, and replace cardboard with sealed bins. Day 8 to 10: Seal pipe escutcheons and trim gaps, add copper mesh and caulk at utility penetrations, and tighten weatherstripping at the basement door. Day 11 to 14: Apply targeted crack and crevice insecticide or dust in utility zones, use gel bait for prey insects in kitchen and bath cabinets, and continue monitor checks.
By day 14, most homes see a notable drop in sightings. Not zero, but far fewer. Over the next two to four weeks, the reduced prey base and lower humidity push centipedes to forage less and eventually leave or die off.
When to call a professional exterminator
You do not have to go it alone. A licensed exterminator brings two advantages you cannot buy at the home center. First, access to non repellent formulations and delivery tools that reach where you cannot. Second, pattern recognition. Experienced exterminators read a basement like a mechanic reads an engine bay. We spot the faint rust bloom that tells of a seasonal drip, the drywall tape line that waves because the cavity behind it is wet, or the foundation hairline that opens to a utility chase.
If you are in a multi unit building, call a residential exterminator with apartment experience or your property manager’s pest control exterminator. Shared voids mean your prey and your centipedes do not respect party walls. In commercial spaces with restrooms below grade, an office exterminator or commercial exterminator should inspect drain lines and janitorial closets where mop sinks create persistent humidity.
Seek a certified exterminator who can explain the plan and products in plain language. Ask if they offer an eco friendly exterminator or green exterminator program if that matters to you. A trusted exterminator will start with inspection and moisture metrics, not a spray can. Beware anyone promising to eliminate centipedes in a day. You can knock down activity quickly, but long term results hinge on structure and sanitation.
What service and pricing typically look like
Expect an inspection and initial service to take 60 to 120 minutes in an average single family home. A local exterminator will check HVAC condensate routing, sump lids, bath fan exhausts, and utility penetrations, then set monitors and apply targeted treatments. Follow up may be recommended in 3 to 4 weeks. If you are evaluating exterminator cost, geographic differences are large, but for context, a one time exterminator visit focused on centipedes and moisture related pests typically ranges from $150 to $350 for a home, more if rodent control is also needed. Monthly exterminator service is usually overkill for centipedes unless you have an ongoing moisture issue or a broader infestation. A quarterly exterminator service that integrates monitoring and seasonal adjustments is a better fit. If you see nightly centipede activity and cannot sleep, look for a same day exterminator or even a 24 hour exterminator for an emergency visit, but expect a premium.
If you are comparing quotes, set aside the hunt for the cheapest option. An affordable exterminator is one that gets it right the first time, seals what needs sealing, and tells you which contractor to call when the issue is beyond pest control. Many of us coordinate with plumbers for persistent leaks or with waterproofing pros when a foundation is wicking. A reliable exterminator will be clear about those handoffs.
Bathrooms: specific tricks that change outcomes
I learned long ago that a bathroom’s design can doom or save you. Floating vanities with open space beneath stay drier and make visual inspection easy. Toe kick bases trap humidity. If you cannot change the vanity, cut a discreet access in the back panel and seal every edge except that access. Wrap P-trap unions with a thin strip of absorbent tape for a week to check for weeps. Even a teaspoon per day is enough to feed a micro population.
Grout and caulk lines at tub to wall joints deserve attention. Cracked lines let shower water wick into the wall cavity. That moisture does not stream; it sits. Re caulking with a mold resistant silicone, after drying the joint thoroughly, eliminates a hot zone for both mildew and the tiny insects centipedes eat. Ventilation matters more than square footage. A 50 CFM fan in a large bath will not dry it. Check the fan size and upgrade to 80 to 110 CFM if needed, then verify airflow with a tissue test. The tissue should hold flat to the grille when the fan runs.
Finally, mind the bathmat. A thick mat that stays damp becomes a nightly hunting blind. Either switch to quick dry textiles and hang them after use or wash more frequently during humid months.
Basements: the long game
Basements change with seasons. In spring, groundwater rises and the slab cools, boosting relative humidity even if the thermostat says everything is fine. In summer, warm, humid air condenses on cold surfaces. In winter, stack effect can draw air from the basement up through small gaps and create pressure differences that pull in outdoor insects. Your centipede plan should change with the seasons as well.
In spring and summer, keep the dehumidifier running and the condensate exterminator near me draining to a sealed line, not a collection bucket you forget to empty. In late summer, insulate the first 10 to 20 feet of the AC suction line and all cold water runs you can access. In fall, seal exterior penetrations and refresh weatherstripping. In winter, use the dry air to your advantage with more aggressive crack and crevice dusting. I have cut centipede sightings in old stone homes by 80 percent over a season using this rhythm combined with prey reduction.
Pay attention to storage. Metal shelves with wire racks allow airflow. Solid shelves pressed tight to exterior foundation walls collect condensation shadows. Keep stored goods 2 inches from the wall, even if that means losing a little aisle space. If a basement smells earthy or sweet, you have more than centipedes. That smell means mold growth or persistent damp. Bring in a waterproofing contractor for evaluation. A professional exterminator can control symptoms, but water is the root cause.
Safety and product discipline
Homemade mixes and over the counter bombs feel satisfying and often backfire. Total release foggers push insects deeper into voids and spread residues where you do not want them. Many pyrethroid concentrates sold to homeowners list centipedes on the label, but performance depends on placement and preparation. If you are going to self treat, read labels end to end. Wear gloves and a respirator when dusting. Keep kids and pets out until products dry. If you prefer a pet safe exterminator approach, say it plainly when you schedule. Any reputable exterminator company can build a plan around that requirement, from non toxic exterminator techniques like vacuuming and exclusion to carefully targeted low odor residuals.
A quick case from the field
A 1920s bungalow, half height limestone foundation, finished bath over the old coal chute. The owner reported nightly house centipedes, two to three sightings after showers. A previous contractor had sprayed baseboards twice with no improvement. The sink P-trap union wept a few drops per day onto a concealed shelf. The bath fan, a quiet modern unit, exhausted into the eave cavity. The old coal chute behind the vanity had a loose panel that led into a damp void. I sealed the chute edges with copper mesh and mortar, installed a gasketed access panel, corrected the exhaust to vent outdoors, insulated the cold lines, set a 50 percent humidity target with a dehumidifier draining to a sealed standpipe, and replaced cardboard storage with plastic bins on open metal racks. I applied a silica dust in the chute void and a narrow residual band under the vanity. We set six monitors. Week one, four centipedes captured. Week two, one. Week four, zero. The owner kept the fan on a timer and changed nothing else. The difference was not the chemical. It was air and water.
If centipedes are a symptom of something worse
Sometimes centipedes are your only visible clue that a more serious pest is active. I have followed their trail to a hidden German cockroach nest behind a dishwasher panel and to a web farm of cellar spiders above a sump pit. I have found evidence of mice in bulkhead steps because centipedes climbed to hunt the grain weevils nibbling old birdseed. If you catch roach nymphs on your bathroom glue boards or see pepper like droppings under the vanity, call a roach exterminator promptly. If you see shredded insulation or droppings in the basement along sill plates, involve a rodent control exterminator. A comprehensive exterminator service can coordinate multiple targets without over treating your home.
Choosing the right help
Search for an exterminator near me and you will get a page of options. Filter them for licensed exterminator status and membership in a state or national pest association. Read reviews for mention of moisture work, not just quick sprays. A top rated exterminator in my market publishes their moisture targets, posts before and after sump lids, and includes photos of sealed penetrations. That signals process. If you need flexible hours, ask about a fast exterminator service or scheduling a same day exterminator for the first knockdown followed by a calmer, detailed follow up.
Pricing should be transparent. Ask for an exterminator estimate that separates inspection, exclusion work, and chemical applications. If they offer a warranty exterminator service, read what it covers. Most guarantee reductions and retreatments within a window, not a bug free promise. That is reasonable. Bugs fly in through open doors. What you want is a partner who returns and adjusts the plan.
The long tail of prevention
Once you win back your bathroom and basement, keep them. Treat prevention like maintenance. Replace the bath fan filter annually if it has one, and clean the grille. Check dehumidifier performance each spring with that independent hygrometer. Refresh caulk lines, and re oil floor drain traps if the room sits unused. Keep monitors handy and run them for a week each spring and fall. You are not building a fortress, you are maintaining an environment that does not feed centipedes or their prey.
A final note on expectations. Seeing an occasional centipede is normal in many climates, especially after heavy rain or during seasonal shifts. The goal is not to eliminate every single one forever. The goal is to end the patterns that make you dread stepping into the bathroom at night or heading downstairs with the laundry. With moisture as your North Star and a disciplined plan, you can stop the sprints across tile and turn your basement and bathroom back into simple, dry rooms.
If you hit a wall or want a second set of eyes, hiring a professional exterminator is not a defeat. The right technician will do what a good tradesperson does: measure, explain, and fix the root cause. Whether you choose a budget exterminator for a limited scope or a premium exterminator with full exclusion services, insist on clarity. And if your situation changes overnight because of a plumbing leak or flood, do not hesitate to call an emergency exterminator for a short term knockdown while you schedule the plumber. Control is all about sequence. Dry first, deny entry, starve the prey, then treat what remains. That is how you win against centipedes in basements and bathrooms.