Centipedes in Your Basement? Here's What They're Actually Telling You

Seeing a centipede in your basement means two conditions already exist in your home: excess moisture and an existing population of smaller insects for it to hunt. The centipede itself is not the infestation — it's a predator that followed a food source indoors through a foundation gap or utility entry point. Spraying the centipede does nothing to remove either underlying condition.

Why Centipedes Show Up in the First Place

I get calls almost every week from homeowners across Durham, York, Peel, and the GTA who saw "a huge bug with a hundred legs" run across the basement floor at night. The reaction is always the same — panic, then a spray can. But a centipede sighting is actually useful information if you know how to read it.

Centipedes are built differently than most insects. Unlike insects, centipedes are not equipped with a wax-like, water-resistant outer layer called a cuticle, so they are more susceptible to water loss through evaporation. That single biological fact explains almost everything about where you find them and why.

Because they lose water so easily, they require relative humidity above 60% for survival and 75%+ for optimal activity. A basement, crawl space, or bathroom with poor airflow hits those numbers easily, especially in Ontario's humid summers or after a wet spring.

But moisture alone doesn't explain why they're inside your walls instead of outside under a rock. Centipedes congregate where there are large amounts of insects and seek out dark, damp places with plenty of small crevices and cracks, like basements, garages, and mulched gardens. They are following prey — silverfish, drain flies, ants, spiders, and other small insects that are already living inside the structure. In my experience running jobs across Simcoe County and the GTA, a home with a steady centipede sighting almost never has an isolated centipede problem. It has an insect population problem with a moisture problem sitting on top of it.

Are Centipedes in Ontario Homes Actually Dangerous?

No, and this is worth saying plainly because it changes how you should approach treatment. Despite being unattractive, centipedes do not pose any real danger to humans, and neither centipedes nor millipedes are able to carry or spread diseases to plants, pets, or humans. Although centipedes have poisonous glands and may bite, their venom is not poisonous to humans or pets, and the type found in Canadian homes typically does not have the jaw strength required to pierce the skin easily.

So the reason to treat them isn't personal safety. It's what their presence tells you about the rest of the structure — active moisture, active insect prey, and open entry points. Ignore those three things and the centipedes are just the visible tip of a bigger problem.

Why Spraying Baseboards Alone Never Fixes It

Most of the "customer sprayed and it came back in two weeks" calls I get are from people who treated the visible bug, not the source. Here's the problem with that approach:

• Centipedes don't originate inside your home. They enter through cracks in the foundation, gaps around pipes, window frames, door sweeps, and utility penetrations — same as the prey insects they're chasing.
• A can of store-bought spray only kills what it touches. It does nothing to the entry points that are still wide open, and it does nothing to the insect population living inside wall voids.
• Moisture doesn't go away on its own. If humidity in the basement stays above that 60% threshold, the environment stays livable for centipedes no matter how many you spray.

This is exactly why baseboard-only treatments fail on a two-week timeline. The technician treated the symptom in the living space and left the actual source — moisture, prey insects, and open entry points — completely untouched.

How We Actually Treat a Centipede Problem

At AstraHive, we don't treat centipedes as a one-step spray job because they're not a one-step problem. Our process addresses the insect population, the entry points, and the structure itself:

1. Exterior perimeter spray. We apply a full barrier treatment around the entire foundation, all windows, doors, and visible entry points. This is a Health Canada approved product, safe for kids and pets once dry, and it stays active for 90 days.
2. Interior spray. We treat interior baseboards, cracks, crevices, under sinks, and known movement zones to eliminate what's already active inside — including the smaller insects centipedes are feeding on. This layer also stays active for 90 days.
3. Wall void dusting. This is the step most companies skip. We inject professional pesticide dust into interior and exterior wall voids, which stays active for up to a year — far longer than any spray. Since centipedes and their prey travel through these voids, this is often where the real population lives.
4. Full documentation. Every job includes a service report noting where activity was found, what species were present, and which products were used.

We back every job with a 100% satisfaction guarantee — if centipedes come back within the warranty period, so do we, at no additional cost. Spider and general crawling insect treatments with us typically starts at $300 CAD depending on the size of the property and severity of activity; because centipede jobs vary a lot based on moisture source and how many wall voids need dusting, call 905-925-8427 and I'll give you a straight quote after hearing what you're seeing.

What You Can Do Before We Get There

A few things genuinely help reduce centipede activity even before a professional treatment, because they attack the moisture side of the equation:

• Run a dehumidifier in the basement to keep humidity below the 60% threshold centipedes need to survive.
• Check and refill any dried-out floor drain traps — dry traps are a common entry point, not just a moisture source.
• Pull mulch and organic debris back from the foundation walls outside.
• Fix any leaking pipes or window well drainage issues before they turn into a standing-water problem indoors.

None of this replaces sealing entry points and treating the wall voids, but it makes any treatment we do last longer.

Why This Matters More in Ontario Basements Specifically

Ontario's humid summer months and older housing stock across Durham, York, Peel, and Simcoe County create ideal conditions — finished basements with poor ventilation, older foundations with more settling cracks, and window wells that collect rainwater. I've been running AstraHive since 2015, and the pattern is consistent: the older the foundation and the more finished the basement, the more likely we find both moisture and an established insect population feeding the centipedes we're called out for.

We're licensed by the Ontario Ministry of the Environment, Conservation and Parks, and we serve 75+ cities across the Greater Toronto Area. Same-day service is available, and we call back within 5 minutes of your message.

Why Choose AstraHive

• Licensed & Insured: Certified by the Ontario Ministry of Environment, Conservation and Parks.
• Fast response: Same-day service available, with a callback within 5 minutes.
• 100% Satisfaction Guarantee: If pests come back, we re-treat at no additional charge.
• Proven track record: 5.0 stars on Google across 150+ reviews.
• Family & pet safe: Health Canada approved products on every job.

Frequently Asked Questions

Do house centipedes mean I have a bigger infestation?

Yes, in most cases. Centipedes are predators that only stay where there's enough prey to sustain them, so a recurring centipede sighting usually points to an existing population of silverfish, drain flies, ants, or other small insects already living inside your home. Treating just the centipede without addressing that underlying insect population is why they keep coming back.

Are house centipedes dangerous to pets or kids?

No. House centipedes cannot spread disease and their venom is not considered dangerous to humans or pets, and the species commonly found in Canadian homes rarely has the jaw strength to break skin. They're a nuisance and a diagnostic sign of moisture and prey insects, not a health hazard.

Why do I keep finding centipedes in my basement specifically?

Basements combine the two things centipedes physiologically need: high humidity and hiding spots near cracks, crevices, and floor drains. Because centipedes lack a waterproof outer layer, they lose water quickly in dry air, so damp basements with limited airflow become one of the few livable environments in the house.

Will a store-bought spray get rid of centipedes permanently?

Usually not for long. Baseboard sprays only kill what they directly contact and do nothing to close foundation cracks, gaps around pipes, or other entry points, and they don't touch the insect population living inside wall voids. That's why many homeowners see centipedes return within a couple of weeks of spraying on their own.

How does AstraHive treat a centipede problem differently?

We treat interior and exterior together rather than just spraying baseboards. That includes a 90-day exterior perimeter barrier, a 90-day interior spray, and pesticide dust injected into wall voids that stays active for up to a year, backed by a 100% satisfaction guarantee with free re-treatment if activity returns.

Sources

• Environmental Pest Control (Ontario) — Centipedes lack a waterproof cuticle, which makes them prone to water loss and drives them to seek damp environments like basements.
• Environmental Pest Control (Ontario) — Centipedes are not known to carry or spread disease to humans or pets, and their venom is not considered dangerous to people.
• Orkin Canada — Centipedes congregate in areas with large insect populations and dark, damp conditions such as basements and garages.
• Aptive Pest Control — Centipedes require relative humidity above 60% for survival and above 75% for optimal activity.

Areas We Serve

AstraHive Pest Control proudly serves 75+ communities across the following regions:

• Toronto: Toronto, North York, Scarborough, Etobicoke, East York, York, Leslieville, Lakeview
• Durham Region: Oshawa, Whitby, Ajax, Pickering, Clarington, Bowmanville, Courtice, Newcastle, Port Perry, Brooklin, Uxbridge, Scugog, Brock, Seaton
• York Region: Vaughan, Markham, Richmond Hill, Aurora, Newmarket, Thornhill, Woodbridge, Kleinburg, Maple, Stouffville, Unionville, Keswick, Holland Landing, East Gwillimbury, Georgina, King City, King Township, Nobleton, Berczy Village, Cathedraltown, Commerce Valley, Cornell, Wismer, Whitchurch-Stouffville, Sutton, Schomberg
• Peel Region: Mississauga, Brampton, Caledon, Malton, Port Credit, Streetsville, Meadowvale, Cooksville, Bolton, Palgrave
• Extended Service Area: Peterborough, Lindsay, Port Hope, Barrie, Bradford, Innisfil, Collingwood, Wasaga Beach, Orillia, Burlington, Oakville, Milton, Hamilton, Grimsby, St. Catharines, Welland, Niagara Falls

Don't see your city listed? Call us — we likely cover it.