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🍁 Built for Canadian homes — written to Canadian codes and provincial rules. Not intended for use outside Canada.
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Ants inside the house

A trail of ants is usually a nuisance, not a disaster — the small ants after your crumbs are a clean-up-and-bait job. The one exception worth knowing is carpenter ants, which can point to damp wood.

tuneWhat are you noticing?
Select anything that matches and the checklist below reorders to fit. Not sure? Skip it.
emergency_home

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Start here

In Canada, most indoor ants are nuisance ants after food — start here. Wipe the trail with soapy water to erase the scent, put away and seal food (including pet food), and clean up crumbs and sticky spills. Then set ant bait stations along the trail and be patient: the ants carry the bait back to the colony, so activity often rises for a day or two before it falls off. Don't spray the trail with a contact killer first — it scatters the colony without reaching the nest.

Ranked from real-world failure data. The order updates as you select what you’re noticing above.

Likely causes, in the order to check them

Showing the typical order
Beginner-friendly Doable, with care Safety-critical Call a pro

visibilityNuisance or carpenter? Follow the trail

  1. Look at size and colour. Small ants (a few millimetres), often brown or black, marching a tidy line to food are nuisance ants — the DIY case. Large (roughly a centimetre) black ants, especially in spring, point toward carpenter ants.
  2. Look under and near wood — window and door frames, baseboards, sills, the deck ledger. Small piles of sawdust-like shavings (frass), sometimes with insect parts, are a carpenter-ant sign. If you find frass or large black ants, stop the DIY plan and read the carpenter-ant note.
  3. For nuisance ants, follow the trail back with a flashlight to where it enters — around a window, under a baseboard, through a gap at a pipe. That entry point is what you'll seal after baiting.
buildflashlight schedule20 min

handymanHow to fix it

Erase the scent trail with soapy water, remove and seal food sources, then set ant bait stations along the trail and leave them undisturbed while foragers carry bait back to the colony. Seal the entry point once activity stops.

  1. Wipe the whole trail and surrounding surfaces with soapy water or a vinegar solution to erase the scent line, and put away every food source — including pet food, sugar, and sticky spills — in sealed containers.
  2. Set ant bait stations right along where the trail ran, following the label. Do NOT spray the trail with a contact killer first — killing foragers scatters the colony and stops them carrying bait home.
  3. Leave the baits undisturbed. Expect activity to rise for a day or two as ants feed and recruit, then drop off over one to two weeks as the colony declines.
  4. Once the ants are gone, caulk or seal the entry point you traced, and keep the area clean and dry so a new colony isn't invited back.
schedule45 min savings$12–30
Ant bait stations (indoor)Pre-filled enclosed bait stations for household ants; child- and pet-resistant styles available Caulk / sealantPaintable interior/exterior caulk to seal gaps at windows, baseboards, and pipe penetrations
warning Use baits by the label — and don't spray the trail firstAnt baits are pesticides: use them exactly per the label, keep them away from children and pets (or use child- and pet-resistant stations), and wash your hands after handling. Just as important, don't spray the visible trail with a contact killer before baiting — it kills the foragers you need to carry bait back and scatters the colony, which makes the problem drag on. Bait first; spray is not the shortcut it looks like.
gavel Check your province first AB: homeowner may do this · BC: homeowner may do this · ON: permit + inspection required · PE: homeowner may do this · QC: permit + inspection required
Setting consumer ant bait stations and sealing entry points is owner-permitted; use only products registered for household use and follow the label.

verifiedWhy this one goes to a pro

Large black ants or sawdust-like frass indoors aren't just a bigger version of the nuisance problem. Carpenter ants nest in wood that's already damp or rotting, so they're a sign of a moisture issue in the structure. Baiting alone won't fix the underlying leak or rot. Have a licensed pest professional treat the nest and, for the wood and water source, a contractor find and repair the damage — catching a hidden leak early is worth far more than the ants themselves.

Your notes travel with the request — what you saw, what you ruled out, when it started — so the pro arrives with a head start instead of a mystery.

verifiedWhy this one goes to a pro

Repeated returns after honest cleaning, sealing, and baiting usually mean the nest is large, hidden, or a species that consumer bait won't clear. That's not a sign to keep buying more bait — a licensed pest professional can identify the species, find the nest, and treat it directly, which is faster and cheaper than months of half-measures.

Your notes travel with the request — what you saw, what you ruled out, when it started — so the pro arrives with a head start instead of a mystery.

sort

Why the list is in this order

We don’t sort by likelihood alone. We sort the way a good, honest tradesperson thinks: rule out the free, safe, common causes first. That’s why the cheap checks outrank the expensive repairs — and why anything dangerous gets a hard stop instead of a pep talk. The order exists to save you money, not to sell you anything.