Carpenter Ant Control in Scarborough

Those big black ants marching through a Scarborough kitchen in spring are not the little sugar ants. Carpenter ants set up their colony inside wood, and while they never eat it, they hollow out galleries through damp or rotting framing and, given enough time, they weaken it. Step one is always separating them from termites, since people mix the two up all the time and each calls for a different fix. A typical carpenter ant job lands between $250 and $500, and the reason is simple: you are paying someone to track down a hidden nest, not to mist a trail on the counter. Big black ants indoors plus little heaps of what looks like sawdust almost always means carpenter ants, and it almost always means water is getting into the structure somewhere.

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Carpenter ant or termite? How to tell them apart

Start here, because it changes everything about the treatment and how worried you should be. Scarborough homeowners get a break on this one: termites do turn up in pockets of the GTA, but they are far rarer than carpenter ants, so that large dark insect on your baseboard is almost certainly an ant.

Here is how they differ if you can get a close look:

• Waist. Carpenter ants have a pinched, narrow waist between thorax and abdomen. Termites have a straight, thick body with no waist.
• Antennae. Ant antennae are bent, like an elbow. Termite antennae are straight and look like a string of tiny beads.
• Wings (on the flying ones). Both swarm, but a carpenter ant swarmer has two pairs of wings of different lengths, front pair longer. A termite's four wings are all the same length.
• What they do to wood. Carpenter ants excavate clean, smooth galleries and push the debris out. Termites eat the wood and pack their tunnels with mud. Carpenter ant galleries look sanded; termite damage looks dirty.

Carpenter ants do not eat wood. They excavate it to nest, and the tell is the sawdust they push out, called frass, piling up below the hidden gallery. If you are finding a small cone of coarse sawdust with bits of insect in it, that is frass, and it points almost straight at the nest above it.

Health Canada's Pest Management Regulatory Agency registers the products used for both, and both are worked by a licensed technician, but confirming which insect you have decides the whole plan. If it turns out to be small kitchen ants instead, the general ant control page covers those.

The signs it is carpenter ants

• Large black ants indoors, often a quarter to half an inch long, especially in spring and at night when they forage.
• Frass: small piles of coarse sawdust, sometimes mixed with insect parts and dead ants, under baseboards, in basements, below window frames or in the garage.
• A faint rustling or crackling inside a wall or ceiling void when the house is quiet, the sound of a large colony working the wood.
• Swarmers in May or June: winged carpenter ants gathering at a window are a strong sign of a mature nest inside the structure, not just foragers passing through.
• Ants concentrated around moisture: a leaky roof, a bad window seal, the wood around a bathtub, a damp basement sill. That is where they nest first.

Moisture is the root cause, always

Carpenter ants ignore sound, dry lumber. What draws them is wood that has already gone soft from damp, an old leak, or the start of rot. Scarborough's postwar housing stock hands them plenty of options: the mature treed lots in Guildwood, Cliffside, Cliffcrest, and Highland Creek drop years of shade and leaf litter that keep decks and porches wet, and the low-set basements in those 1950s and 60s bungalows and back-splits hold damp against the sill plate. Add a roof leak into the attic sheathing, a window that has wept into the framing, or a deck ledger that never dries out, and you have the soft wood a colony wants. Find the moisture and you have usually found the nest, or at least the reason it moved in.

How we actually clear carpenter ants

A repeat call almost always traces back to a technician who killed foragers and never located the nest. Hitting the trail does nothing to the colony living in the wall, so finding the nest is the whole job.

1. Inspection (free). We follow the trails, look for frass, sound out the wood, and locate the moisture. Carpenter ants often keep a main nest outdoors, in a stump, woodpile, or fence post, and satellite nests inside the home. We trace both.
2. Find and treat the nest. Once the nest or gallery is located, we treat it directly, and we bait or treat the trails the workers use between the outdoor parent nest and the indoor satellite, so the whole colony is hit, not just the part you saw.
3. Address the source. We tell you the moisture problem feeding them: the leak, the rot, the wood-to-soil contact. Fixing that is what keeps the next colony out.
4. Follow-up. We return to confirm activity has stopped and the frass is not building back up.

Do you need a pro, or can you do it yourself?

This is one of the few pests where the do-it-yourself route almost never lands, because the entire problem is a nest you cannot see. A shelf bait might thin out the foragers for a while, but it will not locate the gallery inside the wall or the parent colony out in the yard, and it leaves the moisture that invited them untouched. Regular big black ants indoors, frass on the floor, or any noise in the walls, that is a call. Our honest do-I-need-an-exterminator guide covers where the line sits.

Common questions

Reviewed August 2026.

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