How to get rid of
carpenter ants.
How to get rid of carpenter ants: confirm them, find the nest, fix the moisture problem, use bait and keep firewood and branches away from the house. A guide for Toronto homes.
Carpenter ants do not eat wood, but they hollow it out to build nests, usually in wood that is already damp or damaged. Seeing them indoors in late winter or early spring often means a nest is inside the building. Getting rid of them means finding the nest, removing the moisture that attracted them and treating the colony, not just the ants you see.
How to Get Rid of Carpenter Ants:
step by step.
1. Confirm they are carpenter ants
Carpenter ants are large, about 6 to 13 mm, and usually black or black and red, with a smooth, evenly rounded back. Look for piles of fine, sawdust-like debris (often mixed with insect parts) below window frames, baseboards or beams, and faint rustling in walls.
2. Find the nest
Carpenter ants are most active at night. Follow them with a flashlight after dark to see where they go. Check damp wood around windows, doors, roof leaks, bathrooms, decks and porches.
3. Fix the moisture problem
Repair roof and plumbing leaks, clean eavestroughs, improve ventilation in attics and crawl spaces, and replace rotted or water-damaged wood. Without damp wood, carpenter ants have far fewer places to nest.
4. Use bait near the activity
Place carpenter ant bait along the trails where you see them, using a product with a Pest Control Products (PCP) number and following the label. Leave the ants alone while they feed so they carry it back to the nest. Bait can take several weeks.
5. Remove outdoor nesting sites
Keep firewood off the ground and away from the house, remove old stumps and rotting wood nearby, and trim tree branches that touch the roof or walls.
6. Seal entry points
Caulk cracks and gaps around windows, doors, utility lines and the foundation, especially where wood is close to the ground.
Mistakes
to avoid.
- Spraying the ants you see, which does not reach the nest.
- Ignoring sawdust-like debris or rustling in walls.
- Stacking firewood against the house.
- Leaving roof, window or plumbing leaks unrepaired.
When to call
a professional.
Our carpenter ant control service in Toronto costs $350–$500, before HST. Quotes are free, and we are fully licensed and insured.
Call a professional if
- You see large black ants inside in late winter or early spring.
- You find sawdust-like debris or damaged wood.
- You cannot find the nest.
- Ants keep coming back after baiting.
Common questions.
Do carpenter ants eat wood?
No. They chew through wood to make nests and push out the debris, but they feed on other insects and sweet foods such as honeydew.
Are carpenter ants dangerous to my house?
They can damage wood over time, especially when a colony has been active for years. They usually start in wood that is already damp or damaged, so they can also point to a moisture problem.
Are flying ants in spring carpenter ants?
Often, yes. Large winged ants coming out indoors in spring usually mean a carpenter ant colony is nesting in the building. See our carpenter ant control page for help.
Still seeing activity?
Tell us what you are seeing, where and for how long. We will confirm the price before any work starts.
Guidance based on Health Canada: ants. Updated October 10, 2026.