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How to get rid of carpenter ants in your home?

Fourmis Charpentiere sur bois

Eliminating a colony of ants is no easy task! Over 66 varieties of carpenter ants share the land in the province of Québec, but mostly two to five species are encountered by home owners in Montréal. The two most well-known are the black carpenter ant (Camponotus pennsylvanicus) and the bicoloured (black and red) carpenter ant (Camponotus herculeanus). They are active in all kinds of environments: urban, agricultural, rural, or forested. Even winter won’t scare them away!

How can you get rid of carpenter ants and prevent their return? This small guide aims to provide the necessary information that will help you to push back ants’ presence in your environment.

Detecting the presence of ants

It’s quite normal to find a nest or even a colony of carpenter ants in nature, for example in the ground or in a dead tree stump. Their presence there is even beneficial as they feed on other harmful insects such as lice (aphids).

However, they can become a cause for concern when seen inside our homes. These ants are easily recognized by their rather large size (6 mm to 20 mm), their colour (completely black or chestnut brown and black), and their appearance—they are heftily built, with a large head and powerful jaws.

After June, a few carpenter ants might simply pass through your home, looking for a source of water or food. There is no need to worry at this point, but it’s still prudent to pay more attention to the ants you see: are they increasing in numbers, and do they seem to mostly all follow the same path that leads somewhere under a wall or behind an appliance? If you notice this kind of activity, especially in winter or early spring, it is possible a nest or colony has set up residence somewhere inside a wall or a floor.

The clearest sign that a carpenter ant queen has decided to stay in your home is the emergence of small mounds of sawdust on window sills or doorframes, at the back of cupboards, behind the dishwasher, etc.

Ways to eliminate carpenter ants

To get rid of carpenter ants for good, in all cases it is necessary to find and eliminate the queen in the primary nest (some nests do not harbour a queen and are called satellite nests). It is sometimes possible to eliminate a nest of carpenter ants yourself by:

  • Removing the entire piece of wood in which the nest has embedded itself; this is the most efficient and environmentally friendly way of removing their presence. Beware, however, as the colony could try to move to another spot nearby.
  • If it is not possible to remove the piece of wood for some reason or another, the second solution consists in drilling holes in the wood containing the nest and to fill them with an insecticide that has been approved for use against carpenter ants; an eyedropper can be used, for example. You can also use the approved insecticide on the pathways the ants use regularly, such as window sills and underneath doorframes.
  • Always exercise great care when using any insecticide, as they are designed to kill insects. Carefully read all the instructions on the product label before using it. Check that the product is approved for use against carpenter ants and make sure you fully understand how to mix, apply, conserve or dispose of the product, as well as the precautions to use when handling it. Although Borax is often used, it is far from harmless and is toxic to children and pets.
  • For a nest located outdoors: flood it several times with boiling or soapy water; sprinkle it generously with red pepper, wood ash or diatomaceous earth (a nontoxic natural pesticide made of a silica compound that has been processed to a very fine powder). Even if it is often impossible to eliminate a colony yourself, these steps will help to reduce its size.

The most efficient way to get rid of carpenter ants

As a first step, limiting the access to food and water is essential. Often, eliminating a nest or a colony of carpenter ants yourself isn’t as easy or as simple as people think. It’s true that ants may react to a first or even a second action on your part, and seem to lessen their activity … but it’s probably temporary! They’re just reorganizing in order to better continue their work later. Don’t let them fool you!

Calling on the services of a pest control professional is often the most efficient way of getting carpenter ants off your property. Why?

  • They are authorized to use more powerful insecticides than those sold in stores to the general public. Results are often immediate.
  • They are trained to safely handle and apply insecticides so that you and your family are protected from the dangerous effects of toxic substances.
  • They are trained as to the behaviour of carpenter ants, which helps them to quickly discover where they have built their nest.

How can you prevent them from coming back?

Even if a nest has been successfully eliminated indoors, there is still a risk the ants will try to come back because they live all around us outdoors. Here are a few tips to prevent them from returning indoors to explore:

Outdoors tips to prevent carpenter ants :

  • Repair all cracks or fissures on your home’s cladding.
  • Inspect the roof, soffits and gutters to check for possible water leakage; ants are attracted by damp and rotting wood.
  • Install mosquito netting on all openings that give access into the house.
  • Cut off any tree branches touching the house, and check the cables and cords connected to the house.
  • Remove any damp or rotting wood around the house.
  • Do not store firewood very near the house or on a damp surface.
  • Apply an insecticide which has been approved against carpenter ants on your house’s foundations, soffits, window frames and patio doors; this will keep the ants’ population growth in check within the immediate perimeter of your home.

Indoor tips to prevent carpenter ants :

  • Store food in leakproof containers.
  • Regularly wash kitchen countertops and floors.
  • Do not leave dirty dishes or leftover food on countertops or in the sink, especially at night.
  • Place household trash outdoors in a securely covered garbage container.


Carpenter ants have no secrets for pest control experts in the province of Québec. Don’t hesitate to contact a certified professional from Avalanche Extermination to help you get rid of carpenter ants once and for all.