Managing Carpenter Ant Pests

The presence of carpenter ants doesn't necessarily mean that you have an infestation. Having them around can actually be beneficial because they feed on small insects, honeydew secreted by aphids, and dead or decaying material.

Carpenter ants:

  • Are large ants, about 6-12 mm long
  • Are distinguished from termites by their narrow, wasp-waist
  • Have antennae with an elbow bend in the middle
  • Do not eat wood; they tunnel into it which eventually causes damage
  • Can make their nests in houses or buildings

Nests can be found in:

  • Moist, decaying wood like in rotting stumps and trees, woodpiles, or
  • In houses where wood has begun to rot, or
  • Drier areas like walls, eaves, ceilings, attics and crawl spaces.


The best protection is to maintain dry conditions with proper construction and maintenance:

  • Remove and repair wood damaged by moisture, ventilate damp areas and clean gutters to avoid clogging
  • Store firewood on raised platforms away from the house
  • Prune trees and shrubs so branches don't touch the house
  • Remove all rotted stumps, logs or wood used for landscaping
  • Ensure that wood siding or structures aren't in contact with soil near foundations


If you see more than 10-12 ants in your house in an evening, it’s worth investigating whether their nest is in the house.

  • Identify the ants correctly – if in doubt, trap some and have them identified by a pest control company
  • Find the nest by following the ants as they return to it – sometimes jam or honey will help draw them out
  • Check crawl spaces, attics and under porches for signs of nesting activity (mounds of loose shavings or sawdust)
  • Listen for rustling sounds in the walls

  Possible entryways into a home include:

  • Fence joined to house
  • Plumbing outlets
  • Lower edges of siding
  • Edges of fireplace brick
  • Crawl space vents
  • Gutters
  • Window casings
  • Door frame
  • Vegetation touching house
  • Overhead wires

Getting Rid of Ants

Find and remove the nest material manually or vacuum up the ants. If no structural damage has occurred, prevent ants from re-entering the space by caulking the entry cracks. If structural damage has occurred, repair it and fix any underlying moisture problems.

Kill ants travelling through walls or prevent them from re-entering by using:

  • Boric acid: A stomach poison for insects
  • Diatomaceous earth (silicon dioxide): A non-toxic white powder that kills insects by causing them to dehydrate

To use these insecticides:

  • Use a mask
  • Apply a fine layer to house wiring and plumbing pipes within reach including the wires inside electrical switches/outlets and the main electrical box (remember to turn off the main power and reseal any vapour barrier, if necessary)
  • Keep the insecticide away from children and pets

Severe Infestations

Call a pest control company if you have an established ant infestation or if your home has a greater chance of becoming infested (e.g. in an area surrounded by forest, on an earthen crawl space or with decaying timbers in the foundation). To prevent the problem from recurring after treatment, replace or repair any damaged timbers and correct moisture problems.