Carpenter ants are one of the most destructive structural pests found in BC homes. Unlike termites, they don’t eat wood — they excavate it to build their nests. But the damage they cause is serious, and because it happens inside walls, roof voids, and structural timbers where it can’t be seen, it often goes undetected for years. Here’s a frank guide to what carpenter ants can actually do to your home — and what to do about it.

Table of Contents

What Carpenter Ants Actually Do to Wood

Carpenter ants excavate wood to create smooth, clean galleries for nesting. These galleries run along the grain of the wood, creating interconnected tunnels that hollow out structural timber from the inside. The ants don’t consume the wood — they push it out of the nest as a fine, sawdust-like material called frass. Finding frass near wood is one of the key signs of carpenter ant activity.

In BC, the Western black carpenter ant (Camponotus modoc) is the primary structural pest species. Colonies can contain thousands of workers and multiple satellite nests, all connected through a network of galleries that can spread through an entire structure over several years.

How Much Structural Damage Can They Cause?

The extent of carpenter ant damage depends on two factors: how long the infestation has been present, and what type of wood is affected.

Early infestation (months): Limited gallery excavation, typically in one area. Structural integrity is rarely affected at this stage. Damage may be confined to a single rafter, beam, or wall stud.
Established infestation (1–3 years): Multiple satellite nests, galleries extending through several connected structural members. Weakening of affected timber begins at this stage.
Long-term infestation (3+ years): Extensive network of galleries through roof voids, wall framing, and floor joists. Significant structural weakening possible. Repair costs can run into thousands of dollars.

Carpenter ants preferentially target wood that is already softened by moisture — around roof leaks, in poorly ventilated crawl spaces, around window frames with failing sealant. This is why the worst carpenter ant damage is almost always associated with a pre-existing moisture problem.

Where Carpenter Ants Nest in BC Homes

Knowing where to look is essential for identifying an infestation. Carpenter ant nest sites in BC homes typically include:

Roof voids and rafters, particularly around skylights, chimney flashing, and roof penetrations where moisture enters
Wall voids around windows and exterior doors
Crawl space timbers, especially floor joists and rim joists in damp crawl spaces
Exterior structural wood: deck supports, fascia boards, window frames
Inside hollow interior doors (less common)

Warning Signs of Carpenter Ant Damage

Frass: Piles of coarse, fibrous material resembling sawdust mixed with insect parts, found near or below the nest site
Large black ants inside: Worker foragers 6–12mm long, most active at night
Swarming: Winged reproductive ants (alates) emerging indoors in spring is a sign of a well-established, mature colony
Hollow-sounding wood: Knocking on affected structural timber produces a hollow sound
Rustling sounds: A faint rustling sound inside walls at night, particularly in warm months

The Real Cost of Ignoring Carpenter Ants

Carpenter ant treatment by a professional pest control company costs a fraction of the structural repairs needed once the damage becomes extensive. A typical carpenter ant treatment in BC ranges from a few hundred to around $500. Structural timber repairs, once the damage is significant, can cost $2,000–$10,000 or more depending on what’s affected.

Early treatment is the most cost-effective decision you can make when carpenter ants are suspected.

How Carpenter Ants Are Treated Professionally

Effective carpenter ant control requires locating and treating the nest — not just the foraging workers you can see. Professional treatment typically involves:

Insecticide dust injected into wall voids, roof spaces, and other cavity areas where the nest is located
Residual spray applied to exterior foraging routes and around the building perimeter
Identification and advice on moisture issues that are sustaining the infestation

Consumer products applied to visible worker ants do not reach the nest and do not resolve the infestation.

Professional Carpenter Ant Control in Surrey and the Lower Mainland

Top Line Pest Control treats carpenter ant infestations across Surrey, Langley, Coquitlam, Abbotsford, and the wider Lower Mainland. Our technicians locate the nest, apply targeted treatment, and identify the moisture conditions sustaining the colony.

📞 Call (604) 551-6504 for a carpenter ant assessment and same-day treatment.