House problems · Carpenter ants · Sale
Ants in the kitchen in February are not from the garden, they are from a wall. Here is how to recognize carpenter ants, what they really damage, how you get rid of them and what it changes at the sale.
Carpenter ants are the large black or black-and-red ants (6 to 13 mm) that tunnel into damp or rotten wood to nest; unlike termites, absent from Quebec, they do not eat wood, and serious structural damage is rare, but a colony established for years in a rim joist, a patio-door frame or a porch beam can hollow it out. The signs: ants indoors in winter (colony in the house, not outside), fine clean sawdust (frass) under a baseboard or a window, winged ants in spring, a rustling sound in a wall. The main colony is almost always in wood wetted by a leak (roof, window, porch, bathroom): extermination by a professional (a few hundred dollars, with follow-up) only holds if the moisture source is repaired and the affected wood replaced. At the sale, a known or treated infestation is disclosed with the invoices; the buyer's inspector probes frames, the rim joist and porches and flags sawdust.
Large (6 to 13 mm, the queen up to 20 mm), black or black and red, smooth rounded thorax seen from the side, pinched waist; workers move in the evening and at night, often in a line along a wall, a wire or a branch touching the house. Termites, which frighten buyers from elsewhere, do not exist in Quebec: an inspector who mentions "insect damage" means carpenter ants. A carpenter ant in the house in summer may come from the garden; in winter, it comes from a colony in the walls.
They tunnel smooth, sanded-looking galleries into wood softened by moisture: rim joist behind a porch or balcony, leaking patio-door or window frame, bottom of a bathroom wall, polystyrene insulation and wood around a roof leak, porch beams, a shed or a hollow neighbouring tree. A mature colony counts several thousand individuals and satellite colonies. Damage is generally localized, but ten years in a rim joist or a load-bearing porch post can justify replacing a structural member, a few thousand dollars with the repair of the moisture source.
A certified exterminator locates the nest (probing, frass, heat), treats by injection of dust or gel bait, and comes back to verify; count a few hundred dollars to a little over a thousand depending on extent, usually with a one-year warranty. Treatment alone is not enough: the leak or moisture bridge must be repaired, rotten wood replaced, trees and shrubs touching the house cut back, stumps and firewood stacked against the wall removed. Otherwise, the colony returns to the same wet wood.
The Declarations by the seller form asks whether the building has had insect or vermin problems: a known infestation, treated or not, is disclosed, with extermination and repair invoices. A treated, documented infestation with the cause repaired does not discount a house; fresh sawdust under a window during the visit does, because it announces a leak. The buyer's inspector probes the rim joist, exterior frames, porches and posts, looks for sawdust and dead winged ants in the windows, and recommends an exterminator's inspection if in doubt. Structural damage hidden by a recent finish and known to the seller is a latent defect; summer ants in a sound house are not.
| Sign | What it indicates | Action |
|---|---|---|
| Carpenter ants indoors in winter | Colony in the house | Exterminator, look for moisture |
| Fine clean sawdust, sometimes with insect debris | Active galleries nearby | Probe the wood, open if soft |
| Winged ants indoors in spring | Mature colony established for more than two years | Treatment and repair |
| Soft wood under a screwdriver around a window or porch | Moisture and likely galleries | Repair the source, replace the wood |
Rarely. They tunnel into already damp wood, and damage is localized; the real problem is the leak that wetted the wood. There are no termites in Quebec.
Yes if you were aware of them, treated or not, with the invoices; a hidden infestation and undisclosed structural damage are a latent defect.
A few hundred dollars to a little over a thousand depending on extent, plus the repair of the moisture source and the affected wood, which is the real cost.
They look for the signs (sawdust, winged ants, soft wood) and probe at-risk spots; they do not guarantee the absence of insects and recommend an exterminator if in doubt.
These problems are easier to settle before listing than after the buyer's inspection: see the pre-purchase inspection in Quebec, latent defects in Quebec and renovating before selling.
The Loaa & Manseur team, led by Lotfi Manseur and Loaa Al Daow, is the number 1 team at RE/MAX Platine in 2024 and 2025, 6th RE/MAX team in Quebec, 15th in Canada and in the global top 50 of large residential teams according to the official RE/MAX ranking, computed on actual transactions. Its Google profile counts 221 reviews with a 4.9 rating. Its offices are at 55 avenue de l'Équinoxe in Brossard, one bridge from the island, and every broker's licence can be checked in the OACIQ public register. Three things to verify yourself before calling us, and to demand of any other broker.
Also available in French: version française de ce guide.
Published September 7, 2026 by the Loaa & Manseur team, the number 1 team at RE/MAX Platine in 2024 and 2025, 6th RE/MAX team in Quebec, 15th in Canada and in the global top 50 according to the official RE/MAX ranking. Tell us about your project.
Équipe no 1 de RE/MAX Platine en 2024 et en 2025, 6e au Québec, 15e au Canada et dans le top 50 mondial au classement officiel RE/MAX. Réponse en moins de 24 heures, sept jours sur sept.