Mice in NDG Triplexes — Why It Happens and How to Stop It
Notre-Dame-de-Grâce has a mouse problem that rivals Verdun and the Sud-Ouest. Our zone scoring puts most NDG postal codes between 88 and 100 for rodent activity from October through March. The reason is not the people — it is the buildings.
Why NDG triplexes are mouse magnets
NDG's housing stock is dominated by 1920s–1950s brick triplexes and duplexes. These buildings have three structural traits that mice exploit:
- Stone-rubble or brick foundations with mortar that has lost integrity through 80+ winters of freeze-thaw.
- Shared wall cavities between units — once a mouse enters one apartment, it has free run of all three.
- Original cast-iron drain stacks with unsealed pipe penetrations under every kitchen and bathroom.
Add a back alley with garbage cans, a rear yard with a mature tree, and a basement with a furnace room — and you have everything a mouse colony needs.
The five entry points we find on every NDG inspection
- Gas line penetration behind the stove — almost always unsealed.
- Dryer vent — flapper broken or missing on the exterior.
- Foundation/sill plate gap — visible from the basement looking up.
- Garage door bottom seal on triplexes with a rear garage.
- Roof soffit-fascia gap where mice climb the brick and enter the attic.
What NDG owners can do this weekend
- Walk the perimeter at dusk with a flashlight and look for any hole larger than a dime — that is mouse-passable.
- Pack steel wool tightly into every gap you find, then cover with silicone caulk or foam.
- Install a brush-style door sweep on every exterior door.
- Move the bird feeder away from the house — bird seed feeds mice, not just birds.
- If you own a triplex, treat all three units, the basement, and the back yard at the same time. One-unit treatment is wasted money.
When to call a professional
Call when you see droppings in more than one room, hear scratching at night for more than two consecutive nights, or find chewed food packaging. A single mouse rarely operates alone in NDG — the colony averages 6-12 individuals before the first one is spotted.
FAQ
How much does mouse extermination cost in NDG?
A standard residential treatment with three follow-up visits and exclusion runs $350-$650 depending on building size. Triplex-wide programs run $700-$1,400 because all three units are treated together.
How long until mice are gone?
If the entry points are sealed at the same time as treatment, you should see no fresh activity within 14 days. If entry points are not sealed, mice return within 30 days regardless of how much bait is used.
Mice in your NDG home or triplex?
Same-day response. Triplex-wide programs available. English & French.