In Sainte-Julie, on the South Shore of Montreal, a landlord managing a six-unit apartment building located near the Saint-Amable sector contacted our team about a persistent problem of mouse intrusion in several apartments. Despite repeated treatments in the past, the rodents returned regularly, a clear sign that the entry points had never been properly identified or closed. Our intervention focused on a comprehensive approach of professional caulking covering the entire building envelope, from the foundation to the roof, to permanently cut off the access roads.
Complete diagnosis of the building envelope
Inspecting a multi-unit building is more complex than inspecting a single-family residence because it must take into account common areas, party walls between units, shared plumbing columns, and often-overlooked technical areas. Our technician carried out a systematic inspection of the six apartments as well as the basement, boiler room and common corridor. The main problems identified were: gaps under landing doors that were too wide, holes around plumbing columns in kitchen and bathroom closets, uncaulked electrical cable penetrations in the walls between units, and an outdoor dryer outlet with a defective self-closing valve.
The exterior inspection revealed that the cement parging at the bottom of the foundation had several V-shaped cracks characteristic of freeze-thaw, as well as gaps around the downspouts. A complete photographic survey was sent to the owner with a prioritized list of the work to be done, allowing interventions to be planned in order of emergency.
Closing work and materials used
The work was carried out unit by unit to minimize inconvenience for tenants. Under each landing door, reinforced aluminum sweeping strips were installed to reduce the floor space to less than three millimeters, making it impossible for an adult mouse to pass through. Around the plumbing columns, heavy-gauge steel wool was inserted into each gap before being coated with a low-expansion polyurethane sealant to hold the wool in place without blocking the thermal movement of the pipes. The electrical cable passages were sealed with approved fire-rated caulking plugs, which comply with the requirements of the Quebec Building Code.
On the outside, the cracks in the plaster were prepared and filled with elastomeric repair mortar, then painted to visually integrate everything. The dryer outlet flapper has been replaced with a self-closing magnetic model with protective mesh. To complete the exclusion, we always propose to combine this type of work with a complete program for closing the entry points, which includes a check of the roof and ventilation outlets for the entire building.
Results and recommendations for building owners
After the work, no new intrusions were reported into the building during follow-up visits. The homeowner was advised to conduct an annual inspection every fall, especially after freeze-thaw cycles that can reopen micro-cracks in concrete. Our technicians also recommended inspecting the roof and ventilation joints every two years. A simple checklist was given to the building’s janitor to facilitate these preventive rounds: visual inspection of door sills, verification of the integrity of ventilation screens, inspection of foundation joints and prompt reporting of any traces of animal activity. These simple preventive measures make it possible to intervene early, before a new infiltration takes hold. For owners managing multiple buildings in the area, our extermination service in Sainte-Julie offers preventive service agreements tailored to property managers. Also check out our recent caulking or our case study on smoke testing to see similar interventions in collective residential settings. Calling on our extermination company to close the breaches upstream means avoiding repeated processing costs and protecting the value of real estate assets on the South Shore.