A family from Saint-Lambert, on the South Shore of Montreal, sought our services after discovering mouse droppings in the pantry as well as in the space under the kitchen sink. The house, built in the 1970s, has an unfinished crawl space that communicates with several rooms through openings around the heating pipes. Despite the installation of a few caps of expanding foam by the owners themselves, the intrusions persisted season after season. To identify all possible entry routes and not repeat partial interventions, our technicians recommended a residential smoke test to draw a complete picture of all the breaches present in the building envelope.
Methodology of the test in an old residence
In a house of this era, plumbing networks are often made of cast iron or copper pipes with aged joints that gradually crumble. Our exterminator’s team in Saint-Lambert began with a thorough inspection of the crawl space, mapping each wall crossing. Then, the inert smoke machine was connected to the main drain after temporary caps were placed on the siphons. The white, non-toxic smoke spread throughout the network in a few minutes. Fumes were observed around the cold water supply pipe that runs through the foundation wall, at the junction between the kitchen floor and the exterior wall, and behind the water heater in the mechanical room. Each leak was noted, photographed and located on a schematic plan of the house.
One particularly revealing detail was discovered under the back porch: a recess crack in the concrete foundation allowed smoke to exit directly outside the house, confirming that it was a transit corridor for rodents. This type of crack, common in suburban homes on the South Shore such as Saint-Lambert or Longueuil, often goes unnoticed during standard visual inspections. The precision of this detection technique made it possible to precisely target the areas to be corrected without unnecessary work. The crawl space was also inspected with an infrared lamp to identify any traces of recent rodent passages.
Targeted sealing and remedial work
Thanks to the test results, each leak point was treated with the most suitable material. The pipe penetrations received an inflating rubber sleeve tightened by stainless steel hose clamp. The foundation crack was injected with hydrophilic expanding polyurethane and then covered with a waterproof finishing plaster. The professional caulking of the entry points was completed by the addition of an anti-rodent metal plate at the foot of the electrical panel, where a space of one centimetre allowed the passage of young mice. Around the water heater, the spaces between the plumbing pipes and the gypsum partition were padded with high-density steel wool, covered with non-toxic acrylic putty to ensure durability.
A second smoke test carried out forty-eight hours later certified the complete tightness of the envelope. Homeowners were also given advice on long-term maintenance, including annual checking of window seals and inspecting flashings around service entrances. For other concrete examples of our work in the region, check out our smoke test on a rental building or our residential caulking case study.
Preventive results and recommendations
Since the intervention carried out by our extermination specialists in Quebec, the family has not reported any new rodent intrusions. Investing in a rigorous smoke test and professional sealing is significantly more cost-effective than repeated treatments that don’t address the root cause of the problem. For any old residence with unexplained infiltrations, we strongly recommend this prior diagnosis before any disinfestation intervention. There is no need to set bait or traps if the entry routes remain open. A comprehensive prevention plan, adapted to the age and configuration of the property, can then be put in place to protect the house in the long term against the return of pests at each change of season.