The executive director of a professional services office located in an office building in La Prairie, on the South Shore, contacted us after a wasp nest was discovered inside a false ceiling, above the open-concept workspace. The wasps entered the premises through a crack in the joint between the window frame and the concrete slab, causing significant stress among employees and forcing several people to leave their workstations. Brossard, a neighboring city of La Prairie, also experienced sustained wasp activity that same summer, which indicated an increased regional presence. The situation required careful intervention to treat the nest without damaging computer equipment or interrupting business activities for longer than necessary. Our certified extermination company has scheduled an inspection at the end of the day to avoid disrupting working hours.
Inspection and evaluation in office settings
The inspection confirmed that the nest was in the false ceiling, between the acoustic tiles and the concrete slab, about two metres above the work area. By delicately lifting a few tiles from the false ceiling, the technician was able to observe a medium-sized, spherical nest suspended from the metal hangers of the suspended ceiling. The nest was light grey in colour, papery in texture, with a single entrance clearly visible on the underside. The species identified was the yellow-legged wasp, whose colonies in confined spaces can become very aggressive during maintenance interventions or when raising false ceiling tiles, which explains the frequency of stings reported by staff. A check of the attic and the outer periphery of the building made it possible to exclude the presence of other active nests on the site. Our specialized technician in the office environment proposed an intervention protocol that minimizes the disruption of activities.
Treatment of the nest in false ceilings
The treatment was carried out in the evening, after all employees had left. Computer equipment and sensitive documents had been covered with protective tarpaulins by the staff before leaving the premises. The technician began by spraying a thin layer of fast-acting liquid insecticide directly onto the nest entrance to neutralize the workers in flight, and then injected long-afterglow insecticidal powder into the nest through the main opening. All the false ceiling tiles around the nest were sprayed on the periphery to intercept individuals that could have escaped during the treatment. The crack in the window seal, the wasps’ access point to the premises, was temporarily plugged with expanding foam to prevent migration to the workspace overnight after treatment. The extermination of wasps in an office space requires this surgical precision to avoid any incidents with personnel or equipment.
Nest removal and ongoing preventive measures
The next morning, before the offices opened, our technician removed the inactive nest from the false ceiling, replaced the acoustic tiles and inspected the entire treated area to confirm the absence of any residual activity. The window seal has been permanently sealed with a durable, temperature-resistant and weather-resistant caulking of the entry points . A report was submitted to the Administrative Director with recommendations for future maintenance inspections of the building, including the annual verification of window seals at altitude and transition points between different façade materials. We have also proposed the installation of a pest prevention plan covering the entire building for the coming seasons. To see more examples of our workplace interventions, read our work on a wasp treatment in a professional space and our work on a hornet’s nest in a similar context. Thanks to our quick and efficient intervention, employees were able to return to their workstations as soon as the office opened the following morning, without any signs of wasps on the premises.