In Carignan, on the South Shore, a country residence with an unfinished basement, located on the edge of a wooded area near Chambly, showed signs of infestation by groundhogs. These burrowing animals had dug burrows under the foundation slab and entered the crawl space, where they had left behind piles of droppings, food residue and a strong smell of ammonia. The situation compromised the indoor air quality, with odours coming up to the living room through the floor joints, and could affect the stability of the foundation in the long term. Our team in Carignan has been mandated for a complete decontamination and the implementation of sustainable exclusion measures. At Nova Extermination, we regularly intervene in this rural area of the South Shore for problems related to burrowing animals and their impact on residential buildings.
Crawl space and associated risk assessment
Inspection of the crawl space revealed a concentration of marmot droppings over an area of about twenty square meters. Interior burrows had been dug into the rammed earth to a depth of thirty to fifty centimeters, which had disturbed the perimeter of the concrete slab on at least three sides. Accumulations of plants collected as nesting material, as well as two carcasses of decomposing marmots, were found in the least accessible corners of the crawl space. The high humidity generated by the decomposition of organic matter had encouraged the development of mould on the wooden joists of the floor structure. The odours were spreading to the living rooms via the air intakes and cracks in the laminate floor. A humidity test confirmed levels exceeding seventy percent in the crawl space, well above the recommended threshold of forty to fifty percent to preserve the integrity of the structural timber. This documentation made it possible to establish an intervention protocol adapted to the seriousness of the situation. Our decontamination service also covers this type of confined space that is difficult to access.
Mould removal, disinfection and treatment
The carcasses and accumulated organic matter were first removed in airtight containers, following the required personal protection protocol. The earthen surfaces were covered with a thick waterproof geotextile to block the rise of water vapour and discourage further digging. The joists with mould were treated by mechanical sandblasting and then application of a deep fungicide, followed by a wood consolidation treatment based on boiled linseed oil to restore the strength of the fibres degraded by moisture. The concrete surfaces of the foundation were applied with a high-concentration alkaline disinfectant to neutralize pathogens present in the droppings. Temporary mechanical ventilation of the crawl space was maintained for forty-eight hours to bring the humidity level back to acceptable levels. Treating secondary mold is inseparable from successful decontamination, as skipping this step inevitably leads to structural problems in the medium term. Additional unsanitary cleaning was also carried out in an adjacent storage area that showed traces of cross-contamination.
Permanent exclusion, consolidation and prevention
The burrows dug under the foundation were filled with compacted gravel mixed with dry concrete, a technique that resists new digging efforts by determined animals. A tightly meshed galvanized mesh burrowing deck was buried forty centimeters deep around the entire perimeter of the foundation, forming a continuous and durable physical barrier. Access to the crawl space has been secured with lockable metal doors resistant to intrusion attempts. The owners have received detailed recommendations for the maintenance of the perimeter of their land: regular clearing of brush within thirty centimetres of the foundation, removal of piles of stones and wood likely to shelter marmots or other burrowers. Check out our other residential decontamination projects and preventive projects for solutions adapted to your property on the South Shore.