North Riverdale Comprehensive Rat Control Treatment

Case Study: North Riverdale Rats in the Basement Wall

The following article tells the story of a persistent rat infestation in Riverdale that required multiple visits to solve. This will recount the investigative process and pest control solution carried out by The Exterminators team.

The owners of this Riverdale property reached out to The Exterminators when they heard scratching noises coming from an exterior wall in their basement. What may have seemed like a simple rat problem at first became an extensive project that revealed flaws in the structure of the home. A comprehensive rat control treatment of the infestation has since left this Riverdale household completely rat-free.

Riverdale: A Diverse and Historic Neighborhood

Riverdale Park - Pest problems in riverdale
Given Riverdale’s location many residents experience significant pest control problems

Riverdale is one of Toronto’s largest and oldest neighbourhoods. Sitting east of the Don River Valley, Riverdale stretches between Danforth Avenue, Lake Shore Boulevard, and Leslieville. Riverdale Hospital, which used to be called the House of Refuge, was a primary driver in the construction of the neighbourhood back in the 1800s. Many homes that were built for the working class during this period are still lived in today. Riverdale’s residential landscape thus consists largely of Victorian houses that have been redeveloped into modern, single family and multi-residential homes. Bordering Greektown, Riverdale is also home to many parks, boutiques, restaurants, cafes, and bars that attract locals and tourists alike.

Riverdale’s extensive history and bustling food service industry unfortunately make this neighbourhood a hotspot for pest activity. Old houses, like those in Riverdale, often have obsolete features that enable pests to get around. These structures are also prone to structural damage and deterioration, providing entry points into the home. Renovated properties within Riverdale may still have old pipes and foundations that are susceptible to rat problems.

Initial Inspection

During the first visit, a technician performed a thorough inspection of the home’s interior and exterior. Rodents were suspected to have burrowed under the deck and made their way behind an exterior wall in the basement. The homeowner reported hearing scratching sounds in the wall but had not yet witnessed any activity indoors. No interior points of entry were found at this time, only noises behind the wall.

Inspections are a integral part of our rat extermination services and are needed to give professionals an understanding of the situation and to identify possible entry points. These include cracks in the foundation, siding gaps, wall vents, worn-out weatherstripping, cracks in the window frames, and any other hole or crevice within the structure of a building. Once entry points have been found, they can be sealed off to prevent any more animals from getting inside. Inspecting an infested property not only paints a picture for the technician but allows them to implement a pest control program that is more strategic and therefore more effective.

Initial Measures Taken

In this case, no entry points were found, so the technician placed bait stations in the yard and recommended to the customer that they have their deck and foundation better protected from rat invasions. This would consist of digging around the perimeter of the home and screwing a thick steel mesh into its sides, preventing any rats from digging their way in. Foundations sometimes crack with time, and rats can claw their way through openings. This is common in century homes.

Rat Exclusion on Decks
Our exclusion products and services help barricade the structure from any future.

A few days after the inspection, a technician sealed the deck and foundation off with a 16-gauge, galvanized steel mesh and installed a one-way door to the bottom of the deck to allow rats to exit. Like a trap, the one-way door has a flap that lets rats out in one direction. This would let the animals leave their burrow under the deck but prevent them from coming back. Bait stations, which are locked, tamper-proof containers of rodenticide, were placed near the deck so that any rats that left would consume it and later perish. Bait stations have openings on their sides to allow rats to enter, and the baits within are specially formulated to appeal to rats. Only licensed pest control technicians can provide these stations.

About a month later, rat activity had subsided, and a technician returned to the Riverdale property to clean up after the pests. The one-way door was removed, and the technician cleaned the area, using a commercial-grade fogger to disinfect and deodorize any lingering rat matter. Mesh was installed where the one-way door once was, and bait stations were refilled to suppress the exterior population of rats.

Follow-up Inspection: Why are we Still Hearing Rats?

Rats are hard working pests, determined to survive against all odds. Their territories can stretch across entire neighbourhoods and they breed very quickly, so it can be hard to eliminate an entire colony – especially in old residential areas like Riverdale. Despite the initial measures taken, the rats on this property persisted. A few months after the initial treatment, the homeowner called The Exterminators to say that the noises behind the wall came back.

Because we guarantee every one of our services, a technician came back to the property to inspect once again. The wall in question was closely examined, and the technician used a thermal camera to get a better idea of what was behind the wall. Given that rats were being heard, but not seen, the pests were suspected to be living in the wall and possibly using some old pipes to get around. An opening of the wall was recommended to get to the bottom of this issue. This was not initially recommended because cutting open the walls is a rather invasive procedure. The Exterminators team prefers to eliminate rat issues following a process of elimination, starting with the exterior and moving further in if the problem persists. In most cases, rats go away following the initial treatment.

Interior Cleanup and Exclusion

Following the interior inspection, the technician on-site opened the wall behind which noises had been heard. This would help identify what was going on and allow the technician to clean, disinfect, and reinforce the wall with a rat-proof mesh. Soiled insulation not only decreases the efficacy of the insulation itself but can also attract rodents back to the area given that it is soiled with urine and feces. Installing a galvanized steel mesh along the bottom of the wall would prevent any rats from entering the basement itself. In many cases, rats chew and claw their way into the home by making their way through the wall and breaking in where the wall meets the floor.

Rats Nest Behind Drywall
Rats have been nesting behind the drywall from some time. Our thermal camera inspection reveal the void inside the wall. Once we remove the drywall we can clean all rat matter and restore the insulation

Cutting about a foot or two of drywall off the bottom of the wall revealed a serious amount of rat damage. The insulation within the wall had been torn and crushed and covered in feces. Using a HEPA vacuum, the technician removed all the mess, then thoroughly disinfected the area with a fogger. Two entry points were found in the wall, which were promptly filled with gravel and cement. The technician then installed a wall of mesh where the drywall had been, which would later become part of the wall when a contractor came to rebuild it.

Rat Exclusion on Foundation
We do not use spray foam, or copper mesh. We only use galvanized steel mesh. All our exclusion work is backed by a 2 year warranty.

Hidden Points of Entry: Poor Workmanship and Old Age

Another follow-up visit revealed that rats had burrowed in the other walls as well, and those walls were treated the same. They were opened, cleaned up, and examined closely for points of entry. In the end, the rats that continued to infest this Riverdale home were entering the walls by crawling through some gaps in the cement surrounding the basement structure. Some waterproofing work that had been done years ago left cracks in the cement, allowing rats to burrow into the walls of the house more easily. Once this was identified, the homeowners were advised to seal these entry points off with concrete or mesh. At this point, the rats were gone, but they could always come back within a few years. A contractor was hired to fix this issue some time later when the rats were no longer a problem.


This Riverdale case demonstrates just how persistent rats can be and the importance of having a dedicated rat extermination team. By conducting thorough inspections with each step of the treatment, the technicians involved followed a process of elimination, narrowing the issue further and further down until the root cause of the problem was revealed. Once the waterproofing issue was identified, it could be addressed to prevent this from ever happening again. The exclusion work performed by the Exterminators team will keep this household pest-free for years to come.

The Exterminators vow to get to the bottom of every pest issue, no matter how complicated they may be. If our initial treatment does not eliminate the pests on your property, we will investigate further and do whatever we can. If contractual pests return within the warranty period, we will return at no extra cost. Our pest-proofing services also come with extensive warranties, so you can trust that they will keep pests out.