Case Study: Stubborn Rats in Riverdale

This case study will cover a stubborn rat infestation in the Riverdale neighbourhood which had been looked at by other pest control providers prior to our involvement. Over a period of over two years, we were asked to come back to the same home to deal with rats that had been freely roaming through the walls, ceilings, and floors of a semi-detached home. Although our initial assessment appeared to have identified the source of the problem, the rats constantly found other ways into the home. Our technicians devised a plan to strategically eliminate entry points area by area in hopes to find the main entrance for the rats into the structure. In the end, we were able to exterminate the rats from this home.
The Riverdale neighbourhood in Toronto sits along the Don River and is bordered to the south by Lake Ontario. Predominantly a residential neighbourhood, Riverdale is filled with century-old homes and various small businesses along main streets.
Home to several parks such as the beautiful Riverdale Park with its popular steep ravine, this neighbourhood has attracted many new families and businesses. It is considered an up-and-coming area for many diverse restaurants and art shops.

riverdale park
Riverdale Park, Toronto

Inspection for Rat Intrusion

We were first contacted by the homeowner in 2018 and were informed that there seemed to be a high level of rat activity both inside and outside the home. The house, located at a corner lot, is attached to another house on one side.

wall vents allow rats entry into home
High rat activity was observed in and around this wall vent.

Our certified and licensed technician arrived at the home a preformed a thorough inspection of the inside of the home. Droppings were seen in the kitchen area, confirming that activity is taking place indoors.
Outside the home, our technician identified a few potential entry points. One along the base of the rear wall and a few wall vents that could be used by the rats to enter the home. One of the vents had its mesh screen breached and droppings were present inside.

Initial Steps

The technician placed several snap traps in the home on the surfaces that appeared to be the most active. These traps are used to attract and kill the rats in a humane and quick manner as opposed to poison traps that can take weeks to kill the animal.

rat bait stations in riverdale toronto
Rat bait-stations were placed around the perimeter of the home.

Around the yard, we placed two bait-stations near the potential entry points into the home. These bait-station are filled with commercial grade rodenticide and are meant to kill the rats over time. Eliminating the outside infestation is key to keeping rats out of the home.

Full Rat Exclusion- Interior and Exterior

Our team returned soon after to seal and secure all entry points in the hopes to keep the rats from entering. To do so, we covered the compromised area of the wall with six feet of galvanized steel mesh. This mesh is durable and strong enough to withstand any gnawing by rats or other animals.

wall vent covers protect agains rat intrusion
Wall vents were protected with galvanized steel mesh covers.

Steel mesh covers were also installed to protect all wall vents. A one-way-door was placed in the vent that showed the most activity. These doors, which are made of the same galvanized steel mesh, are designed to allow the animals to exit the structure and not be able to re-enter.

rat one way door installation
A rat one-way door was installed to allow any animals remaining inside to exit in a safe manner.

Follow-up Visits

We returned a few weeks later to remove and seal the one-way-door installed during the exclusion work. An inspection of the bait-stations showed that the animals were still quite active around the yard. Our technician refilled them all with bait at that point.
A month after our last visit, the homeowner called us to advise there was still rat activity in the house. We returned to re-arm all snap traps and refill the bait-stations. Our technician preformed another inspection of the exterior and although we did not find any obvious points of entry, we suspected there may be a hidden entrance into the home structure.
We followed up with the owner several months later and on our visit, we found rats caught by the snap traps. Homeowner informed us that there was still activity and that the basement tenant frequently heard scratching noises from the walls.
A subsequent visit showed no activity at all inside the home, although the noises were present in the walls. Outside, a potential entry point was identified where the house next door intersects with this house- a crack just wide enough that rats could squeeze in. We proceeded to cover and seal the area with three feet of galvanized steel mesh with a one-way-door.

exterior rat exclusion in riverdale
An additional area of the wall is protected with galvanized steel mesh.

At this point we became suspicious of the property next door, where rats were also seen walking through the yards. Because the houses are attached, it is possible for rats to burrow under the neighbour’s deck and into their walls and then make their way into the customer’s home through the house connection.
it is possible for the rats to penetrate from one wall to another through the home connection. They can even burrow from one property to the other from underneath a deck or porch.
With the owner’s permission, we inspected the house next door. The interior showed not rat activity and outside it appeared that the rear deck had been partially sealed with mesh. We decided to patch the few gaps.
On a follow up visit, we found that rats had once again entered the home. Droppings were present under the kitchen island, and the scratching noises from the walls had become more frequent. The bait-stations also confirmed that activity continued outside.
At this point we installed a trail camera in the yard to track any activity and try to pinpoint where the rats were entering the property. We also added a bait-station by the one-way-door to target any rats exiting the property.
The wall noises continued.
When we next returned, the homeowner informed us she had found some pipes going into the home after cleaning out the area. A large gap was seen surrounding one of the pipes. We immediately sealed the gap and installed a one-way-door. We were hopeful that this was the primary entry point and that the problem would be resolved.

wall gaps allow rats entry into home
During our thorough inspection, a large gap was discovered around a pipe entering the home.

Although we hope to find access to all areas of a home, both inside and outside, it can sometimes be difficult to do so because of cluttered rooms or piles of bricks against a wall, for example.
On our next visit a few months later, we found very little evidence of activity both inside and outside. But after discovering a hidden pipe behind the wall, the homeowner requested that we investigate and seal the interior of the basement.

basement water pipe rat entry
An unused water pipe was discovered in the basement.

We removed 26ft. of drywall in the basement and found a considerable amount of debris and droppings. After cleaning and deodorizing, we installed galvanized steel mesh along the entire stretch of the wall to prevent the animals from entering the structure. The hidden pipe proved to be an old unused pipe that had been left behind and we sealed it.

insulation damaged by rats
Debris and rat droppings were seen behind the drywall where the insulation had been damaged.

The wall noises persisted.
At this point we suggested that a full exclusion of the outside and inside would be the only way to prevent the rats from getting into the walls. We also suggested that an exclusion should be done at the neighbour’s rear deck which we suspected was the entry point into the property next door and subsequently into the walls of the customer’s house.
The customer agreed and proceeded with the work. A total of 48ft. of mesh was used to secure the perimeter of the property and 27ft. to secure the neighbour’s deck. To install this mesh, we dig a trench along the base of the walls and then secure it with stainless steel bolts and washers. This will prevent the rats from digging under the surface and attempt to breach the wall.

interior rat proofing
A section of the basement wall is protected from intrusion with galvanized steel mesh.
interior exclusion of rats in riverdale
The inside of the walls were protected with galvanized steel mesh to prevent entry by the rats.

The next-door neighbour also agreed to the placement of bait-stations in her backyard.

rat exclusion in riverdale toronto
The neighbour’s deck area is protected by mesh (left) as well as the full perimeter of the house.


We returned several times afterwards to rebait the stations in the yard. After six months we noted that the activity had subsided considerably. No activity inside the home and the bait-stations on the property were still full.
A check of the neighbour’s bait-station did show high activity. At this point the customer is considering talking with homeowners on her street to try and get them to install bait stations in their own yards.


This rat infestation in Riverdale is a perfect example of how sometimes we must be patient and work through the problem in a concise and logical way. We do not want to preform work that may not be required during the initial steps. We tackle the issue based on experience and knowledge of the pest’s behaviours. The most obvious steps were taken to eliminate the issue, but clearly that was not enough.
It became clear that the home was being breached from an entry point that was not clear. Our suspicion was that the neighbour’s wall under the deck was compromised and the animals were entering through the neighbouring walls. The hidden pipe in the basement also proved to be a main point of entry.
After securing the entire property, as a last course of action, the homeowner is satisfied that the rats are no longer in the house. But with activity still present outside the home, there is always a concern that they may gain entry again.