case study squirrels damage roof and roof vents in markham

Case Study: Squirrels Damage Roof and Roof Vents in Markham

This case study outlines a squirrel removal in Markham where the squirrels had chewed through the roof vents as well as an old temporary roof repair that had been performed years ago by the homeowner.


Located in the City of Markham, Unionville is a beautiful and historic neighbourhood located in the Hwy. 7 and Kennedy Road area. Founded in 1784, Unionville is best known for its small-town vibe and the main street lined with shops in buildings dating back over a century.

Unionville City of Markham
Unionville in the City of Markham

In the north end of Unionville, Toogood Pond Park attracts not only hikers and nature lovers, but also a diverse number of animal species including ducks, geese, and turtles.

Squirrels are abundant in this area as they search for acorns, berries, and the occasional person handing out peanuts.

This case will illustrate how a squirrel breached a roof and made itself at home in the attic of a house in Markham.


We were informed by the property owner that their tenant on the second floor had been hearing activity noise coming from the attic for some time- a clear indicator that an animal had made its way into the house.

large hole found at the base of the chimney on the roof
The old repair did not hold up against the squirrels. The animals chewed through the repair and the plywood to gain entry into the attic.

A large hole was found at the base of the chimney on the roof.

Our team of qualified and certified wildlife technicians was dispatched to assess the situation and take the necessary actions to remove the squirrel or squirrels from the attic.

Upon inspecting the roof, we found a large hole at the edge of the chimney. It appeared the hole had been previously patched with a soft sheet of plastic (?). The squirrels had broken a section of the patch and were able to enter the attic.

A previous hole cover was found to be damaged and compromised.
A previous hole cover was found to be damaged and compromised.

Other points of potential entry were identified in the roof vents and plumbing vents. These are usually made of plastic and are often destroyed by animals seeking a warmer place. This is especially frequent during colder weather.


Our technician began by clearing out all the debris around the hole next to the chimney. A plastic sheet that had been patching a previous hole had been damaged along with a few roof shingles.

After clearing the area, we installed a one-way door to allow any squirrels in the attic to move out in a safe and humane way. Not doing so would trap the animals in the attic where they would eventually perish.

Because activity appeared to have been taking place in the primary entry point for some time, it was suggested that we disinfect and deodorize the area to kill any pathogens and remove all the scents that may attract other animals.

Plumbing vents and roof vents galvanized steel mesh.
Plumbing vents and roof vents were covered with galvanized steel mesh

Plumbing vents and roof vents were covered with galvanized steel mesh.

We then moved on to cover five roof vents and two plumbing vents with a commercial-grade galvanized steel mesh structure. This will prevent future animals from attempting to breach the attic through the vents.

roof protected with galvanized steel mesh
The roof hole was covered with flashing metal and protected with galvanized steel mesh.

The one-way-door was removed after a few weeks. This timeframe is critical as it gives the squirrels enough time to exit the attic. At that time, our technician sealed the whole with flashing metal and protected the area with galvanized steel mesh.


It is not unusual for squirrels to look for a warm place to nest, keep warm, and hide from predators such as hawks and foxes. The attic of a house is the ideal place as it is extremely confined. Once inside, squirrels may start to chew through electrical wiring and compress the insulation. This will cause the heat retention capacity of the insulation to decrease and make it less efficient.

In this case, we found that a previous solution to the problem had failed and the squirrels were able to enter the attic once again. When sealing roof holes, it is important to use a strong and durable material, such as metal, to prevent animals from gnawing their way back in.

Get a Free Quote