ICE DAM
PREVENTION
ONTARIO

Why ice dams are a serious Ontario roofing problem.

Ice dams form when snow melts higher on the roof and refreezes near the colder roof edge. Over time, this creates a ridge of ice that traps water behind it. That trapped water can work its way under shingles, into roof decking, behind walls, and into attic insulation.

In Ontario, ice dams are especially common because winter weather creates repeated melting and refreezing cycles. A roof may look fine from the ground while water is already moving beneath shingles or into vulnerable roof areas.

What Causes Ice Dams?

Ice dams usually form because of a combination of snow, roof temperature imbalance, attic heat loss, and poor ventilation. When warm air escapes into the attic, it heats the underside of the roof deck. Snow melts on the warmer roof surface, runs downward, then freezes again at the cold roof edge.

• Warm attic air melts snow from underneath
• Cold roof edges refreeze the meltwater
• Ice builds up along eaves and gutters
• Water becomes trapped behind the ice dam
• Leaks can develop under shingles and flashing

Warning Signs of Ice Dam Problems

Ontario homeowners should watch for visible and interior warning signs during winter and early spring.

How Ice Dams Damage Asphalt Roofs

Asphalt shingles depend on layered water shedding. Once ice traps water and pushes it backward under the roof surface, the system becomes vulnerable. Repeated freeze-thaw cycles can lift shingles, crack seal strips, weaken flashing areas, and expose roof decking to moisture.

Over time, ice dam damage can lead to mold, insulation problems, wood rot, drywall stains, and expensive repairs.

Why Metal Roofing Helps in Ontario Winters

Permanent interlocking metal roofing systems are designed to perform better in harsh winter conditions. Smooth metal surfaces shed snow more effectively than rough asphalt shingles, and properly installed interlocking systems provide stronger protection against wind, snow, and water intrusion.

• Improved snow-shedding performance
• Stronger resistance to freeze-thaw damage
• Reduced shingle lifting and cracking issues
• Long-term winter durability
• Better compatibility with proper ventilation strategy

Ice Dam Prevention Starts With the Whole Roof System

Preventing ice dams is not only about the roof surface. A complete approach includes ventilation, insulation, attic airflow, roof design, and durable exterior materials. ROOFNOW™ helps Ontario homeowners upgrade from short-term asphalt replacement cycles to permanent roofing systems built for Canadian conditions.