Ice damming occurs when snow on a roof melts, usually due to heat escaping from the attic or an unevenly heated roof and then refreezes at the eaves (the edges of the roof). This creates a "dam" of ice that prevents additional melting snow from properly draining off the roof. Instead, the water pools behind the ice dam and can seep under shingles, potentially causing roof leaks, water damage, and even structural problems. Here's a breakdown of the process:
Snow Accumulation: Snow builds up on the roof during a winter storm.
Melting: Warm air inside the attic or heat from the sun causes the snow to melt at the higher, warmer parts of the roof.
Refreezing: As the melted snow flows down the roof, it reaches the colder eaves or edges of the roof where it refreezes, forming an ice dam.
Water Pooling: The ice dam blocks further melted snow from draining, causing water to pool behind it.
Leakage: Over time, this pooled water can work its way under the shingles, potentially penetrating the roofing underlayment and causing leaks inside the home.
Potential Consequences of Ice Damming
Roof Damage: Water infiltration can rot roof decking and compromise the roof structure.
Gutter Damage: Ice dams can weigh down and damage gutters.
Interior Water Damage: Water may seep into walls, ceilings, and insulation, leading to stains, mold, and structural issues.
Preventing Ice Damming
Proper Insulation: Ensure the attic is well-insulated to keep heat from escaping and warming the roof.
Ventilation: Adequate attic ventilation helps maintain a consistent roof temperature.
Snow Removal: Safely remove snow from the roof using tools like a roof rake to minimize melting and refreezing.
Ice and Water Shield: Install an ice and water shield membrane under the shingles, especially at the roof edges.
Heating Cables: Use electric heating cables along the eaves to prevent ice from forming.
Addressing ice damming early can help protect the roof and avoid costly repairs.