What Causes Ice Dams and How Do They Damage a Roof?

A warm attic is the primary cause of ice dams. Heat from your living space rises and warms the underside of the roof deck. This warmth melts snow on the roof's surface, even when the outside air temperature is below freezing. The resulting meltwater flows down toward the colder roof edges. Poor attic insulation and air leaks are common culprits for this heat loss.

With an ice dam blocking drainage, water pools behind it on the roof. This standing water finds its way under shingles, through nail holes, and past roofing felt. It can soak into the wooden roof deck and sheathing. Over time, this repeated soaking leads to wood rot and compromises the structural integrity of your roof. The water damage is often hidden from view until it becomes severe.

Prevention focuses on keeping your attic cold and the roof surface uniform in temperature. Proper insulation and ventilation work together to achieve this. Seal any gaps that allow warm air to leak from your living space into the attic. Keeping gutters clean helps prevent ice buildup in the gutters themselves. A roof rake can remove snow before it has a chance to melt and refreeze.

• Add more insulation to your attic floor to keep heat in.
• Seal air leaks around light fixtures, plumbing vents, and chimneys.
• Ensure your attic has adequate ventilation to keep it cold.
• Keep gutters and downspouts clear of leaves and debris.
• Use a roof rake to safely remove snow after a storm.
• Consider installing heated cables along the eaves for vulnerable roofs.