Average annual snowfall in the Syracuse region
Ice dams are the top winter roof leak cause
Of ice dams trace to poor attic ventilation
Freeze-thaw cycles hit Upstate NY each winter
Ice dams are the leading cause of winter roof damage across Central and Upstate New York. Understanding how they form,
why they cause leaks, and what you can do to prevent them is essential for protecting your home through the long, harsh
winters that define our region. Here’s how the process works — step by step.
The Root Cause Warm air from your living spaces rises into the attic. If insulation is inadequate or ventilation is poor, that heat transfers through the roof deck — warming the shingles and snow sitting on the upper sections of your roof while the eaves remain cold.
The Melt Begins The escaping heat melts snow on the warmer upper and middle portions of the roof. This meltwater flows down the roof surface beneath the remaining snow layer — invisible from the ground but actively moving toward the colder eave edges.
The Dam Builds When the flowing meltwater reaches the unheated overhang at the roof's edge, it refreezes into a ridge of solid ice. Each freeze-thaw cycle adds another layer. Over days and weeks, this ice ridge grows into a thick dam that blocks all drainage.
The Leak Begins With the ice dam blocking drainage, meltwater pools behind the dam and has nowhere to go. Shingles are designed to shed water flowing downward — not hold standing water. The pooled water seeps under shingles, over flashing, and into your roof system.
Interior Consequences Once past the shingles, water saturates the underlayment and decking, then drips into the attic — staining ceilings, soaking insulation, promoting mold growth, and damaging walls and electrical systems. The damage often spreads far from the original entry point.
