Ice Dams: Why They Form and How to Prevent Them

Every New Jersey winter, ice dams damage roofs and cause leaks. Understanding how they form is the first step to preventing them.

What Is an Ice Dam?

An ice dam is a ridge of ice that forms at the edge of a roof and prevents melting snow from draining. The water backs up behind the dam and can work its way under the shingles and into your home.

Why Ice Dams Form

Ice dams form when heat escaping into the attic warms the roof deck and melts the snow on the upper roof. That meltwater runs down to the cold eaves — which are below freezing — and refreezes, building a dam over time.

How to Prevent Ice Dams

• Ensure proper attic insulation to keep heat out of the attic.
• Ensure balanced attic ventilation to keep the roof deck cold.
• Install ice-and-water shield along the eaves during roofing.
• Keep gutters clear so meltwater can drain.

The Long-Term Fix

The most reliable protection comes from a properly installed roof system with ice-and-water shield at the eaves and valleys, plus good attic ventilation and insulation. We build this into every roof we install.