What causes ice dams?

Heat escaping from the living space warms the roof deck and melts the snow on it. The meltwater runs down to the colder eaves, which hang out past the warm walls, and refreezes there. As that ridge of ice grows, water pools behind it and can back up under the shingles and into the ceilings and walls.

Are icicles a sign of an ice dam?

Large icicles along the eaves are a common warning sign, because they form from the same melt-and-refreeze cycle. Other signs are thick ice on the edge of the roof, water stains on ceilings near exterior walls, and damp insulation in the attic after a snowy stretch.

Should I chip ice dams off my roof?

No. Chipping with a hammer, shovel or ice pick easily breaks shingles and can tear gutters loose, and working on an icy roof is dangerous. Rake snow from the ground with a roof rake, and call a roofer if water is getting inside.

Does a new roof stop ice dams?

A new roof with ice and water barrier along the eaves and proper ventilation helps protect your home when ice dams form. But the root cause is usually heat loss into the attic, so insulation and air sealing matter just as much.

The Best Tips for Preventing Roof Ice Dams

By the Allabaugh Construction team · April 8, 2024 · Updated September 25, 2026

Winter in Northeast Pennsylvania and New Jersey brings snow, cold snaps and, for a lot of homes, ice dams. NEPA towns like Scranton and Wilkes-Barre typically see more snow and longer cold stretches than the Trenton area, but central New Jersey gets its share of snowstorms and freeze-thaw swings too, and those cycles are exactly what builds ice dams.

Ice dams start with uneven heat loss. Warm air leaking into the attic heats the roof deck and melts the snow on top of it. That meltwater runs down to the cold eaves and refreezes, building a ridge of ice. The ice blocks later meltwater from draining, so water pools behind it, works its way under the shingles and leaks into walls, ceilings and insulation.

The good news: ice dams are preventable. Here's how.

Improve Attic Insulation

Heat escaping from the house is the main cause of ice dams. Adequate attic insulation keeps that heat in the living space, so the roof deck stays cold and snow doesn't melt unevenly. Many older homes in our area, from Cape Cods in Mercer County to older two-story homes in the Wyoming Valley, have less attic insulation than today's standards call for. If you can see the tops of your ceiling joists, it's usually worth talking to an insulation contractor.

Seal Attic Air Leaks

Insulation works best when air leaks are sealed first. Check for gaps around bath fans, recessed lights, plumbing stacks, chimneys and the attic hatch. Sealing these with the right caulk, foam or weatherstripping keeps warm, moist air out of the attic. Around chimneys and flues, use only materials rated for that use.

Ventilate Your Roof

Balanced roof ventilation, with intake at the soffits and exhaust at or near the ridge, pulls cold outside air through the attic. That keeps the underside of the roof deck close to the outdoor temperature, so snow melts from the sun, not from house heat. Blocked soffit vents are a common problem, especially where insulation has been pushed into the eaves.

Keep Gutters and Downspouts Clear

Gutters packed with leaves hold water, and that water freezes and makes ice buildup at the roof edge worse. Clean them after the leaves drop in late fall, and make sure downspouts carry water well away from the house. Our gutter cleaning crews can handle that before winter.

Rake Excess Snow

After a heavy storm, use a long-handled roof rake from the ground to pull the first few feet of snow off the roof edge. Less snow near the eaves means less meltwater to refreeze. Don't climb on a snowy roof, and keep clear of power lines.

Make Sure There's Ice and Water Barrier at the Eaves

Ice and water barrier is a self-adhering membrane installed under the shingles along the eaves and in valleys. It won't prevent an ice dam, but it helps keep water that backs up from getting into the house. The International Residential Code, which both New Jersey and Pennsylvania build their residential codes on, calls for it at the eaves in areas where ice dams are a known problem. If your roof is due for replacement, confirm it's in the scope.

Consider Heat Cables for Problem Spots

Heat cables, installed in a zig-zag along the roof edge and in gutters, can melt channels so water drains. They're not foolproof and they use electricity, so think of them as a fix for a known trouble spot, not a substitute for insulation and ventilation.

Fix Roof Damage Before Winter

An aging or damaged roof is more likely to leak when an ice dam forms. Missing shingles, lifted flashing and worn seals give water an easy way in. A fall inspection and a timely roof repair are cheap insurance.

Use Ice Melt Carefully

Some ice-melt products can damage shingles, gutters and plants below. Avoid rock salt on the roof, and never chip at ice with a hammer or shovel. Focus on prevention instead.

Keep an Eye on Your Roof

Watch the roof through the winter, especially after snowstorms and freezing rain. Large icicles, thick ice along the eaves and water stains on ceilings near outside walls are warning signs. Address them quickly.

Stay Ahead of Ice Dams With Allabaugh

Preventing ice dams protects your home's structure and your peace of mind all winter. We install and correct roof ventilation, replace roofs with ice and water barrier at the eaves, and offer roof inspection and maintenance across Luzerne County, Lackawanna County and Mercer County, NJ.

Call our PA office at (814) 330-4897 or our NJ office at (609) 477-0487, or request a free estimate.