Ice Dam Roof Repair in Hackettstown, NJ

Why Hackettstown gets so many ice dams

Ice dams need three things: snow on the roof, a warm attic, and cold eaves. Warren County supplies plenty of the first - it's one of the snowiest parts of New Jersey. And a lot of Hackettstown homes supply the second, because they were built decades ago with little attic insulation and almost no ventilation.

Here's what happens: heat from the house rises into the attic and warms the roof boards. Snow on the upper part of the roof melts, even when the air outside is below freezing. The water runs down to the eaves, which hang out past the warm walls and stay cold, and it freezes there. Day after day, that ridge of ice grows. Eventually meltwater pools behind it with nowhere to go - and works its way up under the shingles and into the house.

Signs you have an ice dam

• A thick ridge of ice along the roof edge or in the gutters
• Large icicles, especially ones with water dripping from them on a sunny day
• Water stains on ceilings near outside walls, or at the top of walls
• Peeling paint or damp spots on walls below the eaves
• Snow melting on the upper roof while the lower edge stays frozen
• Frost or wet patches on the underside of the roof boards in the attic

What to do while it's happening

• Rake the snow off the lower three or four feet of the roof from the ground with a long-handled roof rake. Less snow means less meltwater feeding the dam.
• Don't chip, hammer or shovel the ice. You'll damage the shingles and gutters, and working on a ladder over ice is dangerous.
• Calcium chloride in a nylon stocking laid across the dam can melt a channel for water to drain. Avoid rock salt, which damages shingles, metal and plants.
• Catch water inside and photograph any damage.
• For a big dam, a roofer or snow-removal professional can clear it with low-pressure steam, which melts the ice without harming the roof.

Repairing the damage

Once the ice is gone, a roofer checks the eaves for water-damaged shingles, soaked underlayment and soft roof boards, and the gutters and fascia for damage from the weight of the ice. Shingles that were lifted by ice may need replacing, and any rotted boards along the edge get replaced before new shingles go on.

Preventing ice dams for good

Fixing the leak treats the symptom. Preventing ice dams means keeping the roof cold and evenly frozen:

1. Seal air leaks into the attic. Warm air escaping around attic hatches, recessed lights, plumbing stacks, chimneys and top-floor walls is the main driver.
2. Add insulation. Many older Hackettstown homes have far less than current recommendations.
3. Ventilate the attic. Cold air should come in at the soffits and leave at the ridge, keeping the roof boards near outside temperature. Make sure insulation isn't blocking the soffit vents.
4. Vent bathroom fans outdoors, not into the attic.
5. Ice and water shield. When the roof is replaced, a self-sealing waterproof membrane along the eaves and in the valleys stops water that does get under the shingles. It's standard practice on new roofs in this climate. See roof replacement.
6. Keep gutters clean before winter so meltwater can drain.

Heat cables along the roof edge can help in problem spots, but they treat the symptom rather than the cause and need to be installed carefully.

Metal roofs and ice

Metal roofs shed snow well, which reduces ice damming, but they can drop large slabs of snow and ice suddenly. Snow guards above doorways, walkways and driveways are a good idea. See metal roofing.

Plan ahead

The best time to deal with ice dams is the fall before. If your house had ice dams last winter, ask a roofer to look at the attic and eaves before the snow comes. Our post on getting your roof ready for a Warren County winter has a full checklist.