Ice Dams in New Jersey: Why They Form and How to Stop Them
Every January we get the same call. The roof is not the problem — the attic is.
By The Century Roofing Team — Roofing contractors, Carteret, New Jersey
Published January 14, 2026 · Reviewed January 14, 2026
How an ice dam forms
Snow sits on the roof. Heat escaping from the living space warms the decking under the middle of the slope, and the underside of that snow melts. The water runs down to the overhang, which is not warmed by the house because there is no living space beneath it, and refreezes.
Repeat that for a week and the ridge of ice at the eave grows tall enough to hold standing water behind it. Shingles shed running water; they do not hold back a pond. Water works up under the courses and into the house.
Watch out
What does not fix it
- Chipping the ice off with a hammer or hatchet — this damages shingles and gutters
- Salt tablets thrown into the gutter, which corrode metal and stain siding
- A new roof, if the attic conditions that caused it are unchanged
- Heat cable alone, which manages the symptom and adds an electric bill
What actually fixes it
- 1
Air sealing
Close the gaps where warm air enters the attic — top plates, recessed lights, chimney chases, and attic hatches.
- 2
Insulation depth
Bring insulation to a proper depth so ceiling heat stays in the ceiling.
- 3
Balanced ventilation
Intake at the soffit and exhaust at the ridge, so the attic runs close to outdoor temperature.
- 4
Ice-and-water membrane
At the eaves during the next roof replacement, protecting the deck when a dam does form.
Emergency measures during a dam
A roof rake used from the ground to pull snow off the lower few feet of the slope removes the fuel for the dam. That is the safest thing a homeowner can do mid-winter. If water is already entering, call us — we can steam a channel through the ice rather than break it apart.