If you've lived through a New Hampshire winter, you've probably seen ice dams — those thick ridges of ice that form along the eaves of roofs. They might look like a normal part of winter, but they're actually a serious threat to your home.
What Causes Ice Dams?
Ice dams form through a simple but destructive cycle:
- . Heat escapes through your roof from the living space below, warming the upper sections of the roof.
- . Snow melts on the warmed upper roof and flows down as water.
- . Water reaches the cold eaves (which aren't above heated space) and refreezes into ice.
- . The ice builds up into a dam that traps more meltwater behind it.
- . Trapped water seeps under shingles and into your home, causing interior damage.
The root cause is almost always inadequate attic insulation and ventilation. When warm air leaks into your attic, it heats the roof unevenly — creating the temperature differential that drives the whole cycle.
Prevention: The Long-Term Fix
The best approach to ice dams is preventing them from forming in the first place:
Improve attic insulation — The goal is to keep heat in your living space and out of the attic. Most older NH homes are under-insulated by modern standards. Adding insulation to R-49 or higher (the current code recommendation for our climate zone) can make a dramatic difference.
Improve attic ventilation — Proper soffit-to-ridge ventilation keeps the attic cold and the roof surface temperature even. Make sure soffit vents aren't blocked by insulation and that baffles are installed to maintain airflow.
Seal air leaks — Gaps around light fixtures, plumbing stacks, attic hatches, and recessed lights allow warm air into the attic. Sealing these is often the most cost-effective prevention measure.
Ice and water shield — During a roof replacement, we install ice and water shield membrane along the eaves and in valleys. This waterproof barrier is your last line of defense if ice dams do form.
Removal: When Prevention Isn't Enough
If you already have ice dams, here's what to do — and what NOT to do:
DON'T hack at ice dams with picks, axes, or hammers. You'll damage your shingles and possibly your roof structure.
DON'T use rock salt or calcium chloride directly on shingles. It can stain your roof and accelerate shingle deterioration.
DO call a professional who uses steam removal. Steam melts the ice quickly and safely without damaging your roof. This is the method we use at Archer Roofing.
DO address the interior water damage promptly. Mold can begin growing within 48 hours of water intrusion.
The Bottom Line
Ice dams are a symptom of a bigger issue — heat loss through your roof. While emergency removal is sometimes necessary, the real solution is addressing insulation, ventilation, and air sealing. During your free inspection, we'll assess your roof's vulnerability to ice dams and recommend the most cost-effective improvements for your specific situation.