Every winter, homeowners across New Hampshire deal with ice dams — those thick ridges of ice that form at the edge of your roof and prevent melting snow from draining. When water backs up behind the dam, it can seep under shingles and into your home, causing significant damage to walls, ceilings, insulation, and more.
What Causes Ice Dams?
Ice dams form when heat escaping from your living space warms the roof deck unevenly. Snow melts on the warmer upper portions of the roof, flows down, and refreezes at the colder eaves where the roof extends past the exterior walls. Over time, this creates a dam of ice that traps water behind it.
The Three Key Factors
Heat loss: Poor insulation allows warm air to reach the roof deck. Ventilation: Inadequate attic ventilation traps warm air instead of flushing it out. Snow cover: A heavy snow load acts as insulation, keeping the roof surface warm enough to melt.
Prevention Strategies
Improve attic insulation: Bring your attic insulation up to R-49 or higher (the recommended level for New Hampshire). This keeps heat in your living space where it belongs.
Seal air leaks: Recessed lights, attic hatches, plumbing vents, and electrical penetrations are common pathways for warm air. Sealing these can dramatically reduce heat loss.
Ensure proper ventilation: A balanced system of soffit vents and ridge vents keeps the roof deck cold and uniform, preventing the temperature differential that causes melting.
Install ice and water shield: During your next roof replacement, have ice and water shield membrane installed along the eaves — at minimum 3 feet past the exterior wall line.
When to Call a Professional
If you're already seeing ice dams forming, don't try to hack at them with a hammer or use rock salt — both can damage your roof. Professional ice dam removal uses low-pressure steam to safely clear the ice without harming your shingles. At Apex Exteriors, we handle both emergency removal and long-term prevention solutions.
