Roofing
Ice Dams in New Hampshire: What Causes Them & How to Stop Them
Short answer: An ice dam is a ridge of ice that forms at the edge of your roof and stops melting snow from draining. The trapped water backs up under your shingles and leaks into the house. They’re caused by uneven roof temperatures — a warm upper roof melts snow, which refreezes at the cold eaves. The fixes are better attic insulation and ventilation, and a proper ice-and-water barrier at the roof edge.
Why ice dams happen
In a New Hampshire winter the cycle looks like this:
- Heat escaping from your living space warms the upper part of the roof.
- Snow there melts and runs down toward the cold eaves and gutters.
- At the edge, where there’s no warmth from below, the water refreezes into a dam.
- More meltwater pools behind the dam, works under the shingles, and leaks inside.
The root cause is almost always heat escaping into the attic plus poor ventilation — not the roof surface itself.
How to prevent ice dams
- Seal and insulate the attic floor so heat doesn’t reach the roof deck
- Ventilate the attic (balanced soffit intake + ridge exhaust) to keep the roof cold and even
- Ice-and-water shield along the eaves and valleys — a waterproof membrane under the shingles that stops backed-up water from getting in
- Keep gutters clear so meltwater can drain
- Sized, well-pitched gutters and good soffit & fascia ventilation help too
These are exactly the details we build into every roof replacement — they’re what separates a roof that survives New England winters from one that leaks.
Already seeing leaks or ice buildup?
Don’t ignore it — trapped water rots the roof deck and grows mold in the attic. Get the roof and attic inspected to find the real source. Belgres handles roof repair and ice-dam damage across Greater Nashua, NH.
Request a free inspection or call us — we’ll find the problem and fix it right.