What an ice dam actually is
An ice dam is a ridge of ice at the roof edge that blocks melt water from draining into gutters. Water backs up under shingles and can leak into walls, ceilings, and insulation.
In New Hampshire, dams often follow a freeze–thaw week: snow melts on warmer south-facing slopes, runs down, and refreezes on shaded north eaves overnight.
Common causes on NH homes
Most ice dam problems are heat-loss and ventilation problems, not bad luck:
- Warm air leaking from living space into the attic
- Blocked or short soffit vents
- Inadequate ice & water shield at eaves and valleys
- Gutters frozen full, forcing water over the edge
- Complex roof geometry with long north-facing eaves
What to do when you see water stains
Document photos of the ceiling stain, the exterior ice buildup, and any active dripping. Do not climb on an icy roof.
Call for a careful interior and exterior look. A written scope should name ice protection, ventilation improvements, and flashing — not just "patch the leak."
Prevention that lasts
On a roof replacement, ice & water membrane at eaves and valleys is standard on our scopes for New Hampshire — not an upsell surprise on tear-off day.
Pair that with balanced attic ventilation and sealing air leaks at penetrations. Siding and window projects are a good time to address wrap and flashing transitions too.