Ice dams on Rhode Island homes

How an ice dam forms

Heat from the house leaks into the attic and warms the roof deck. Snow on the upper roof melts even on a freezing day, and the water runs down to the eaves. The eaves hang out past the warm walls, so they stay cold, and the water freezes there. The ridge of ice grows with each thaw, and the next meltwater backs up behind it and works under the shingles.

Southern New England winters are made for this: a snowstorm, then a run of days that swing above and below freezing. Inland towns such as Cumberland, Coventry and Woonsocket usually hold snow longer than the coast, but a nor'easter can leave enough on any Rhode Island roof.

Which houses get them

• Capes with finished second floors. Knee walls and sloped ceilings leave little room for insulation or air flow.
• Triple-deckers. The top-floor apartment sits right under a shallow roof, often with little insulation. See triple-decker roofs.
• Older colonials and Victorians in Providence, Pawtucket and Bristol, with board decking, complicated rooflines and valleys where snow piles up.
• Any house with recessed lights, attic ductwork or a leaky attic hatch, all of which pour warm air into the attic.

What a new roof should include

1. Ice barrier membrane at the eaves. A self-adhering underlayment bonded to the deck, from the roof edge to at least 24 inches inside the line of the outside wall, and in the valleys.
2. Drip edge on every edge, lapped with the membrane the way the manufacturer specifies.
3. Balanced ventilation. Open soffit vents at the bottom and a continuous ridge vent at the top, with baffles so insulation does not block the air path.
4. Bath and kitchen fans ducted outdoors, never into the attic.

The asphalt shingle roofs page walks through the full layer order of a shingle replacement.

Replacing a roof in winter

Roofs are replaced in Rhode Island winters. Shingle seal strips need warmth to bond, so cold-weather jobs often include hand-sealing, and crews lose days to snow and ice. If the roof is leaking now, a careful winter job usually beats waiting for spring. Ask how the crew protects the house if weather turns while the old roof is off, and check the roofer's registration first in checking a roofer.