Ice Dams in Connecticut: Causes, Prevention, and Fixes

How an ice dam forms

An ice dam is a plumbing problem caused by a thermal problem. Heat escaping from the living space warms the roof deck, melting the snow on the upper roof. That meltwater runs down to the eaves — which sit beyond the heated house and stay below freezing — and refreezes into a ridge of ice. More meltwater pools behind the ridge, and because shingles are designed to shed water downward, not to hold back standing water, it works its way under the shingles and into the house. The stain on the ceiling is the last symptom, not the first.

What actually prevents ice dams

• Ice-and-water shield. A self-sealing membrane under the shingles at the eaves and in valleys. On a replacement, it should extend from the eave up past the interior wall line — this is the last line of defense when a dam does form, and it's standard on a good Connecticut replacement.
• Attic air sealing. Warm air leaking through recessed lights, attic hatches, and plumbing chases is the heat source. Sealing those leaks does more than any gadget.
• Insulation and ventilation, together. Insulation slows heat loss; ventilation keeps the roof deck cold and carries moisture out. One without the other underperforms — a well-insulated attic with no ventilation still traps moisture, and ventilation over a leaky ceiling just vents your heat.
• Gutter and valley maintenance. Debris dams in gutters and valleys hold water in exactly the wrong places. Clean them in late fall, before the first freeze.

What to do about an active ice dam

First, protect the interior: move valuables, catch drips, and note where water enters — that tells the roofer where the dam is working. Outside, do not chip at the ice with a hammer or axe; you'll break shingles and create leaks worse than the dam. A roof rake can clear snow from the lower roof from the ground, and calcium chloride in a stocking laid across the dam can open a drainage channel — but both are stopgaps. The permanent fix is the system above, and the right time to install it is at replacement, when the roof is already open.

What not to buy

Heat cables have their place on specific problem roofs, but they treat the symptom, use electricity all winter, and fail at the worst times. If a contractor's whole ice-dam plan is cables, get a second opinion from someone who will talk about insulation, air sealing, and shield.

Planning a replacement? Request your free quote →