Gutters, Flashing & Ice Dam Control: what to know
Ice dams form when the upper part of a roof is above freezing and the eaves are below it. Heat escaping from the living space melts snow on the heated section; the meltwater runs down to the cold overhang, which has no heated space beneath it, and refreezes. The ridge of ice grows, water ponds behind it, and that standing water works under the shingle courses. Shingles shed water; they do not hold back a pond.
Why Connecticut gets them badly
Heavy snow that sits rather than sliding, long stretches where daytime temperatures hover around freezing while nights drop well below, and an old housing stock full of knee-wall attics, plaster ceilings with no air barrier, recessed lights punched through the ceiling plane and bathroom fans vented into the attic.
Removal
Low-pressure steam is the method that melts a channel through the dam without damaging the roof covering. Pressure washers, hammers, chisels, salt socks and blowtorches all cause damage that does not show until spring. Ask specifically for steam.
Prevention, in the order that works
- Air sealing. Seal the leaks between heated space and attic: top plates, chimney chases, wiring and plumbing penetrations, the attic hatch. Warm air leaking through gaps carries far more heat up than conduction through insulation.
- Insulation. Even, adequate depth across the whole ceiling plane, including over the exterior wall top plates where it is usually thin.
- Ventilation. Balanced soffit-to-ridge airflow to keep the deck cold.
- Ice and water membrane at the eaves as a backstop, installed at the next re-roof.
Gutters
Gutters do not cause ice dams, but blocked or undersized gutters make everything downstream worse, including foundation water, since a downspout discharging at the wall is one of the most common causes of a wet Connecticut basement. Clean them, size them for the roof area, and get the discharge four to six feet away from the building.