Ice dam at a Jamesville eave: what the thaw did, and what the edge needs

The weather station at Syracuse sees the temperature cross freezing on about 84 days each year. March is the worst month for it, about 17.8 crossings against 11.9 in January. Snow melts on the warmer part of a roof, runs to the cold overhang and freezes there into a dam. Water behind the dam is forced back under the shingles.

The same freeze-thaw pattern applies across Onondaga County, so the useful question is about your eave, not your hamlet. The eave is where to look first.

State code asks for an ice barrier along the lowest edge where ice has formed and backed water up under the roofing. It runs past the exterior wall line. It also asks for a drip edge at the eave. Ask the roofer to check for both and write down what is there.

Then ask what the water did. Look at the deck along the edge and at the ceiling below it. If the boards are sound, the fix can stay at the edge. If they are stained or soft, more deck comes out, and replacement becomes a fair question.

The federal energy guidance names air sealing, insulation and ventilation as the cause upstream. That work is separate from the roofing, and a roofer can tell you which part is which.