Ice dams and ceiling stains in Baldwinsville, NY: start at the edge of the roof

Snow that sits on a warm roof melts from below, runs to the cold overhang and refreezes there. The Department of Energy describes that mechanism, and state code answers it with an ice barrier at the eave where ice has formed and backed water up under the roofing.

The station that counts freeze and thaw crossings for the north county is at Brewerton. It logs about 109 crossing days a year. Read that as background for the area, not your street's count, and as a reason the eave cycles more than the field of the roof.

The practical question is what is under your lowest shingles. An older roof may have only plain underlayment at the edge. Ask the roofer to look, and to write what they see.

Ask yourself when the stain appears. One that comes in a thaw and dries in warm weather fits water backing up at the edge. One that comes with every rain points elsewhere, and the roofer should hear which you have, with dates if you can.

Ask the roofer for two prices side by side: rebuilding the eave, and replacing the whole roof. Dark or soft boards at the edge go in the eave price. If the slopes above are sound, the smaller job may be enough, and if many boards are soft, the larger job is the honest answer.

If water drips in, clear the floor under the stain and photograph the ceiling first, so the roofer sees it undisturbed.

The Department of Energy puts the upstream cause in warm air reaching the deck, a job separate from the roofing. A roofer who sees signs of it can say so. Name the room and the month in the form.

Where ice forms at the eaves, the code wants a barrier that starts at the lowest edge and runs 24 inches or more past the wall line, built from cemented double underlayment or a self-adhering sheet. Ask the roofer to put the distance in writing for your house, and where the barrier ends on the slope.

Ask whether the drip edge is new and whether old rows come off only at the eave or across the whole slope. Then ask how the new courses join the old; a roofer used to this work answers each in a sentence.

Finally, ask the village code office whether eave work needs a permit. The office takes calls from 8 a.m. to noon on weekdays, and the village names roofs among work that must meet code.

No new eave detail stops a dam forming on a roof that leaks heat. Its job is to protect the deck, so doubt anyone who promises more.

From the ground, look at the edge on the next cold morning after a thaw. A band of ice along the lowest row, with bare shingles above, is the dam. Photograph it and note which sides of the house show it.