The answer to 'roof decking ice dams' is that ice dams form when snow on the roof melts, usually due to heat escaping from the home, and then refreezes at the roof's edge. This can cause water to back up under the shingles and leak into the home, potentially damaging the roof decking. Common causes include poor attic insulation, inadequate ventilation, and air leaks in the home's envelope.
Symptoms of roof decking ice dams include visible icicles along the roof's edge, water stains on ceilings or walls, and peeling paint or wallpaper. Solutions can include improving attic insulation, sealing air leaks, and ensuring proper roof ventilation. In some cases, a professional roofer may need to remove the ice dam and repair any resulting damage to the roof decking.