The answer to 'underlayment ice dams' is that ice dams are a common roofing problem caused by poor attic insulation and ventilation. Ice dams form when heat escapes the home, melting snow on the roof. The melted water then refreezes at the roof's edge, creating a dam that prevents proper drainage and can lead to water damage.
Symptoms of ice dams include icicles forming along the roof's edge, water stains on the ceiling, and pooling water in the gutters. Solutions include improving attic insulation, adding roof vents, and installing a water-resistant underlayment beneath the shingles. In severe cases, you may need to call a professional roofer to properly address the issue.