The answer to 'roof decking ice dams' is that ice dams form when melting snow refreezes at the edge of the roof, causing water to back up under the shingles and into the home. This is commonly caused by poor insulation or ventilation in the attic, which allows heat to escape and melt the snow on the roof. Symptoms include icicles, water stains on the ceiling, and damage to the roof and interior walls.
The best solution is to address the root cause by improving insulation and ventilation in the attic. This may involve adding more insulation, sealing air leaks, or installing a roof ventilation system. Homeowners can try temporary fixes like removing snow from the roof or installing heating cables, but these are only short-term solutions. For more complex issues, it's best to call a professional roofing contractor who can properly diagnose and resolve the problem.