Typical signs
- Repeated large icicles at the eaves.
- Frost on the underside of the roof, wet insulation or stains near soffits.
- Leaks during thaw or damp ceilings in winter.
Where it is often found
- Roofs in cold climates, especially at eaves, valleys and penetrations.
What it can mean
- Air leakage from the home into the attic.
- Insufficient ventilation or poorly distributed insulation.
What to check next
- Observe how snow melts on the roof.
- Look for frost, stains and compressed insulation areas.
- Check hatches, light fixtures, fan ducts and other air leaks.
Reasonable immediate actions
- Carefully clear accessible drainage paths; do not aggressively chop ice.
When to stop and call a professional
- Heavy snow load, major active leakage, falling-ice hazard or need for a complex enclosure correction.
Prevention
- Air sealing, continuous insulation, attic ventilation and indoor humidity control.