The short version
- Ice dams form when attic heat melts snow that refreezes at the cold roof edge.
- Don't chip at the ice. Rake snow from the ground and call a pro if water gets in.
- Air sealing, insulation and ventilation prevent them long term.
- Ohio's residential code calls for an ice barrier at the eaves, including when a roof is replaced.
What an ice dam is
An ice dam is a ridge of ice that forms along the edge of the roof. Snow higher up melts, the water runs down to the colder roof edge, and it refreezes there. As the ridge grows, meltwater pools behind it and can back up under the shingles and into the house.
Central Ohio's winters are made for this. In February 2026, ABC6 reported on local roofers seeing a jump in calls as repeated melting and refreezing built thick ice along rooflines, and noted that water backing up behind the ice can seep under shingles and cause leaks and interior damage.
Why they form
The root cause is usually heat escaping into the attic. A warm attic warms the roof deck and melts the snow from below, while the overhang at the eaves stays cold. Common culprits:
- Gaps around attic hatches, light fixtures, plumbing and chimneys that leak warm air
- Thin or uneven attic insulation
- Poor attic ventilation
- Clogged gutters that hold ice and water at the roof edge
Warning signs
- Large icicles or thick ice along the gutters
- Water stains on ceilings or walls near outside walls during or after snow
- Damp insulation or frost on the underside of the roof deck in the attic
Ice dam removal: what to do (and not do)
- Don't climb up or chip at the ice. It's dangerous and easily damages shingles and gutters.
- From the ground, a roof rake can pull snow off the lower few feet of the roof so less water feeds the dam.
- If water is coming inside, catch it, take photos and call a roofer. Angi's Columbus data puts professional ice dam removal at roughly $500 to $700.
How to prevent them
- Air seal the attic floor so warm air stays in the house.
- Add insulation where it's thin.
- Ventilate the attic so the roof deck stays cold, with intake at the eaves and exhaust at the ridge.
- Clean gutters before winter.
- Use ice barrier (often called ice and water shield) when you re-roof. The Residential Code of Ohio calls for an ice barrier from the roof edge to at least 24 inches inside the exterior wall line. It's a waterproof membrane under the shingles that stops backed-up water from getting in. Every roof we install includes it.
Heat cables along the roof edge can help in problem spots, but they treat the symptom rather than the cause.