Quick Answer
Ice dams happen when heat escapes into the attic and warms the roof unevenly. Meltwater refreezes at the edge, forms a ridge of ice, and can force water back under shingles into the home.
What Is an Ice Dam?
An ice dam is a ridge of ice that forms near roof edges and gutters after snowmelt refreezes.
Once that ridge blocks drainage, meltwater can back up beneath roofing materials and leak into ceilings or walls.
What Causes Ice Dams
- Heat loss from the attic
- Uneven roof temperatures
- Inadequate attic insulation
- Poor attic ventilation
- Repeated thaw-freeze weather patterns
Common Warning Signs
- Large icicles at roof edges
- Ice ridges along gutters or eaves
- Water stains on ceilings
- Peeling paint near rooflines
- Damp insulation in the attic
How to Help Prevent Ice Dams
Improve Attic Insulation
Better insulation helps limit heat transfer from living spaces into the attic and keeps roof temperatures more consistent.
Improve Ventilation
Balanced intake and exhaust ventilation can reduce warm spots that accelerate uneven melting.
Air-Seal the Ceiling Plane
Seal attic bypasses around fixtures, duct penetrations, and top plates to reduce heat leakage.
Manage Roof Snow Safely
Use a roof rake from the ground when conditions are safe, and avoid climbing onto icy roofs.
What Not to Do
- Do not chip ice with sharp tools that can damage shingles
- Do not use rock salt that can corrode metal and harm landscaping
- Do not ignore interior leak stains during winter
When to Call a Professional
Call a professional if active leaks appear, heavy ice buildup continues, or attic insulation and ventilation need correction.
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