What Is an Ice Dam?
An ice dam is a ridge of frozen water that forms along a roof edge and blocks melting snow from draining. Water can collect behind the ridge and move beneath shingles or into roof and wall materials. Ice dams usually develop when roof heat melts snow above colder, unheated eaves.
Quick Facts About Ice Dam
Category
Roof drainage problem
Used for
Identifying frozen roof-edge buildup
Common confusion
Mistaken for harmless snow or frost
Also called
Ice Damming, Roof ice dam
Often discussed with
Roof Repair
Key Takeaways About Ice Dam
- Ice dams form at colder roof edges.
- Blocked meltwater can enter roof materials.
- An ice dam is not the same as ordinary roof ice.
How Ice Dam Works
An ice dam forms when roof heat melts snow on an upper roof area. Meltwater runs toward the eave, where colder air freezes it. The growing ridge blocks the normal drainage path.
Related glossary terms: Air Sealing, Flashing, Rafter.
Water held behind the ridge can move under shingles and reach roof sheathing. From there, moisture may stain ceilings, wet insulation, or damage wall materials. A roof repair inspection looks for the dam, damaged coverings, open seams, and moisture inside the roof assembly.
Roof flashing near valleys, walls, and edges can affect how far water travels. Attic insulation and air sealing also affect roof temperatures, so repairs may involve more than removing visible ice.
Expert Note
When we inspect an ice dam, we trace the water path from the roof edge into nearby materials. We check shingles, flashing, sheathing, insulation, and interior finishes for signs of moisture. Our roof repair plan addresses visible damage and the conditions that let water collect.
Ice Dam in Practice: A Real-World Example
A homeowner sees a thick frozen ridge along the lower roof edge after snow. During roof repair, the inspection finds lifted shingles and damp sheathing behind the ridge, so those areas need correction and drying.
Related Services
Related Terms
Air Sealing
Air Sealing is the process of closing unwanted gaps and cracks in a building enclosure. It…
Flashing
Flashing is a thin, shaped material that directs water away from roof joints, wall edges, chimneys…
Rafter
A rafter is a sloped structural member that supports a roof deck, shingles, insulation, and related…
R-Value
An R-Value is a measure of how strongly building insulation resists heat flow. Higher R-Values indicate…
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