Overview An ice dam is an ice buildup on the eaves of sloped roofs in heated buildings, forming when melting snow refreezes at the roof’s edges. This ice formation prevents proper drainage of meltwater, causing water to back up under roofing materials, potentially leading to leaks, structural damage, and interior damage to walls, ceilings, insulation, and personal property. Ice dams are particularly common in regions with cold climates and heavy snowfall.
Formation Mechanism Ice dams form when accumulated snow on the roof melts due to heat escaping from the building’s interior. This meltwater flows downward until it reaches a part of the roof that remains below freezing – typically at the eaves, where there is no direct heating. The meltwater then refreezes, forming a growing ridge of ice that traps additional water behind it. The trapped water can seep under shingles, leading to water intrusion and subsequent damage inside the building.
Key factors contributing to ice dam formation include:
- Inadequate Roof Insulation: Heat escaping through an under-insulated attic or roof warms the surface and causes snow to melt.
- Poor Ventilation: Inadequate airflow in the attic or roof cavity allows heat to accumulate under the roof surface, increasing melting.
- Snow Accumulation: A thick layer of snow acts as an insulator, allowing heat from the house to warm the roof unevenly.
- Freezing Outdoor Temperatures: Ice dams commonly occur when the under-roof temperature is above freezing while the outdoor temperature remains below freezing (typically below 22°F or -6°C).
Effects of Ice Dams Unchecked ice dams can lead to severe consequences, including:
- Roof Damage: Ice dams add weight and stress to the roof structure, increasing the risk of structural damage and premature aging of roofing materials.
- Water Leaks: Meltwater can seep under shingles, causing leaks that damage ceilings, walls, insulation, and electrical wiring.
- Mold and Mildew Growth: Persistent moisture penetration can lead to mold growth, which poses health risks and requires costly remediation.
- Gutter and Fascia Damage: The weight of ice dams can damage gutters, downspouts, and fascia boards, potentially leading to expensive repairs.
- Personal Safety Risks: Large icicles and ice buildup pose hazards, potentially injuring people or damaging vehicles and property when they break off.
Mitigation and Prevention Strategies To prevent ice dams and their associated damage, several techniques can be employed:
1. Insulation Improvements:
- Increasing attic insulation minimizes heat loss, keeping the roof’s surface temperature lower and reducing the likelihood of snowmelt.
- Properly sealed attic floors prevent warm air from escaping into the roof space.
2. Roof Ventilation Enhancement:
- Installing ridge and soffit vents helps regulate attic temperature, keeping the roof cold enough to prevent uneven melting.
- Mechanical ventilation systems can supplement natural airflow if necessary.
3. Ice and Water Shield Installation:
- Applying a waterproof membrane beneath the roofing material (commonly required by building codes in cold regions) helps prevent water infiltration even if an ice dam forms.
4. Heat Tape or Heating Cables:
- Installing heat cables along eaves and in gutters creates pathways for meltwater to drain properly, reducing the risk of ice dam formation.
- However, heating cables consume energy, can damage roofing materials over time, and may pose fire hazards if improperly installed.
5. Roof Design Considerations:
- A steeper roof pitch allows snow to slide off more easily, reducing accumulation and subsequent melting.
- Metal roofing materials provide a slick surface that prevents ice dam formation.
- Installing an “ice belt,” a strip of metal roofing near the eaves, can help minimize ice buildup.
6. Snow Removal:
- Using a roof rake to remove snow after heavy snowfall can prevent excessive buildup, reducing the likelihood of melting and refreezing.
- Care must be taken to avoid damaging roofing materials while removing snow.
Ice Dam Removal Techniques If an ice dam has already formed, removal techniques include:
- Manual Removal:
- Using a roof rake or shovel to clear snow before ice builds up can prevent further accumulation.
- Chiseling or breaking ice manually is discouraged, as it can damage the roofing materials.
- Professional Steam Removal:
- Specialized contractors use low-pressure steamers to melt ice safely without harming the roof.
- Ice Melt Socks or Chemical Treatment:
- Permeable socks filled with ice melt (such as calcium chloride) can be placed on ice dams to help create drainage channels.
- Care must be taken to avoid using rock salt, which can damage shingles, metal components, and surrounding vegetation.
Preventing ice dams is essential for maintaining the integrity of a roof and preventing costly damage. A combination of proper insulation, effective ventilation, and proactive snow removal can significantly reduce the risk of ice dam formation. If an ice dam does occur, professional removal methods are recommended to prevent unintentional roof damage. Addressing these issues promptly can enhance a building’s longevity and reduce the risk of expensive repairs.
Source: Wiki Ice Dam