What Is an Ice Dam?
An ice dam is a buildup of ice that forms along the eaves of sloped roofs on heated buildings. It occurs when melting snow, caused by heat escaping from the roof, reaches the eaves where the temperature is lower, refreezing into a solid block of ice. This accumulation impedes proper drainage, leading to water backup that may seep through the roofing material, causing leaks and structural damage.
How Ice Dams Form
Ice dams are most common in regions with cold winters and heavy snowfall. They form when three key conditions are met:
- Subfreezing temperatures (usually below 22°F / -6°C)
- A thick layer of insulating snow on the roof
- Escaping heat from the building warming the roof surface
The mechanism behind ice dam formation works like this:
- Snow accumulates on the roof, forming an insulating layer.
- Heat from the attic or living space escapes through the roof, warming the lower layer of the snowpack.
- The melted snow flows downward until it reaches the eaves, where there is no interior heat to keep it from refreezing.
- As the water freezes at the eaves, an ice barrier forms, trapping additional meltwater behind it.
- With no way to drain properly, the backed-up water may seep under the shingles, leading to leaks, mold growth, and structural damage.
Effects of Ice Dams
The consequences of ice dams can be severe, including:
- Roof leaks – Water trapped behind an ice dam can seep under shingles, damaging the underlying structure.
- Interior damage – Water leaks may cause stained ceilings, peeling paint, and mold growth.
- Structural weakening – Repeated exposure to moisture can weaken the roof decking and insulation.
- Gutter and fascia damage – Heavy ice buildup can pull gutters away from the roof or break them completely.
- Personal injury risk – Large icicles or ice chunks falling from the eaves can pose a danger to people below.
Get Your Free Estimate Today
How to Prevent Ice Dams
Preventing ice dams requires addressing the root causes: insufficient insulation, poor ventilation, and heat loss. The following methods can help:
1. Improve Roof Insulation
- Proper attic insulation keeps heat from escaping through the roof.
- Insulate attic floors and seal air leaks to maintain a consistent temperature.
- Use R-38 to R-49 insulation in colder climates to prevent excessive heat loss.
2. Enhance Roof Ventilation
- Adequate ventilation ensures that warm air does not accumulate in the attic.
- Ridge and soffit vents allow cold air to circulate, keeping the roof temperature stable.
- Ensure at least one square foot of ventilation per 300 square feet of attic space.
3. Seal Air Leaks
- Close gaps around chimneys, plumbing vents, and electrical wiring.
- Use caulk or spray foam insulation to seal air leaks in the attic.
4. Install Ice and Water Shields
- Roofing membranes installed beneath shingles provide a waterproof barrier.
- Ice and water shields prevent leaks even if water seeps under the shingles.
5. Use Heat Cables
- Self-regulating heat cables can be installed along the eaves to create drainage channels.
- Heat cables should be installed properly to avoid fire hazards and excessive energy use.
6. Keep the Roof Clear of Snow
- Regularly remove snow from the roof with a roof rake.
- Clearing at least three to four feet of snow from the roof’s edge reduces ice dam formation.
7. Install Metal Roofing or Ice Belts
- Metal roofing allows snow to slide off easily, preventing ice buildup.
- Ice belts, a strip of metal roofing installed at the eaves, reduce water penetration.
How to Remove Ice Dams
If an ice dam has already formed, consider these removal methods:
1. Use a Roof Rake
- A roof rake with an extended handle allows for safe snow removal from the ground.
- Avoid chipping away at the ice, as this can damage shingles.
2. Create Drainage Channels
- Use calcium chloride ice melt in fabric socks and place them perpendicular to the ice dam.
- This helps create small channels for water to escape.
3. Hire Professional Steam Removal
- Steam machines can safely melt ice without damaging the roof.
- Avoid using blowtorches, hammers, or chisels, which can cause further damage.
4. Temporary Measures
- If a leak has started, place buckets or towels to catch water indoors.
- Use fans or dehumidifiers to dry affected areas.
Leak Prevention and Long-Term Solutions
To minimize long-term damage from ice dams, consider:
- Installing a roofing membrane under shingles to protect against water infiltration.
- Replacing asphalt shingles with metal roofing, which naturally prevents ice dams.
- Upgrading attic insulation and ventilation to eliminate conditions favorable for ice dams.
Get Your Free Estimate Today
Final Thoughts
Ice dams can be a serious problem, leading to costly repairs if not managed properly. The best approach is prevention through proper insulation, ventilation, and roof maintenance. However, if an ice dam does form, safe removal techniques such as steaming or calcium chloride application can help prevent damage. Regular roof maintenance and winter preparedness are key to ensuring your home remains protected during the colder months.