Ice dams are ridges of ice that form at the edge of a roof and prevent melting snow from draining off properly. They typically occur in cold climates during the winter when snow accumulates on a roof and begins to melt due to heat escaping from the house. The meltwater flows down the roof but refreezes when it reaches the colder eaves (the edges of the roof), creating a dam of ice. This dam can cause water to back up under the shingles and potentially leak into the home, leading to water damage, mold growth, and structural issues.
How Ice Dams Form
Ice dams can cause serious damage to your home if left unchecked, but understanding how they develop is the first step in preventing them. Here’s a closer look at the process behind their formation.
- Snow accumulates on the roof.
- Heat from inside the house warms the roof, causing the snow to melt.
- The meltwater flows down to the colder roof edges.
- When the water reaches the cold eaves, it refreezes, forming a barrier of ice.
- Additional meltwater pools behind the ice dam and can seep under shingles and into the building.
Common Causes of Ice Dams
Poor Attic Insulation
Poor attic insulation is one of the primary reasons ice dams form. When insulation is insufficient or uneven, heat from the living spaces below escapes into the attic and warms the roof deck. This localized warming causes the snow on the upper parts of the roof to melt, even while the edges remain cold. The meltwater then flows down to the colder eaves and refreezes, creating ice dams. Proper insulation helps keep the attic and roof cold, preventing this uneven melting.
Inadequate Ventilation
Inadequate ventilation in the attic can also contribute significantly to ice dam formation. Without proper airflow, warm air becomes trapped in the attic space, raising the temperature of the roof deck. This trapped heat causes snow to melt prematurely on the warmer sections of the roof. Good ventilation allows cold air to circulate under the roof, maintaining a more consistent temperature and reducing the chances of snow melting unevenly and refreezing at the edges.
Partially Melted Snow
Large temperature differences between the roof peak and eaves create ideal conditions for ice dams. The roof peak, which is often warmer due to heat loss from the home, causes snow to melt and run down toward the cooler eaves. Because the eaves are exposed and not warmed by the house, the meltwater refreezes there, forming a dam. This temperature gradient is often worsened by poor insulation and ventilation, but even in well-maintained homes, extreme outdoor temperatures can sometimes lead to this problem.
How to Prevent Ice Dams
Keep Your Roof Cold
Improve attic insulation and ventilation to keep the roof cold. Enhancing the insulation in your attic helps prevent heat from escaping through the roof, which is the main cause of snow melting unevenly. When combined with proper ventilation, cold air can circulate freely, maintaining a consistent roof temperature and reducing the risk of ice dams. Together, these measures create a barrier that keeps the roof surface cold enough to prevent snow from melting and refreezing at the eaves.
Use a Snow Rake
Remove snow from the roof safely using roof rakes. After a heavy snowfall, using a roof rake to clear snow from the edges of your roof can prevent excessive buildup that leads to ice dams. By removing the snow before it has a chance to melt and refreeze, you reduce the amount of water that can pool behind ice dams. It’s important to use the right tools and techniques to avoid damaging shingles or risking personal injury.
Install Ice and Water Shield Membranes
Install ice and water shield membranes during roof installation. These waterproof membranes are applied under the shingles along the roof’s edges and valleys. They act as a protective barrier, preventing meltwater from seeping under the roofing material and into the home. This is especially useful in areas prone to ice dams, providing an extra layer of defense against leaks and water damage.
Use Heated Cables to Melt the Ice
Use heated cables in some cases to melt ice dams. In situations where ice dams are a persistent problem, electric heated cables can be installed along the roof’s edge to melt ice and create channels for water to drain off safely. While this is generally considered a last resort due to energy use and installation costs, heated cables can be an effective temporary solution during severe winter conditions.
Removing an Ice Dam That Has Already Formed
Removing an ice dam that has already formed requires caution to avoid damaging your roof or causing injury. Here are some common and effective methods.
Use a roof rake to remove snow: The easiest and safest way to address an ice dam is to remove the snow buildup on the roof before it melts and refreezes. Using a long-handled roof rake from the ground, carefully pull the snow off the roof, especially near the eaves where ice dams form. This reduces the source of meltwater feeding the ice dam.
Apply calcium chloride ice melt: To break up the ice dam itself, you can place calcium chloride ice melt in a nylon stocking or pantyhose and position it vertically over the ice dam. As the calcium chloride dissolves, it creates channels in the ice that allow trapped water to drain off. Avoid using rock salt, as it can damage roofing materials and plants.
Use warm water cautiously: Pouring warm (not boiling) water over the ice dam can help melt it, but this method carries risks. The water may refreeze lower down the roof or on walkways, creating hazardous ice patches. It’s generally safer to combine this with other methods or use it sparingly.
Hire a professional: If the ice dam is large, persistent, or causing leaks, it may be best to call a roofing or ice dam removal specialist. Professionals like those at Jackson Contracting have the right tools, such as steamers, to safely remove ice dams without damaging your roof.
If you’re unsure about removing an ice dam yourself, consulting a professional is the safest option.
