How to Deal with Your Roof: Ice & Snow
Severe winter weather brings dangerous ice dams that accumulate on rooftops. These ice dams can damage roof systems and also allow melted snow to enter the home. They can also form dangerous icicles and ice packs on the home’s perimeter, posing a hazard to pets, people, and shrubbery.
How Ice Dams Form
Ice dams most often originate when snow on the roof is melted from the underside by heat escaping from the living space. The melted snow runs down the roof until it hits the cold overhang or porch roofs, where it re-freezes. The ice builds up in layers, and eventually, water is trapped upslope of the ice. That trapped water can enter the roof system and the living space, including the walls, the basement, or crawlspace.
Ice dams sometimes occur at the base of valleys on the roof due to sliding snow’s “logjam effect.” With a metal roof in particular, if the sun comes out with snow on the roof, it melts from the underside as the heat is reflected outward, causing it to slide. If it packs too heavily into valleys, ice can form.
How to Manage Ice and Snow on Your Roof
Snow guards can be installed on the roof upslope of valleys to hold the snow load. Guards installed on the structure’s eaves help the snow break up in chunks as it exits the roof rather than in one fell swoop. My general theory on snow management is to break up the snow so it doesn’t block doorways or cause damage on the way to the ground.
There are several ways to guard against ice dams formed by heat escaping the building and melting the snow load:
- Seal air leaks from the living space, including around light fixtures and air conditioning vents.
- Increase insulation on the ceilings of the living space, further reducing heat loss.
- Increase ventilation in the attic, ensuring good airflow from intake to exhaust vents, venting escaped heat to the outside.
- Ensure bathroom, kitchen, and laundry vents all vent to the outside and not into the attic.
How Metal Roofs Handle Ice and Snow
I often get asked by people considering a metal roof whether metal roofs end ice dam problems. My answer is that metal roofs are effective but are not necessarily a 100% solution to ice problems. As long as the sun comes out before ice forms, the snow will usually slide off quickly from a metal roof. Of course, steeper roofs shed it more quickly. However, if ice forms from heat escaping from the home before the sun comes out and causes the snow to slide, you will have results similar to other roofing materials.
Snow management involves snow guards and snow rails (which I am not a fan of in many cases). Ice management on a roof requires heating areas of the roof to discourage ice formation. There are many systems for this, but I generally see the best results with designs like the Ice Dam Cutter that extend heat above the living space rather than limiting it to the roof edge.
As always, feel free to contact me if you’d like to discuss your roof and any problems with snow or ice you’ve experienced.
Todd Miller has spent his entire career in the metal building products manufacturing industry. He is president of Isaiah Industries, an organization recognized as one of the world’s leading metal roofing manufacturers. Todd is currently Vice President of the MRA (Metal Roofing Association) and a Past Chair of MCA (Metal Construction Association). Through his website, he strives to raise the bar on standards and practices to provide property owners with the best possible products for successful roofing projects.
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