An ice dam is a piece of ice that forms along the edge of your roof. It is caused when the warm attic causes snow to melt, run down the roof and refreeze on the cold edge of the roof. Ice damming can also be caused by melting and freezing during unseasonably warm winter weather. When the snow melts in spring, the water can run down the roof and back up under the ice dam and seep through the roof and into your home.
Preventing ice dams
You can prevent most ice dams by having a cold roof. There are a few ways to accomplish this.
- Close up attic bypasses
About one-third of your heat is lost through the ceiling and into the attic, through gaps in drywall, around light fixtures, plumbing pipes, chimneys, and access hatches. Air leaks can be plugged using foam or caulk. As an added bonus, you’ll save energy and reduce heating and air conditioning costs.
- Measure your attic insulation depth
Building codes generally require 12 to 14 inches of fiberglass or cellulose. Add more if you have less than 8 inches. Blown-in cellulose and fiberglass usually fill more tightly around rafters and joists than hand-placed batts.
- Add roof and soffit vents
Attic ventilation draws in cold outdoor air and flushes out warmer attic air, cooling both the attic and the roof. Blown-in insulation can sometimes block airflow. A blast of compressed air should be enough to clear a blocked vent, and baffles can help to prevent blockage from occurring. Low slope roofs, flat roofs, roofs with skylights, and roofs with no attics are especially difficult to vent and it may not be possible to do so.
- Use an ice and water barrier
The next time you reroof, use a self-sealing ice and water barrier and shingle overtop of it.
- Use a snow rake
Rake the snow off your roof after a heavy snowfall with a snow rake if you live in a one story home. NEVER use a snow rake while standing on a ladder! Be very careful while doing this, as shingles may become brittle and break in cold weather.
- Install heat cable
These are high-resistance wires that are mounted on the edge of the roof (zig-zag pattern) and plug into an outdoor GFCI outlet. You’ll want to run the heat cable down your downspouts to prevent ice forming in your gutters and downspouts.
- Steam the snow off
Hire a roofing company to steam the snow off the roof – it’s like a hot water pressure washer – to melt the ice away without damaging the roof.
- Avoid chipping off the ice with a hatchet or ice pick, as these tools can break or puncture your shingles.