What are ice dams and what causes them?
Two things are necessary for ice dams to form: snow on your roof and temperatures below freezing (32°F). Any areas of your roof that are warmed to temperatures above freezing will cause the snow to melt and refreeze as it reaches the colder roof edges, forming a ridge of ice known as an ice dam.
Heat loss can be the result of many things and is the most common cause of ice dams. The warm air in your home or heat transferred from your chimney to the attic space may escape through cracks or gaps in drywall, light fixtures, plumbing and other ceiling penetrations or through inefficient insulation.
Exhaust fans like the ones in kitchens or bathrooms may also melt the snow if they’re not vented outside your home. Any heat that escapes will warm areas of your roof, melting the snow and ultimately lead to the formation of ice dams.
Once ice dams are formed, they will prevent additional snowmelt from draining off presenting a number of challenges for homeowners.
Any additional snowmelt will back up behind an ice dam, flow under the shingles, and into your house. Interior leaks can damage your ceilings, floors, insulation and walls. They can also promote mold growth if any wet areas aren’t properly dried out.
Ice dams and the removal of them can damage your shingles and gutters. This damage can also result in interior leaks.