University of Wisconsin-Extension
Ice
dams occur when a snow-covered roof over the attic is warmer
than the eaves - the overhang of a roof. If the roof is warm,
it will cause the snow to melt and run under snow along the
roof. When the melted snow hits the cooler eaves, it freezes.
As ice builds up on eaves, it eventually traps water behind
it. The water backs up under shingles and finds its way through
seams in the building paper and roof decking to enter the
attic and living area. Wallpaper, plaster and paint surfaces may be damaged in the process. Fortunately, there are several
ways to remedy the problem.
If you
have an immediate problem with ice dams, you should remove
the snow from the part of the roof directly above the ice
dam. This limits the amount of water that can collect behind
the dam.
- Remove
the snow using a roof rake, hoe or push broom. Roof
rakes have long handles that allow you to stay on the ground
when clearing a single-story roof. You can purchase them
at hardware stores.
- Avoid
using sharp instruments, such as axes, to break channels
through the ice. This is likely to cause roof and structure
damage.
A cooler
attic area will help decrease problems with ice dams. Here
are two ways to keep attics cool:
- Increase
insulation in the attic to at least 12 inches. Also,
close any thermal shortcuts -openings that allow air to
move from the heated part of the house into the attic. Chases
around chimneys, plumbing vents, junction boxes for ceiling
light fixtures, attic hatches and ceiling fan mounts are
common thermal shortcuts.
- Create
adequate attic ventilation to remove any heat that escapes
into the attic. One square foot of free ventilation
opening is recommended for every 150 square feet of attic
space. Ventilation should be divided between eaves and the
house ridge to take advantage of the fact that warm air
rises. When installing eave or soffit vents, be sure that
the opening is not blocked by insulation. You can do that
by installing a cardboard or plastic channel over the insulation
lined up with each vent.
Additional resources:
Your county Extension office
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and Reproduction Information: Information in NASD does not represent
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NASD Review: 04/2002
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