You noticed that icicles form at the edge of your roof, but your neighbors do not have any? This is a sure sign that you have an attic insulation and ventilation problem. When snow accumulates on the roof, here is what it can happen to it: (1) evaporate from the action of the sun, (2) melt if the outside temperature is above the freezing point, enter the gutters and flow to the ground or …

(3) melt, if the outside temperature is below the freezing point but the temperature inside of your attic is high enough, and build up as ice dams and icicles at the edge of your roof.

In the same series of articles:

Why ventilate your attic?
How to Control Moisture in Attics
Attic Moisture and Your Climate
How to Fix a Water Stain on a Ceiling
How to Prevent Icicles and Ice Dams on Roofs
Why and how to install an attic vent
13 possible spots for your roof leak
20 point roof inspection check list
How to replace faulty roof shingles

The key factors in ice dams forming are the outside temperature and the temperature within your attic. Should the inside temperature of attic is high enough to cause the snow on the roof to melt but the outside temperature is low enough to refreeze the water at the edge of the roof ice dams are formed. Ice dams are growing heaps of ice that blocks path of the melted snow.

Why Should You Care?

Once an ice dam increases to a certain height, the melted snow that pools up behind can suddenly leak back under the roof shingles and then into your home. The warmer your attic, the more melt off will occur at the roof surface and the larger the amount of water leaked in. On roofs with small slopes, it only takes a small ice dam to cause water backup and leakage.

Water leaking into your home can easily translate into water damage to your home and costly repairs.

Here are the most common examples of water induced damage:

  • water stains on the ceiling
  • mold, mildew and rot on any of the roof framing or sheathing
  • deterioration of attic insulation

What to Do?

The answer to the ice dam problem is preventing the snow from melting by decreasing the temperature in your attic.

How do you do that? Stop any significant heat leakage into the attic by adding enough insulation onto the attic floor and by making sure the attic is properly ventilated. The usual recommendation for venting is 1 square foot of vent for every 150 feet of attic floor area.

In terms of how much insulation is enough you can consult here the standards and recommendations for:

What Not to Do?

Here are some wrong solutions to an ice dam problem which may alleviate the symptoms of the problem but do not address its root cause.

  • Making the roof impermeable by using a self-sealing membrane under the shingles. The membrane do not prevent ice dams from forming, they just stop the water from leaking through the roof sheathing while ice dams may still damage your shingles and gutters. Some homeowners have found this method expensive and ineffective.
  • Attaching electric cables which will melt channels in the ice. This solution increases you electricity bill, it only alleviates the problem, and it may not work as expected.
  • Removing gutters to prevent them from becoming ice traps. The gutters are meant to keep roof water away from your basement, and contrary to popular belief they do not cause the ice dams.
  • Removing ice dams every winter with an axe or ice pick. This is a very effective way to destroy your shingles and potentially hurt yourself by falling off the ladder.
  • Applying salt or ice melting chemicals on the roof. Although the salt will melt some of the ice, it will not prevent the ice dam from forming again and again. Moreover, in short time you will notice shingle damage and gutter corrosion along with other environmental damage.

In the same series of articles:

Why ventilate your attic?
How to Control Moisture in Attics
Attic Moisture and Your Climate
How to Fix a Water Stain on a Ceiling
How to Prevent Icicles and Ice Dams on Roofs
Why and how to install an attic vent
13 possible spots for your roof leak
20 point roof inspection check list
How to replace faulty roof shingles

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