Preventing Ice Dam Damage

By Murray Anderson

Ice dams are created by a ridge of ice forming at the edge of a roof. The ridge begins as melting snow that runs down the roof until it gets over a cold spot (i.e over the soffits) and freezes. This ridge of ice or ice dam prevents melting snow from running off the roof so it pools up behind the dam, eventually working its under the roofing shingles and even down into the house where it can cause significant damage to insulation, ceilings, walls and even furniture. 

Ice dams care caused by an interaction of heat loss from within a house, snow on a roof, and temperatures above 32° F on the top portion of a roof. There are a number of things you can do to prevent ice dams and subsequent damage, here's some ideas.

Eliminate snow/ice build up on your roof

• Use a roof rake or even a stable broom to remove snow from your roof.
• Shoveling snow off the roof will also obviously eliminate the potential for run off water, but it's dangerous to walk on a snow covered roof and roofing materials are easily damaged. This is a job best left to professionals.
   

Ensure adequate insulation in your attic

• Warm air from your home migrating into the attic can raise the temperature of the underside of your roof enough to start melting snow - particularly when combined with a warm sunny day. The minimum insulation value for new homes in cold areas of the country is R 38, but many older homes don't have that amount of insulation. Ensuring your attic insulation is at last R38 will help prevent ice damming.
• Insulate and block off any openings into your attic. Just some of these areas include, attic access hatches, potlights and ceiling fixtures, plumbing stacks, HVAC ducts (exhaust fans for example). However, putting insulation too close to a pot light or ceiling fixture can be a fire hazard, so adding insulation close to these types of fixtures may be a job for a professional.
   

Make sure your attic is properly ventilated

• Proper ventilation helps keep your attic temperature similar to that of the outside air and cools the underside of your roof preventing snow from melting. Common  guidelines suggest a minimum 1 square foot of free ventilation area for each 300 square feet of attic ceiling area when there is a vapor barrier at the ceiling
• Ensure the area over your soffits isn't blocked by insulation and the soffits are open to the outside air to provide adequate openings for proper ventilation. A roof overhang of 12 inches or more should provide ample space for inlet (soffit) vents.
• Adequate upper ventilation to ensure proper and continuous air flow in also required. Either continuous ridge vents or a number of individual roof vents normally will provide this upper ventilation. 
   

Protect your roof

• Installation of drip edges or ice shields at your eaves will direct water right off your roof and into the gutters.
  Installing a water proofing membrane along the lower edge of your roof (extending back from the edge at least 24") helps keep water out of the roof. Water proof membranes or 'ice shields" are often a building code requirement ands they do prevent roof damage. 
   

Murray Anderson is an experienced freelance writer over 500 articles published on the web as well as in print magazines and newspapers in both the United States and Canada. He writes on a wide range of topics and is a regular contributor to DoItYourself.com. He can be contacted at murand@lycos.com.