What is an Ice Dam?

An ice dam is a ridge of ice that forms at the edge of a roof and prevents melting snow (water) From draining off the roof. The water that backs up behind the dam can leak into a home and cause damage to walls, ceilings, insulation, and other areas. FIGURE 1 shows a cross section of a home with an ice dam.

FIGURE 1. Cross section of a one-and-a-half story house with an ice dam.

WHAT CAUSES ICE DAMS?

There is a complex interaction among the amount of heat loss from a house, snow cover, and outside temperatures that leads to ice dam formation. For ice dams to form there must be snow on the roof, and at the same time, higher portions of the roofs outside surface must be above 32 degrees, while lower surfaces are below 32 degrees. When we say temperatures above or below 32 degrees, we are talking about average temperature over sustained periods of time.
The snow on a roofs surface above 32 degrees will melt. As water flows down the roof it reaches the portion of the roof that is below 32 degrees and freezes. There you have an ice dam!!


What Can I Do To Prevent Ice Dams?

Make sure your attic area has adequate insulation. Make sure your attic insulation does not cover your soffit air intake vents. Add soffit vents if your home currently does not have any. Make sure your attic area has sufficient air exhaust outlets (gable vents) and that the air flow is distributed throughout the attic space. Peak mounted ridge vents maximize air flow in attic areas. Products such as an ice and water shield can be installed at the eaves of the home and in valley areas under the shingles which will prevent water from entering the home unless it dams higher than the protection provides. Electric heat tapes can be installed in the gutter guards. In extreme cases heat tape can be installed on the lower sections of the roof to melt the ice before dams are formed.

What Do I Do When An Ice Dam Happens?

The only corrective action that can be taken is to remove the barrier of ice at the gutter line or to remove the ice build-up on the roof area before it melts from underneath. It must be noted that working on a roof under these conditions is extremely dangerous. The risk of injury should always be weighed against the cost of water damage repair.
Also, in removing ice from the gutter and roof, you may cause damage to these areas that will require professional repair. Again, the cost of water damage repair may be less than the cost of a roof or gutter repair.

Who Is Responsible For Ice Dams And The Resulting Leaks?

Ice dams are the result of winter storm conditions. Because they are storm damage related, and not a roof flaw, damage caused by water is not covered by a shingle manufacturer's or roofing companies warranty. Remember, roofs are designed to shed water to the ground.
There are many products on the market to improve the capability of established homes to fend off ice dam leaks. Roofing contractors are able to provide an ever increasing number of products and information for re-roofing clients to choose from.

The final responsibility remains with the homeowner when re-roofing to weigh the cost of prevention and protection products against the possible cost of damage if an ice dam leak occurs.