What Are the Causes of Ice Forming on the Edge of a Roof?

Melting Snow

• The No. 1 cause of icicles and ice dams is melting snow. When snow forms on a rooftop, it sits and waits. As rising temperatures and direct sunlight heat the snow, it begins to melt and slowly move down the rooftop. In heavy winter, the temperatures outside are still too cold for the melting snow to stay fluid; therefore, the snow accumulates in the gutters and edges of the roof where it freezes. This forms an icicle or ice dam.

Roof Insulation

• When temperatures outside are below freezing, but the snow on a rooftop still melts, the roof or attic's insulation is to blame. Poor insulation can allow heat to escape warm areas of the attic or ceiling of a home, which in turn melts the snow in patches. The melted snow then runs until it reaches a cold area of the roof and refreezes into ice dams or icicles.

Gutter Debris

• Gutters provide an area for snow and rain to run off, but they are prone to collecting debris such as leaves, branches and dirt. Excess debris causes melting snow to build up and block a gutter, rather than drain out as it should. As the water accumulates and the temperatures cool, the water freezes, which causes an ice dam or icicles to form.

Prevention

• Homeowners can take special precautions to prevent ice dams or icicles from forming on rooftop edges. The first step is ensuring that there is proper ventilation and insulation in rooftop, attic and ceiling areas of the home. Make sure that warm air does not escape the house, which can cause snow to melt. Clean out gutters frequently to remove debris and blockage, which prevents snow runoff from draining properly. Never attempt to remove gutters that are full of ice dams or chisel away at ice dams that have formed. This not only can cause a sheet of ice to fall and cause injury, but can permanently damage a home's gutter system or rooftop.