Causes

• In addition to resulting from freezing rain, roof ice may form if snow cover is present on the roof. If the higher portion of the roof surface is heated above freezing, it will melt, and the water will run down the slope. The warmed roof surface may be caused in part by freeze-thaw cycles, but it often is the result of heat escaping from the home's interior to the roof. When the melted snow runs down the roof, it may eventually encounter a cooler, lower roof portion, where it refreezes. The amount of ice buildup around the edge of the roof increases as more snow melts. Where the roof is warmer above the ice, snow melt can back up as water behind the ice dam.
  
  

Problems

• Roof ice from an ice storm that results in severe, heavy ice accumulation can cause structural problems. Water that backs up above ice dams when part of the roof is above freezing temperatures can eventually penetrate the roof and create leaks that damage ceilings, insulation and other items and structures.
  
  

Mechanical Ice Removal

• Ice may be removed manually, but this can be dangerous and may damage roofing materials. Snow rakes or brooms are specifically designed for snow removal on roofs. Taking the snow off the roof will decrease the amount of melt and will allow better access to the ice. Use a tool such as a sledgehammer that will not cut into the roofing to remove roof ice, and work from the top down. Mechanical removal can be difficult, and often a combination of snow removal, removing or chipping away a small amount of ice and a drainage-creating technique is the most practical course of action.
  
  

Additional Removal and Drainage Options

• There are additional means to remove roof ice or allow the drainage of backed-up water. Electrical heating cables looped to dangle slightly beyond the edge of the roof will easily melt drainage paths. Chemical deicers such as sodium chloride, calcium chloride, the less corrosive calcium magnesium acetate, potassium chloride or urea can be placed in small quantities in chiseled-out holes spaced every few feet above the ice dam. Another temporary solution to backed-up water is to spray hot water in a stream at the ice dam until a drainage channel forms.
  
  

Long-term Ice Prevention Solutions

• A few actions can have a long-term impact on the likelihood of future problems with roof ice and ice dams. Make the ceiling between the attic or upper space airtight so that no warm, moist air can leak into the attic. Additionally, consider installing additional or better insulation to reduce heat loss through the roof. If these measures are effectively completed, they will decrease the snow melt on the roof.