What Is a Safe Way to Melt Snow on a Roof?

Recognize Problems

• Avoid unnecessary risks by being certain that the snow warrants removal. Be aware of how much snow the roof can withstand and note any areas of drift or especially high accumulation. Symptoms of snow-related roof problems include sagging; leaks; cracked or bent supports; cracks in wooden members, walls or masonry; doors and windows that have popped open or are difficult to open; bowed utility pipes; and creaking, popping or similar noises. It may be dangerous and unnecessary to clear the entire roof of snow if heavy accumulation is occurring in only a few spots.

Heating Cables

• Heating, or de-icing, cables can melt some amount of snow and ice off of a roof. The amount and arrangement of cables can vary to suit different needs, but the cables must loop or extend beyond the bottom edge of the roof to ensure that drainage is adequate and water will not back up behind an ice dam. De-icing cables require an electrical hookup and will be most effective if some amount of snow is manually removed before they are placed.

Chemicals

• Certain chemical de-icers can melt snow and ice on a roof but offer the greatest relief if the amount of snow is minimal and the agents are strategically placed. De-icers will be most effective at preventing or remedying an ice dam if they are placed in small piles every few feet above the ice dam. Also, widely spreading de-icers across the roof can melt a significant amount of snow. Although effects may appear minimal, de-icers can increase the air space in snow and greatly reduced the load. Be wary of de-icers, that contain oxidizing agents like sodium chloride or calcium chloride that corrode metals and deteriorate roofing materials. Safer de-icing materials include urea, potassium chloride, ammonium sulfate and calcium magnesium acetate.

Manual Removal

• Save for a uniformly heated roof or well-placed heating cables, manual removal of snow using a specially designed snow rake is generally the most effective method. A push broom may also be used. Start from the edge of the roof and work inward. Rather than scrape the roof clean, which risks damaging roofing materials, only scrape down to two or three inches of snow. This can be performed from a ladder. Be careful when working on a ladder: Remove only a small amount of snow at a time, avoid overreaching and push snow so that it does not fall on the ladder user. You can push snow from above if the roof has windows from which you can work, or if the roof has a minimal slope or landings to prevent falls.