An occasional light snowfall might be no more damaging to your roof than a rain storm. However, snowfall that builds up on your home’s roof is a different story. Normally the eaves and overhangs of your roof will be colder then the rest of the roof because of cold air coming from the top as well as the bottom, in much the same way as a bridge will freeze before the surrounding roads. Melting snow from the roof will run down the roof and freeze, creating a ridge of ice at the bottom of the roof. This ridge acts like a dam for melting snow that runs down the slope of the roof. Ice at the bottom of a roof can accumulate to several inches thick.
Ice built up at the eaves or overhang of the bottom of the roof slope can be devastating to your roof. Snow and ice might begin to build up on the roof and cause stress on the rafters or roof trusses, which might not be engineered to withstand so much extra weight. Built-up ice can also work its way under the shingles, creating water leaks on the insides of the outer walls of your home.
A roof rake can be assembled from materials you might already have. A piece of scrap wood about 6 inches wide and 3 feet long attached to the tines of a garden rake will suffice in an emergency. A more permanent tool with a longer handle can be made from PVC pipe. Assemble the pipe into a T-shape with PVC cement. Drill holes through the top edge of the T and bolt a piece of plywood in place. The tail of the T-shaped tool is used as the handle.
The plywood end of your roof rake is used to push and pull snow off the roof. The handle should be long enough that you can stand comfortably on the ground while using it. It is best to use your rake right after a snowfall before the eaves start icing up. Do not push down on the rake -- let gravity work for you. By doing this, you are not overexerting yourself and you are much less likely to damage the roof shingles.