A damage free rooftop should hold about 20 pounds of snow per square foot before it puts a strain on the roof. Because houses have different structures and roofing materials, one house may be able to handle more snow than another can. Ten to 12 inches of fresh snow is about five pounds per square foot. It only takes three to five inches of impacted snow to equal that same amount on a rooftop. One inch of ice is equivalent to one foot of new snow.