Tuesday, January 20, 2009

Should Roofs Have Snow Removed?

A interesting local myth, sage advice, etc. for winter emerged. Should snow be removed from roofs? The reasons are two. The weight of the snow could collapse the roof. And the thraw freeze cycle can cause ice to build up under shingles and cause the roof to leak. First the weight issue. Modern home roofs are designed to hold 40 lbs per square foot. So how much does snow weigh. A little googling and the density of snow can be found. New fallen light fluffy snow has 15% of the density of water. Snow that is wet and heavy has up to 50% of the density of water. Water has a weight of 1gm/ml or approximately 7 lbs/gal. Or approximately 7 lbs/sq ft. So at the worse snow weighs 3.5 lbs/sq ft. At the best is weighs 1.05 lbs/sq ft. So that means that for snow to get to 40lbs/sqft there would have to be 11.5 ft to 40 ft of snow on the roof. Another observation. Have you ever been up on a roof? If so have you ever stood on one foor on a roof? If you are an average size man that would be 180 lbs on one foot in a space of less than one sq foot. Unless the roof is rotten or poorly designed or made I haven't heard of anyone going through there roof ending up in their living room. The next point I had to ask an expert. My brother in law is a professional roofer. He advised against removing snow from the roof. In his over 25 year experience he has never had to replace a roof because it leaked due to someone not removing snow from their roof. He said roofs with eves are designed to handle the problem. Another reasons is it can be dangerous. I know of people who have gotten up on their roofs to remove snow and fallen off and got killed, maimed or worse. I know of one individual who is brain dead now because he fell of the roof trying to remove the snow. Next, the only reason to do it is if you got too much money and want to spread the wealth around, but you better have good liability insurance if the guy you hire falls off the roof.

Skeptical DoDo

No comments: