We are currently getting estimates to have the roof replaced on our 15 year old, two story colonial. We live in Syracuse, NY where the average yearly snowfall is 115.6". Would it be okay to have the new roof installed over the original roof? I know "roof overs" are done all the time but I worry about the extra weight that this would add in addition to the snow. The tear off would involve new flashing, rubberized leak barrier on eaves, valleys and etc. I assume that in most new construction they don't put down leak barrier. What are your thoughts? Thanks.