I have a 10x10 outside shed which is in need of a new roof. Since the shed has only 1 layer of shingles and they are relatively in good shape, I plan to cover over the 1st layer of shingles. One question: in caping the peak, do I remove the 1st layer of shingles on the peak, or do I simply lay the 2nd layer dirctly over the 1st layer of shingles?