Second layer of shingles question
I want to put a second layer of shingles on my garage roof. Can someone explain the proper technique? In particular, I think it will be best to align the top of each shingle in the second layer with the bottom of the tab of a shingle in the first layer. This will allow them to lay as flat as possible. However the first course will be less than a tab height - maybe 4 inches high instead of 5 inches - because of the way the shingles overlap. Is that the way it is supposed to be done?