We purchased a house this summer, and three days later after a big rain, the roof leaked. Needless to say, we wound up replacing the entire roof, as there was no way to repair it.
We ordered up new trusses, and steel for the roof. We installed the trusses with perlings and then laid the steel over top. I couldn't get a straight answer out of anyone regarding tar paper.
I have vented soffit on three sides and a ridge vent the entire width, which is 12' I have only insulated with R-30, which is 10", so far, was going to do a better job and add some more insulation before sheet-rocking.
My problem is, I pulled the edge of my plastic and one piece of insulation down so I could run my plumbing stack through the roof, and I have condensation on the underside.