Yes, this is FORBIDDEN, but it also assumes new cap over new cap.
The old cap had white granules and has lost a lot of them - the roof is almost black now.
IF there were no granules, I am confident you could successfully blue down the new cap sheet. (I’m guessing the failure mode would be thermal expansion/contraction that would separate the granules from either their old cap or from he newly glued cap.)
So I am thinking of pressure washing the old cap to blow off as much granules as possible and NOT use new peel-n-stick cap, but rather old school bucket of adhesive and plain new cap.
I don’t want to nail down another glue sheet and then cap because 1) it puts nails through the existing with is in good shape and 2) there will be an air gap between the nail sheet and the old cap - and when there are gaps like that, there is always the possibility of water finding its way there which leads to other problems.
I know that Ames Research elastomeric coating would bond (and other products too), so I don’t see why it is impossible to bond another cap sheet.
So what am I missing? Opinions? Criticisms?
Thanks so much in advance,