Should I add new sheathing to a flat roof?
I own an old brick multi family building.
I am planning on getting five layers of an old built up roof torn off and replaced with 5” of polyISO and a TPO covering. Insulating from below is not an option right now.
Longevity and performance is always a top priority for me when getting a major repair done. Is it worthwhile to add an air barrier like zip sheathing on top of the roof deck before installing the new rigid foam and TPO?
Would an alternative like simply taping the joints of the old roof decking help create a good air barrier?
Any advice would be helpful, looking to do this right the first time and not have to worry about the roof for many decades.
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