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Community and Q&A

Good Breathable P&S Synthetic Roof Membrane

jackofalltrades777 | Posted in Green Building Techniques on

Looking for a good breathable synthetic peel & stick roof membrane that would would well underneath an elevated (purlin) metal roof. Most P&S membranes I have seen are not breathable.

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  1. Expert Member
    Michael Maines | | #1

    Why do you need the membrane to be breathable? (I'm assuming by "breathable" you mean vapor-permeable.)

    1. jackofalltrades777 | | #4

      Yes, vapor permeable. Why? I will have spray foam underneath OSB sheathing.

  2. Expert Member


    Elevated on purlins over plywood roof sheathing?

    1. jackofalltrades777 | | #5

      OSB roof sheathing and then the standing seam metal roof will sit on steel purlins.

  3. Expert Member
    Akos | | #3

    Very few options out there you can look at SlopeShield Plus SA.

    For a lot of roof structures, permeability of the underlayment does not matter much and there are cheaper ways to air seal than full peel and stick. Before spending the money on it, I would make sure that it is actually needed for your roof.

    1. jackofalltrades777 | | #6

      Thanks! I'll check out SlopeShield Plus SA. Looks like it has a 30 PERMS rating

      I will have closed cell spray foam underneath the OSB roof sheathing so I want to make sure the roof membrane is vapor permeable to allow drying of the OSB sheathing to the outside. Since it cannot dry to the inside.

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