What is the best WRB membrane or house wrap for a roof sheathed with plywood?

To choose between a waterproof or breathable weather barrier membrane you need to decide what you want it to do, whether it has to let moiture in or keep it out.When you say your roof is going to dry to the inside, I’m wondering exactly what you mean so we can be sure to steer you correctly. Where do you live orwhat is your climate zone?I ask because a roof in a cold climate needs an interior vapour barrier.

Here is our page onchoosing the right WRB weather barrier membrane, but it sounds like it’s on the outside of the sheathing just under metal roofing if I’m reading that right, so if that’s the case there is no need for it to be breathable, best to have it waterproof since it is acting as a drainage plane. I’m just not sure what your intention is with an insulated roof with mineral wool insulation and no vapor barrier unless you’re in the southern US where your insulation is to keep a house cool not warm. We advocatedbuilding basement walls with no vapor barrier to prevent mold, but above grade walls and roofs are a different beast and I just want to make sure you didn't absorb our basement building guidance and apply it to a roof. We can probably help but we need to know where you are first.

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