Great article in the Sept issue of FHB by Joe Lstiburek.  Thanks to his writings, I know how to design around issues of condensation I have with building a Lindal house with a sealed cathedral roof.  Recently BSC also has published articles on the need for a drainage plane behind thin “lick and stick” masonry adhered to wood sheathing to prevent inward vapor drive into the sheathing.  In his recent article “A crash course in Roof Venting” , he recommends “To keep moisture out of the roof assembly, roofing underlayment of 1 perm or less (class II vapor retarder) must be installed under the shingles.”  Since the OSB sheathing is about 1 perm, is this sufficient, or is the vapor retarder recommended as well to keep the OSB itself safe from inward moisture drive as the roof shingles dry under the sun?  Even thin masonry likely holds more moisture than asphalt shingles, but is this also a significant issue?  As additional info, the roof uses OSB, closed cell foam, and batts in that order.  Thanks for the superb information you provide.