In the roof strength test, a metal plate is pushed against one side of a roof at a displacement rate of 0.2 inch per second. (iihs.org)
In this test, a metal plate is slowly pushed against one side of the roof until the roof is crushed by five inches. (bestride.com)
In typical roof assemblies, this moisture is driven inwards through vapor permeable roofing papers / felts into plywood and OSB roof decks, and subsequently through the other side of the roof deck into the attic space. (buildingscience.com)