I just read your response to the question about what kind of roof sheathing to use. Because I know you love technical details, I thought you were the perfect candidate for our question. My contact at Weyerhaeuser and I have discussed this issue at length. The American Plywood Assoc, of course, approves OSB for roofing applications. However, some roofing manufacturers, GAF comes specifically to mind, don't like it. Reason: If installed so that the sheets are too close together, they could swell excessively and cause the appearance of buckling, defective shingles. Apparently, OSB is more prone to swelling than CDX. Your point about saving trees is well taken.
Good point! and another example for the need to adapt construction techniques when using new materials. OSB does expand more than plywood and requires some gaps at the joints. OSB must also be protected from rain.
By the way, I understand that OSB is a very good product for high impact areas like the inside of horse stall wall, it seems that it holds up well to hoof damage. George
*For more information on roofing materials and styles, see The Sound Roof .