I have written about oriented strand board (OSB) a number of times before. The topic most often comes up when talking about L-P innerseal siding. However, OSB is available in sheets as well and is used for other applications such as sheathing that is covered by other material.
This photo below is one of the most unsuitable applications I have seen forOSB. The key to longevity, for this product, is keeping it dry. It is a shredded/chopped/glued back together wood product and, when moisture can get into the edges, ends, soak down into the top, it does not weather a whole lot better than a cardboard box. Now, in theory, the OSB sidings are made to be more durable -- if they are installed exactly right and kept painted, caulked and maintained.
The photos below show exposed trim that is cut from OSB. It was buckled, warped and de-laminating/decaying in a number of different locations. In some places they had tacked a metal flashing over it, to protect it but this was not working well at all. The second photo is closeup, so you can have a good gander at it.

Thanks for dropping in
Bellingham WA home inspections
Steven L. Smith




Charlie,
That pressure treated OSB is a Seattle phenomenon, like grunge. Can you please blog on it and I will send a link to your work.
Ryan,
Yes, even with lumber it is not unusual to see it warped or with some decay at rafter tails where roofing drains over it, if there is no shingle extended over the rafter tail or fascia. However the OSB is really unsuitable in that application.
Ryan,
I think it might be really good in some of the dry climates. But here in the Pacific NorthWET it takes lots of maintenance to keep it from turning into a sponge.