OSB Grades

There will be a stamp on each sheet, usually near a corner, that says the grade and standard that it conforms to if originally it was a batch for UK consumption. If used for the purposes you mention then I'd expect it to be the more water resistant OSB3.

Andrew

I know there often will be. A lot of it wasnt intended for uk sale, a lot has enough damage to render the marks illegible, and a lot is in smaller sheets than originally made.

I dont expect to get any OSB1, and it can presumably be weeded out with an ovenight soak. But how to tell 2 from 3 I really dont know.

NT