APA rated 5/8" OSB what side goes out?

[vdotmatrix]

There seems to be a smooth side and a rough side.

I am doing an ove-engineered repair of my pop up camper's corner and had to replace this par tof the floor with this material.

My question is there a side that is more weather resistant or meant to be exposed after priming?

Actually one side will be the underneath on the popup camper....

[pushkins]

Technically no, however for use on flooring>>>>> there will be black stamped writing down the center of the 4x8 and almost always that instructs you to place "this side down" (smooth side).
When used for wall sheathing it makes no difference the strength is length ways (wall bracing purposes), I always face the smooth side outwards on walls simply as it's then uniform across the structure and it is marginally more water resistant before we install tyvek etc...