It depends on where you use it. On roofs, put the side with nailing lines or the textured face up for traction and accurate fastener spacing (the grade stamp then faces the attic).
For subfloors, follow the print—if it says “THIS SIDE DOWN,” install it that way so the rough face stays up for safer footing. For walls, both faces are structurally equivalent; installers often turn the stamped/printed side outward for inspections.
If you’re using an integrated sheathing with a built-in weather barrier, place the branded barrier face to the exterior and tape the seams as specified.
