If it's not dried, stack and sticker where there is good prevailing air movement with just a cover on top so that precipitation doesn't stand on top of the wood. If it's try, you can store in a more closed, but still ventilated place. I use a 10'x10' Shelter Logic tent for my outside lumber storage that's on top of a simple platform built with pressure treated materials for the frame and exterior plywood for the floor. It's not a permanent structure (short posts to level are sitting on concrete pavers) so I had no zoning issues with it. The try lumber kept inside is not stickered and just organized by species so I can easily get to things. Note I don't keep my "best" stuff out there...it's more my utility lumber.