Bottom Line: I don't buy the hype that "bark side up" is always the answer and I'll tell you why. Then you can decide which way you want to install the boards.
Boards typically come in three cuts:
Why Boards Warp: When deck boards get wet they do not get wet consistently. That is, the wood exposed to the rain and the wood on the bottom of the board are not being exposed to the same moisture. As a result, the wood fibers on the weathered or exposure side expand more than the fibers on the bottom. That creates dimensional changes in the wood. Wood warps the opposite orientation of the growth rings. The orientation of growth rings and which side gets wetter determines the way the wood warps on your deck.
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