We're making a roof terrace using wood deck boards. The two sides of the deck board differ, with small/large grooves. Which side should face up, is this purely an aesthetic choice or is there something else to consider?

Our wood deck boards

I've read about looking at the wood grain, to make sure the planks expand/curl the right way when getting wet, but I'm not sure whether this is correct.

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    This is more appropriate for DIY SE. You certainly don't want to be walking on the deeply grooved, crenellated side. Usually these boards are flat on one side, so I'd go with lighter grooves up. Those small ribs are supposed to be for grip, but they actually don't work very well, and the way they hold moisture will rot things out faster. – jdv May 19 at 19:12
  • Thanks for your answer. Good that you mention walking on it (with bare feet), I didn't consider that. I've asked a moderator to move this to DIY. – Tim Visée May 19 at 19:54
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    You'll probably want to ensure that you've got a bit of slope along the length of the decking to encourage the water to run through the groves, off the decking, and into a suitable drainage system. In that regard, the larger grooves may work better for drainage. However, the smaller ones would definitely be more comfortable for the bare footed. As a shoe wearing person, that wouldn't concern me! – FreeMan May 20 at 16:30
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    On the other hand, I recently laid flat boards (no groves at all) on my deck and don't have any significant issues with it being overly slippery when wet. – FreeMan May 20 at 16:31
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    The deep grooves are there to help control cupping. – Kris May 21 at 23:20

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