Hi all! Been searching these forums here for some time and have found a wealth of great information... thanks...

I'm building a 2 story deck about 500sf... the below portion or the deck is all concrete pavers that connects with an open patio.

The sides of the lower deck is 90% open. The upper level of the deck will have a vaulted roof with an overhang around the perimeter.

The Deck is more like a porch style where the railing are sheathed and finished. The opening are like multiple 4x6 window opening without the windows.

I would say this area is about 30-40% open. The deck is 23' wide and 21' deep (from the house) with the corners 45ed. Lastly the floor system is 2x12 TJI joists with side loaded beams (no posts) and for the lower section I plan to sheath the ceiling for a finished look. (sorry for the winded description, just wanted to give a god picture).

I want to use T&G IPE or possibly Massaranduba as the pricing is much better. The joists are 16oc, and I was planning one ss screw on each joist in the groove and glue on the joist as well...

My questions:

Does anyone see a problem with ventilation as the underside of the floor would be covered? I could add some vents but I'm really not sure if that would be necessary. This should remain very dry and any water would drain. Also regarding the size of the material, any notable differences structurally/cupping wise between 1x4, 1x6 or 5/4x4, 5/4x6 ? I've seen a lot on these very topics but not regarding T&G Covered Deck applications that are expected to remain relatively dry. There is the case where heavy rain/snow along with wind could cause decking surface to get wet but the deck would be sealed with appropriate oil base sealer and likely cleaned... my biggest concerns are with the decking cupping, etc...

Thanks for any help on this, it's much appreciated.