I've just installed garapa decking in a new construction home - deck has been in place about 8 weeks and has not yet been sealed - after one rain many of the boards have 'cupped' on the upper surface. Possible underlying circumstances: (1) the underside of the deck is relatively confined, with limited ventilation (I have plans to add ventilation before more rains appear); (2) boards were installed with ipe clips, not nails or screws, so spacing is relatively close; (3) there is a pool pump system under the deck. Regardless of these factors, I'm still really surprised that a wood supposedly as dense as garapa would deform after one rain.
Any thoughts on what might be happening will be appreciated. thanks!