I am replacing a deck.  I am planning Ipe decking in a nice geometric pattern.  I also want the space under the deck to be dry.  My current plan calls for a EPDM membrane installed under the decking to feed interior gutters and downspouts to French drains — all good.  Not terribly complicated!  BUT…the membrane is expected to have troughs between the floor joists down which the water drains to the gutters.  BUT, with a pattern in the decking I’d need bracing between the floor joists to affix some of the decking in the pattern to.  How do I do that?  The bracing would interrupt the joist bay where the membrane would trough.  I am open to any suggests such that the underside is dry and I can do the pattern.  Ideas?  Thank you.