ipe decking over a roof and pool deck - concerned about cupping
1) I am about to build a deck over a flat roof (slight pitch of 1/8"/1') that has reasonably good drainage. As with any flat roof there are some small areas of pooling. I was planning on using Ipe and am concerned about it cupping. The deck will be 2"-8" above the PVC membrane. I am in Los Angeles and there is usually very low humidity. The house is on the top of a ridge line and there is usually a moderate updraft; however, sometimes the air is still.
2) Another portion of the project is a pool deck. The deck is designed to be 6" above grade and the grade is currently dirt/fill. It is a "WET" area that will often get water from entrances/exits of the pool. What should I do to the subdeck area to prevent cupping so that I don't have to lift the deck 12" above the ground?
would using 5/4 x X make a difference and if so is it worth the 25% additional $?
does the spacing of the boards make much of a difference and what would be recomended? (it is going over a white PVC roof membrane so the tighter the treads the more attractive).
How valid are these concerns?
Is there a way to minimize risk?
I looked at some of the engineered products and they have similar requirements for ventilation. The engineered products are more expensive then the Ipe and I would prefer to use the Ipe but don't want to regret the decision.
The roof deck area is ~2000' and the pool deck is ~700' so the investment in lumber and installation is considerable.
I have used Ipe in Miami for docks and never had any issues. I really like the material and would like to use if practical so whatever suggestions you may have would be appreciated.