I am building a deck that floats on a low slope 12 by 24' roof with a pitch of =BD" per foot. The roof and porch have been designed and built to accept the weight. I will cover the roof with an EPDM membrane.
I am just looking for best guesses. I would like to have the deck flat by using tapered 2X joists from 2" to 6" to match the roof slope. I can not go any wider then 2" on the skinny end of the rafter. I am concerned about cutting and using green treated thinking the skinny ends will dry and warp before I get the composite decking attached/screwed? Cedar would be an easier wood to work and not have the problems of green treated. But will it last as long as treated if I put a finish on all sides? Is 20 years overly optimistic given that it is on the north side of the house? =20 thanks