We are planning on putting in a new wrap around deck approx 300 sq ft. We lives in Chicago suburbs so get cold dry winters and relatively humid summers. Front part is going over current covered concrete porch (raised on top of 2x6 joists). I know it isn't an ideal height for this section but it is raised and doesn't receive a lot of moisture since it is covered. The rest of the deck will be 15in raised. Sides and front will be vented with lattice with exception of stairwells. We are planning on face screwing to keep it more secure. We will be sealing it on bottom and sides with Anderson Clark, sealing cut ends with the wax, and sealing the top once it is laid. Hoping with the amount of ventilation as well as sealing all sides, it will minimize cupping. I was planning on using 1x6 air dried ipe, however, we are pushing our budget. I am trying to figure out if we can get away with the 1x6 or 1x6 plus kiln dried Cumaru to cut costs a bit, or if I am just asking for trouble with this design. Other thing to note is my husband is adamant about minimizing gaps between boards. I already told him no gaps is practically guaranteeing problems. But with the amount of shrinkage in Ipe we could probably get away with 1/16 as some places recommend. Reading Cumaru recommendations everyone seems to say 1/4 gap which just seems excessive, especially if it does shrink in the winter a bit. Also, considering how dense both of these woods are, does anyone have any experience with how much they actually expand? I find a lot about ipe shrinkage, but am struggling to find info for ipe expansion as well as shrinkage/expansion in the Cumaru.