There will be very little shrinkage with Ipe so keep that in mind. A small space for drainage would be recommend but I do not think it is required. Special clips are typically used for hold down as well as spacing. Theses clips are available at Advantage Lumber.
Allow 1/16″ gaps between deck boards. This space is ideal for proper for air circulation, water drainage along with wood contraction & expansion. For Ipe decking, the average rate of shrinkage is roughly 1/16″ on 4″ wide boards and 3/32″ on 6″ wide boards. You may see less shrinking in humid climates. Ipe Clip hidden deck fasteners do allow for the proper expansion and contraction and help you space the boards properly while giving you a deck surface that's free from screw holes.
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