Hot take: People keep putting their new deck boards too close together
I just finished my deck in the backyard and my neighbor, who built his last summer, asked why I left a gap. I used a 16d nail as a spacer, about an eighth of an inch, between each pressure-treated 2x6. Wood needs room to swell when it gets wet, or your whole deck turns into a wavy mess. Anyone else in a humid area like Georgia have a different spacing trick?