Are you building this coop on your back porch? I see that you may possibly have a fungas growing ( white within the dark area) on the bottom of the wall on the building (in the photo... between the pen's legs). I hope not! If so, and if it was mine, I would replace those boards, sooner than later, and any others that have this and any dry rot ( soft wood when using a nail or finger nail then pocking to test) on any others as well as on the porch. This may become much more costly in the future if not attended to. I wish you luck!