I have a 2-car garage that is not cooled or heated. Above the garage is an attic/loft space. The attic has beams (they are large beams, not 2-by-4s) that are spaced 16 inches apart. The beams have pink fiber insulation in-between them. The insulation has a vapor barrier on the underside. I did a lot of research online and think my questions will apply to a number of people. I couldn't find a single source that answered all of my questions.
1) Before I add a plywood subfloor do I need to add an additional vapor barrier (the insulation already has one)?
2) I watched a Georgia Pacific instructional video on YouTube and they said to leave 1/8 of an inch in-between the 4x8 plywood boards, I thought you were supposed to butt them up against one another?
3) Will 1/2 inch thick plywood work in my situation?
4) What kind of screws should I use? Will 1 inch decking screws work?
5) Should I lay the plywood perpendicular to the beams?