3/4" or 1.5" thick roof ?? - Choice Made

[afreegreek]

So what thickness of plywood for the actual roof. I have a flat roof and thinking 1/2 inch maybe 3/8 or Eden as thin as a 1/4 One friend suggested 3/4 not sure I want that thick. Spars about every 12 inches.

you could go down to 1/8" if you buy a good quality sheet. most 1/8" ply is door skin grade, 1 thick centre layer and 2 gossamer thin outer layers.. this stuff is too weak but 1/8" with 3 plies of equal thickness is plenty strong..