@Flowerbh, I am so very thankful for the wonderful advice. You are right, cedar is a no-no for chickens. One of the books I have said shavings were the problem but boards were ok, doing some research I found evidence to the contrary.
I see T1-11 mentioned a lot, I have not seeing it a HD/Lowes, but will look for it more carefully. I hope it is not too heavy. That is the hardest part about trying to make this a moveable tractor, finding lightweight materials that are suitable.
I looked for others that had used the corrugated plastic and found mixed reviews. It seems that the polycarbonate is ok, but the cheaper one is not as good. I also see that it can be hard in the heat, planning on having them moving around in the woods/ shaded areas for summer, so hopefully that will work. I am thinking they will only "work" the veggie garden where is very sunny in the late fall to early spring.
thank you again!