For longevity...what about that corrugated pvc roofing material...waterproof, comes in green, covers 16 sqft/panel, seen some for $12.50/piece
You should look for a couple sections of used scaffolding. They are the perfect size around 4x6 and close to 6' high they are easy to set up and move by yourself and you could easily build a top for it.
Iluv2hunt, We've got 2 box blinds one is 4x4, the other 5x7. The ceiling heights are about 7' so no problem standing up. Both are sided with plywood, both have flat standing seam metal roofs, don't need to have a pitch with that type metal. To me this type of construction is more safe than a pop-up on a platform and the window sills provide a good rest for your rifle. Have some old executive style office chairs to sit and sleep in. But then again I'm an old man and can't take the elements like you young bucks! Sat in the 4x4 this afternoon, it was about 45 degrees and a nothwest wind of about 15 mph and I was fairly comfortable. When it gets much colder I will break out the little propane portable heater, in fact if it wasn't doe week I would have stayed at the house! :rolleyes Treefarmer
We used to cover ours with roofing paper. Had to replace every couple of years but it worked well.
If you're just trying to keep the cost down, check Craigslist and Freecycle.org for plywood. I see people giving it away or for cheap on Craigslist all the time. Couple of weeks ago somebody in Bradenton had sheets of 3/8" for $12 ea. He had 80 sheets and you had to buy at least 8 sheets.
