[note I put an apostrophe between the i and the m after 'cozz and the spell check was happy. but it doesn't work for cozz]
you used the same or similar material for your roof ? what size was it and over time did you notice the roof sag more ? 'cozz i'm thinking i could do it with out roof beams . but over time it would stretch and sag.
"The water can be collected by splitting a plastic pipe lengthwise and snapping it over the edge" . the edge of what presicly. so i got a bag/tarp sandwich and the water will collect where bag meets tarp. my idea was to lay a channel between the bags, but above the tarp. these channels between the bags will run to the outside edge of the bag.then i build a gutter below that to collect it that runs the length of the wall to the drain. if i make it with the gutter below both tarps i can do the same with the bottem tarp for when the top one starts letting in water.for sure i would like to put a propper roof on . but later once ive saved up for it.