Here is how it is done. Get a solid sheet of membane that is around 1/8 of an inch thick. You will need to make sure that your deck slopes 1/4 inch per foot for drainage and install a scupper or drain or some kind. Lay it in the area and use contact cement to adhere it to the plywood base. You then put the membrane up the sides of the wall and have siding or something cover the top so that water can't get under it. You then construct a free floating deck to sit on top of the rubber membrane. It is important that you use a router and completely round over any edges that touch the membrane so that it doesn't get cut. If you have more questions, please let me know.
Water dries, rocks crumble, and trees die. The only thing that is eternal is the reputation we leave behind. - Ancient Viking Proverb
