We have a 25x22' slanted roof that we would like to put a composite deck and railings on. The roof is strong enough to support what we want to do. The slant is a 13" difference from the highest to the lowest point. I have some experience installing decks at ground level but nothing with roofs. Of course we want to make the deck level but still maintain drainage on the roof. We had a contractor here yesterday but he quoted $22,500 which I would rather not pay if I can do it myself. Can someone give some suggestions on how to get started? The contractor mentioned sleepers to attach the joice to but I wouldn't know how many or how far apart to put them. Thanks for any suggestions.