I have a house with an add on that has a roof with rolled roofing. The roof has a slight slope. There is a door from the second story leading out to the roof for the first story. I want to place a deck on the roof. The structure is more than sufficient. What I am worrried about is ruiing the non-leaking roof. I figure that if I just lay boards on the roof it will eventually wear through and leak and then I have to tear up the deck. Is there a better way??