I am in the plannning stages of building a woodworking shop. I plan to build it 24 foot by 40 foot. I will be building it into a hill where one end of the roof would be ground level. This would allow the roof to be used as a deck if I put a flat roof on the building. Should I or shouldn't I build a flat roof? What materials are out there to build a flat roof that allows it to be used for a deck. Whatever material I use I want it to be the floor of the deck. I don't want to contruct a wooden deck on top of the roof. For example, if I put a rubber roof on I want the rubber to be the floor of the deck. Anybody have any ideas or names of companies that they know of that have a good product for this type of roof? Or should I not even consider a flat roof?