Building 2nd floor deck12X20, overhangs 1st floor front porch of same size, need 1st floor free from water. ??How do I build this?:confused:
Google "waterproof decking system". There are several ways to assure that no water gets through to the lower level: interlocking aluminum decking "boards", membrane roofs, under decking drainage systems, etc.
A walkable, waterproof, membrane decking system is the way to go. I installed one of these systems on the porches of my five story apartment building. They come in a 72 or 75 inch roll or 60 mill or 72 mill thickness. They are a glue down, heat weldable system. If you have installed vinyl floor you can install one of these systems. The membrane is not cheap and the heat gun will cost about $400 by itself but they do work. You glue down the membrane just like a vinyl floor but using the specialized heat gun to weld the seams together. The even have termination bars that are heat weldable. They are very resistant to tears of holes but should one happen you can heat weld a patch over the hole that is virtually invisible. My seams are actually hard to find. There are several different brands and they all install the same way. There are even on-line videos that will show you how to do it.