How toWaterproof a deck - make a roof for patio at same time

I have a 17x40 second-story elevated deck I’m building and am looking for a product or a method which will allow me to waterproof the top side so the bottom patio side stays dry. Any ideas? I’ve heard talk of “cementitious coating” but don’t know anything more - it’s trade name etc. Any help would be appreciated.

Wood? Concrete?

torchdown makes a good roof/deck.




This is a product that we install on walking decks. We glue it down to 1/4 inch “cdx” plywood. It comes in several colors. This makes a really nice looking deck.


The reason that I ask is because polyureas can go direct-to-deck, self adhere, self flash, be applied in an anti-skid, comes in many colors, and will be leak-free as long or longer than any applied sheet goods at comparable thicknesses.

Torched down modified bitumen does not make for a good walkable deck without pavers or some other kind of surface protection, as it is soft and easy to scar/damage with foot traffic.