Sub deck water proofing?

I have installed decks on flat roof garages. The decks were built in 4 sections, that way any one section could be pulled up for a repair beneath. What is the composite material on the roof now, this makes a lot of difference as to what you can apply. Also, a couple of pictures of the deck and roof would be helpful.

-- Methods are many,Principles are few.Methods change often,Principles never do.

Ok, in the mean time, look at this product. Flat roofs are notorious for ponding water. Even on well designed roofs, eventually you will encounter some minimal ponding. I have used this product over both old rolled out roof material and badly laid and sealed rubber membrane roofs with good success. Take a look, read it carefully to make sure this is the product your looking for.
http://www.tkocoatings.com/roof-kote.html

-- Methods are many,Principles are few.Methods change often,Principles never do.

I think UL has it covered pretty well

-- a-1contractor.com

I checked the product link and it looks like the right stuff. We didn’t build the deck.. previous owner did, and like many of their “fix ups” it wasn’t done with the thought of longevity at all. We intend on rebuilding the garage and just putting a new kitchen/living space over it…
Anyway, thanks for the advice. I’ve not pulled up any boards yet to get a better look, so can only see between them right now. Perhaps a pic or two this weekend if I get the chance.

-- I was a knowitall... until I bought a house