I just had a sun room (12' x 20') built on a portion of my deck to add more usable living space and now I want to finish up the floor since this is now an indoor space. The deck is the standard treated 5/4 lumber and, of course, it isn't perfectly flat but not bad and it has the usual gaps between the boards. The deck surface is about 2 inches below the patio door threashold so I have room to build up the floor some. I would like to use DuPont Real Touch Elite interlocking laminate on the floor. It is supposed to be very water resistant, is glueless and has the foam underlayment already on the back. It is about 7/16inch thick. The walls sit in tracks that are sealed to the deck and have an L flange on the inside that the floor would lap over.Under the deck is a walk out basement patio area that I also plan to enclose in the future but is open now.
My question is about what to put under the flooring.
Do I need a barrier like felt paper?
Should I use an underlayment like 1/4 inch or 7/16 inch OSB?
