Well the new floor is now in the camper and everything is sealed back up. Took a carpenter friend and I all weekend but it is now done and much better than new. This was completely caused by a design defect. Plastic side walls of slide stop about 1-1/2" from the bottom of the slide. Water runs down the slide and wicks into the black darco fabric. On each side of the slide, there was even a black sponge screwed into the edge of the OSB floor. The could not have built any better of a wick if they tried. Once the water is inside the darco it does a great job of holding the water in up against the osb floor. The only thing holding it all together was the darco fabric.
Having a traditional stick and tin TT made taking it all apart surprisingly simple. We took the bottom three siding panels off and exposed the studs and then screwed a 14' long 2x4 accross the exposed studs and jacked the slide up so that it no longer required the floor to hold it all up. The built the slide with a double bottom sill. The plywood floor was stapled to the bottom sill. The two sill plates were screwed together from the top. Unscrew the two sill plates and the floor came right out. We replaced both top and bottom sill plate on the sides. and the bottom plate on the outside wall. No water damage to studs or insulation. The long wall bottom sill plate was actually okay as well but it was easier just to replace it than try to reuse.
We used 23/32" 7 ply AC plywood for the new floor. We put the seam under a dinette bench and glued and screwed a splice plate in under the dinette bench. The perimeter of the floor is wrapped with the black EPDM roofing tape from Lowes. We used RFP for the bottom, the sides now have L-shaped vinyl flashing to cover everthing up. It is all glued and screwed. Floor is nice and stiff now.
Who ever owned this before me knew they had a problem but thought the water was coming in from above. Having the walls opened up, it has clearly never leaked anywhere but at the edge of the floor. The worst part of the whole deal was all the caulk they have crammed in at the corner trim posts. Getting all that scraped and cleaned off was extremely tedious. Scratch the siding a bit and rubbed a little paint off in places trying to get it clean for the new butyl tape.
To others that have to deal with this, it looks more intimidating than it really is. Read thru JBarca's thread, look at some youtube videos, and get started. If you can do any kind of home carpentry work, it is not complicated.
If I had to do this on a camper with fiberglass laminated side walls, it would be a whole diffent story.
I took some pictures along the way and need to set up a photobucket account so I can post them. Nothing as extensive as JBarca's log. JBarca your thread was instrumental in me having an understanding of how this all came apart and went back together before I started so I did not have to go thru the learning curve. I thank you sincerely for that.
