My local RV repair shop told me that water damage keeps him in business. I have, through the years and several rigs, experienced dry rot in walls, floors and cieling. There is no magic cure and if you have to pay someone to fix it can be quite cosly. In one travel trailer, I was able to cut out the damage in the bathroom floor and patch it with exterior plywood and then used peel & stick vinyl tiles to finish it off. Was a lot of work but kept the rig for 4 more years with no further complications. Best of luck.