My first post and I may as well jump in with both feet.
We just purchased a 2001 Kiwi 23b with known water damage. It is our first travel trailer. I have learned quite a bit already, but I know there is much more to discover.
Originally Posted by sawdust
...Yesterday while looking in a storage compartment I discovered that the vinyl flooring was just stapled down. I lifted the vinyl and found moisture between the vinyl and the plywood floor. ...
When they build most travel trailers early in the process the frame is provided with a "belly cloth"/plywood/composite floor and then that floor is covered with vinyl. (There are videos of the process.) The rest of the trailer (walls, cabinets, etc.) are installed upon that flooring.
The wooden floor is sealed between two layers of fairly impermeable material (the belly cloth and vinyl). Any water that gets between those layers basically gets sucked in and then has no place to evaporate out of the floor.
What that means to you is that once the moisture is there, it doesn't readily go away, but distributes in the flooring layers. Once it is wet enough the moisture will condense under the vinyl and lay on the belly cloth. That moist environment creates a bad environment for the floor structure.
Originally Posted by sawdust
...Could the moisture have gotten there from the damp air that this trailer has spent its life in up in Portland? I am looking for any advice on this matter.
In my limited experience it is unlikely that the floor has absorbed moisture from the air. The belly cloth creates a lower barrier. The vinyl floor creates the upper barrier.
Our 2001 Kiwi 23b had obvious roof issues in the front right corner. It also had floor issues in the back which were less obvious. The floor seemed basically solid, but the vinyl floor covering had obvious stains. That meant that there was more water damage. Unfortunately I was inexperienced and didn't recognize how bad it could be.
One of the things I have done is to open up every cabinet and storage space to cut out the vinyl flooring. I have even peeled back the tub lower paneling cover to cut the floor vinyl out and help moisture migrate out of the floor. My idea for removing the vinyl floor covering is that water can get between the vinyl and belly cloth unnoticed. For my lifestyle, the storage areas don't need fancy impermeable covering to hide water problems. By leaving the plywood floor exposed it will allow things to dry and also show any future leaks more readily. I'm certain that my 2001 will have future leaks.
I found that much of my rear area floor damage was because the well wells weren't properly fitted and sealed. Another area was the water hose inlets and the electrical cord cover. Outside lights have some history also. Remember that any leak, no matter how small, has basically no place to go once it is trapped between the belly cloth and vinyl. As the water enters it just continues to migrate to drier areas until it reaches saturation.
For my personal situation I am hoping that the moisture will leave my floor in the top vinyl removed openings I have provided before any more damage happens. Sorry I can't offer more. Good luck. vic