Ummmmm, What year Casita
? Cause I have never seen a Casita's with plywood floors, they are encased in glass (there is a name for it, but I can't remember what they actually call it).
That is not to say it couldn't get a sloppy floor, but find it weird that you say rivet's poking thru! Underneath?
Can you take pic's? Wasn't the Casita
completely fiberglass underneath?
I am sorry, I am not much help. But have to question cause I have never seen a Casita
that wasn't fiberglass underneath. Hopefully someone will be able to help you.........
Oh and glad you joined us! Welcome!