Tornados don't tear out the floor. Not and leave the rest of the house. People do.
Guy across the street from my MIL used to keep round bales in the old singlewide across the street. The roof was still on, it kept them dry.
I'm pretty sure half a house qualifies as a barn in my area. I have seen horses who lived in everything from old boxcars to a partially demolished trailer home. They usually try not to have that step up though, otherwise some horses won't use it.