So this has happened to me a couple of times since playing the DayZ Standalone now. Once in awhile, I will fall through the floor of a house and become unable to escape. Everything below the house goes see-through and it makes the game look very strange. To other players, it looks like you are standing on the floor normally.
I have managed to escape this glitch TWICE now. What you need to do it, stand in the very corner of the house and vault/jump through he wall AND log-out. You need to make sure you log-out while your character is in the air. It can take a few tries, but it does work!
Hopefully this helps a few others who have also been stuck in the floor.