Looking for a make floor script

Ok I have a thought for a build but I need a script that would allow me to make a wall interact with the avatar as if it is a floor? So I could have a building that in one room the floor is actually the floor, but then in the next room the wall is actually the floor for that room. So what I'm trying to fine I guess is a way to have a script that would allow me to rotate the down aspect of gravity for that room.