block vive teleport between two floor

hi guys,
i’m working on a vive project, in a 2 floor flat.
i’m about to find a solution for teleportation in stairs, but it’s not so good.
anyway i’ have a problem to block some part in the navmesh.
i explain myself :
in the forst floor everything is ok i put some navmodifier volume on the outdoor wall, but when i’m inside the flat and i point the teleport over my head in direction of the ceiling it’s teleport me on the second floor.
In the same way in some case in the second floor when i block some wall the teleport is going in the first floor.
i want to create something to block the teleport between the two floor in any direction.
i don’t know if you understand me, it’s a little bit strange and my english is not so good.
if you have some tips or advice. i would be happy to ear from you.
than’ks a lot.