Is the wall of the staircase either inside or outside?
Interior wall, non-load bearing wall, elevator shaft for the load-bearing walls
Can be identified as the interior wall. Exterior wall, is bearing wall.
Stairs between the walls of the wall or the wall depends on the location of the wall, the general situation of the building outside the wall called the external wall, otherwise called the wall.
As you refer to, it should be the interior wall!
