Problem with primitives

[TheHunter]

Hello, I have a problem with my custom story, what happens is that I was editing it (before that I put a hallway outside the room from the start but I did not like and put the following):
I put stairs and a floor (below the height at -4) With walls of course. and emerged the problem when starting the amnesia and between my custom and looked down the hall, the stairs were not. Down the hall saw the tables and candles but not the walls or the floor! Please help me with this problem! Sorry if I did not understand much, for my bad English or because evil has explain.