How do I delete this floor above my stairs in a basement?

"coldplay2233;c-18300979" wrote:

"LeGardePourpre;c-18300923" wrote:
Put a fence right at the top of the stairs, it will split the room into 2 and the fence will be invisible.
Then select the room and remove the floor.

This worked, thank you !

Just as a side note, sometimes the game gets picky about fences going across stairs and will decide that sims can't go through them, so when I need to do this, I always use the "caution tape" fence because sims can step over it.