Can't build second floor at top of stairs

[Fushizen]

I built my base on top of a plateau and when I place a staircase down and run to the top of it, it's not letting me place any other base components like floors or walls. What am I doing wrong? Some googling done but unable to find much on it.

[Fayte91]

make sure tyhere's support under it (the previous floor) if you want to do a balcony, make sure tto use the invisable floor

[Rossell]

I had to place the invisible flooring then I could place actual foundation. Its the only way it worked for me, so I guess its intended this way?

[Dr. Rockso]

I find it is super picky on where you are standing when trying to place floors and walls on upper floors. I had to get right up on the edge of the top of the stairs to get the floor to pop into the right place.

It also has to be over a tile that can be placed ie: can't be floating passed your territory border but not 100% sure if you actually need a tile there just the ability to place a tile there.

Pretty sure I have nothing underneath my second floor although I did put some pillars down for aesthetics.

[Fushizen]

I definitely tried making sure it the staircase was under an existing actual room (roof included) but I'll go back in and check to make sure I wasn't butting up against any boundaries. I also was unsuccessful at placing the invisible flooring, but I will try again. :)