Broken stairs!

I never have that problem but I think it's game mechanics. You have to build the basement and put the stairs in. THEN, you may raise the foundations.

@mikes1987

I agree with @Chazzzy , not sure exactly what you're problem is. My guess is trying to remove the floor/ceiling on the stairs side after raising the foundation to go to the basement (first underground level).

This has nothing to do with updates or a broken game or even mods. It's the build mode mechanics. Which can be frustrating at times, I know. ;) My guess is what @Camkat said, either remove the ceiling/floor first before raising the main level, and/or putting in the stairs.

I'll give it a try, maybe I can help. I suppose I could make a video, but I'll just take screenshots for now.

It's because you deleted that floor tile.

@mikes1987

I basically did the same thing you did, except that I made the part for the two levels a separate room first then removed the ceiling and floor. Fit the stairs in. Then raised the foundation by 1 full square up. I tried redoing the stairs, but from basement level, it only goes to ground level, not raised foundation level.

So to get the ground level top of the basement stairs to the raised foundation floor level, I had to make a 3 square room that matched grounds level, then put stairs there that goes from the basement stairs to the raised floor. After that I put walls back in and made a fence/gate.

https://i.imgur.com/l9yB3U6.jpg

It actually technically turns into 3 levels if you raise the foundation. Although you can directly connect stairs from the basement to the raised foundation level, you can't do that if you want an open ceiling-floor next to the stairs. Without making a second set of stairs.

https://i.imgur.com/kmkLuZg.png

Another way I tried, that's actually easier and less "messy", is raise the basement level up by one full square. Then build the main floor on top.
Then do the same as before for removing ceiling/floor in a room on part of it as a separate room.
Put the stairs in.

Only thing is, this way you have dirt around the raised foundation instead of an actual raised foundation.

https://i.imgur.com/XZZE9d1.png
https://i.imgur.com/f3JQx05.png
https://i.imgur.com/pekyoGM.png

(I made sure a door and stairs to outside worked, which it did.)

Build mode has some crazy mechanics sometimes and they can be a headache. :/ Especially basements. My guess is it's because basements were added later and then terrain tools even later than that. Now we're adding stair cases that can switch back... It's kind of a mess but it's not so bad once you learn the limitations.

Thanks @Admiral8Q for the screen shots.

All that you have to do is go to the basement level and use the vertical arrows to lower the basement until the ground levels out. The arrows I am talking about are the same arrows the op used to raise the foundation on the first level. In the basement level use the arrows to lower the room.