Open Stairwell?

Should give as a tool that can click a wall to designate it indoor/outdoor for such occasions then, just like placing a wallpaper.

It is bugged currently. My work around, which I used until I learned how to do it the "right" way, is to use the window shopping fencing from Get to Work. It's basically a really thin line that looks like it might just be a visual glitch. I use that to separate the stair opening from the rest of the opening. Then I can delete the flooring in the rest of the opening like normal.

Also, if you noticed whatever it was I figured out. It still caused the exterior molding to show inside in that corner in the top left.

To do an open stairwell like you intended to do, you have to close up the space using walls or fences so that the game recognizes it as a “room”. Do not worry about blocking the stairway, the bit where the stairs attach should automatically clear out. Using your second image as an example, there actually should have a segment of invisible fence at the stairway.

As for the molding showing inside, there is very little you can do about that, unfortunately. It is just how Build Mode is designed—the game always designates an inside and an outside automatically for each room, and sometimes deleting floors makes the game deem the part as exterior.

"Simmer_chiyen;c-17774895" wrote:
To do an open stairwell like you intended to do, you have to close up the space using walls or fences so that the game recognizes it as a “room”. Do not worry about blocking the stairway, the bit where the stairs attach should automatically clear out. Using your second image as an example, there actually should have a segment of invisible fence at the stairway.

As for the molding showing inside, there is very little you can do about that, unfortunately. It is just how Build Mode is designed—the game always designates an inside and an outside automatically for each room, and sometimes deleting floors makes the game deem the part as exterior.

This is how it's SUPPOSED to work; however, it's bugged right now, at least for me.

I am sorry to hear that. I have not had the time to test that out, so I would suggest you to submit a bug report on Answer HQ. It does not appear to have any post related to this one, but there is another unsolved routing bug regarding staircase on there.