MathewM

FYI - Never found a good solution. Lowering the height of the stem wall for this stairwell room fixes it. It's not correct, but it renders correctly. Could not find a way for the floor above to attach as a ledger rather than above the wall.

Not a bad theory. Only thing is, before the stairwell, this was just an existing room, and its structure was fine. So I carved the stairwell out from that room. I think I will try deleting and rebuilding the stairwell. If the failure occurs when I hit "Auto stairwell" which kills the cieling and marks the room above as "open below" then that must be the culprit.

I suspect the fact that the stairwell has no ceiling above is a factor. Although that doesn’t really present a solution either.

I am a bit stumped on an issue with a stairwell adjacent to an exterior ICF wall. Although it's not really exterior since there is a garage attached on the other side of it. I suspect that is part of the problem. If I break the wall of the stairwell, so that it is no longer a separate room, everything is good, and the room structure is correct with the floor above hung on a ledger attached to the stem wall: If I complete the wall and create a stairwell room, the stem wall moves under the floor above and pushes the footing for the ICF wall down just where the stairwell is: You can see the reason when looking at the structure for the stairwell: Note that it is doing this even though I have "Hang floor platform above on wall" and "Subflooring to wall interior" checked for the ICF wall. Note that if I move a wall to break the garage on the right side of that wall, that also fixes things. Note also that there are other rooms above and below the stairwell and they do not cause this problem. Only the stairwell. Any ideas? Thanks!