I bought the Universal Cottage plans a few months back, and in scouring old posts, noticed a comment that if one uses I-beams, one can position interior walls wherever. This was not news to me. However, the comment also indicated that the stairs may NOT be moved, even if one uses I-beams. Why is this? If the engineered I-beams are carrying the loads to the outside walls, what weight-bearing purpose do the stairs serve?
I'm probably missing something embarrassingly obvious here (wouldn't be the first time).
Thanks in advance!
The stairs can be moved where ever you want. It will, of course, involve changing the stair opening in the 2nd floor framing of the I-joists (and in the main floor if you have a basement). That opening can be slid forward or back and moved from one side to the other without structural consequences.
Note: I'm assuming you will use the "U" shaped stairs in the plans that has a rectangular opening. You can get into having to have a post when you do an "L" shaped stair. But this too can be relocated when the stair needs to move.