Hi MMD and John, In my limited experience, the doorways are more
expendable than the piano. I have an Ampico upright that I have had
in and out of six houses in the last 40+ years, including the basement
in two of those houses.
The first time, I hired professional movers and they had to stand the
piano on end to get it around a corner. A year later when it came back
out, by pure chance, I was lucky enough to have the same moving crew.
So they knew just what to do.
In several cases, I had to dismantle the doorways, and in one case
I even had to take out some of the dry-wall and a stud. I put the stud
back in place with lag screws because I knew I would have to repeat the
process when the piano came back out.
A doorway comes apart very easily when attacked with a measure of care,
a thin, wide, putty knife and a small hammer. Start with the molding,
and when that is off, the door frame can come out. Be careful and you
won't damage or split any of the boards.