You must log in or register to comment.
I’ve fixed it! The bottom of the door is attached to a quarter circle panel, which slides into a slot under the floor when the door is closed, and provides a temporary floor when the door is open.
How does this even happen?
I’ve seen this kind of door in a place where the space was originally unfinished attic (with only ladder access), and the door was cut through the wall and the space finished later.