Re: Stairs issue
A pic would be helpful here. But what is above the floor you are trying to place the stairs on? Build mode error message can be misleading at times as to why something won't work. It could be something above blocking the stairs. It could be other things too, like a platform.
One thing you can do is just create a square room, put the stairs in, and then raise the foundation using the big arrow in the center of the room. Then complete the rest of your build with the stairs already in place.
Hope this helps.
