Stein means Stone, "um" in this context stands for "by" or "after". The song describes how the singer walls his beloved in so she won't be able to leave him. Pretty macabre.
I have plans, big plans; I'm building you a house; every stone is one tear, and you'll never move out again.
Yes I'm building you a little house, It has no window, no door, it will be dark inside, No light comes through .*
Yes, I'm getting you… read more