I see what I did wrong. I didnt want to see the siding in the stair opening so I stoped the slab short of the inside. Then drew another slab with the same material as the interior wall. But then you can see the two slabs on the floor plan. And I changed the outline pen to a white color so it didnt show. I gues I will just draw a white line over the line between the slabs.
Sorry for bothering everyone
Brian