I've been playing for a while now but have never encountered this situation. Has anyone come up against the "covered by floor tile" message when trying to add rooms/walls? I just moved into a new place. First I was going to make a room out of the garage. I wanted to split the garage into 2 rooms but when I went to put in a wall I got the "covered by floor tile" message. I tried various things: deleted what was there, leveled the terrain, flattened the lot, got rid of the existing walls to put up new ones, deleted the whole garage including roof,....didn't work. I then abandoned the garage and decided to put a room on the other side of the house. I got the same "covered by floor tile" message on that side of the house too.
Does anyone know how to get by this "covered by floor tile" situation?