There are a couple of things you need to know about floors, walls, and segments:
1. If you want to paint only the floors or walls, you need to click on Segments on the tool bar, and then click on either "Paint Only Walls" or "Paint Only Floors". This will allow you to either paint or remove just the wall or floor.
2. You cannot have a wall from one segment and a floor from a different segment in the same tile. FPSC just doesn't allow this to happen.
3. You CAN use a floor entity and a wall segment, or a wall entity and a floor segment, or a floor entity and a wall entity, in the same tile.
Priest of the Church of Joe Wood