Use the Ceiling tool to create a ceiling in a reflected ceiling plan view.
 Build panel
Build panel
 (Ceiling).
 (Ceiling). 
Use walls as ceiling boundaries
By default, the Automatic Ceiling tool is active. When you click inside walls that form a closed loop, the tool places a ceiling within those boundaries. It ignores room separator lines.
Sketch ceiling boundaries
 Ceiling panel
Ceiling panel
 (Sketch Ceiling).
 (Sketch Ceiling). 
	 
 (Finish Edit Mode).
 (Finish Edit Mode). 
		