When an element is no longer associated with a work plane, the element is free to move irrespective of a work plane. On the Properties palette, its Work Plane parameter value is <not associated>.
Examples of work plane-based elements include solid geometry in the Family Editor and extruded roofs in a project.
To dissociate an element from a work plane
If the Dissociate button displays as gray, the element is not currently associated with a work plane, or it is not a work plane-based element. (For example, it may be a face-based element.)
To reassociate an element with a work plane, use the Edit Work Plane tool to specify a new work plane.