Painted surfaces will report the incorrect surface area if no material is assigned to the base geometry. This is super dangerous because few users are aware of this issue and there is no warning that it occurs. This is my post of the subject https://forums.autodesk.com/t5/revit-architecture-forum/paint-applied-in-family-editor-shows-incorre...
Us unwitting users should not be left out in these dangerous waters! This is my idea:
Please alert users with a nag screen if painting geometry that has no material applied to the main geometry. It should say something like, "Warning, area of this painted geometry will reports an incorrect value in schedules because there is no material applied to the base geometry", then include a "Don't show me this again", and an info button that explains the issue in more detail.
This this nag screen will at LEAST make users aware of the issue and they won't spend days trying to fix it, or worse yet, never knowing about it at all and then send out embarrassingly incorrect drawings, or worse still, the builder also not noticing that your drawings are incorrect.
