On the Vertical Definition tab of the Door: definition dialog, you can specify the location of a door with respect to a wall or a plane.
Define the vertical location of the door:
- Level with respect to wall - when positioning a door opening along the wall height (the Z coordinate), there are 2 possibilities (the default is 0.0 from the lower wall level)
- the opening is located with respect to the lower wall level and measured to the lower part of the door 
- the opening is located with respect to the lower wall level and measured to the upper part of the door
- Level with respect to plane - when positioning a door opening with respect to a plane (for example, the floor rather than the story level), select the plane from the list, and then specify parameters
- Reference edge of a door with respect to the upper or lower level
- Offset from the lower or upper story level.