Autodesk has finally fixed a major wall cleanup issue between mirrored xreferenced drawings in AutoCAD Architecture!
Cleanup between overlapping walls in different xreferenced drawings was introduced several releases ago in AutoCAD Architecture (Architectural Desktop name at that time). As they continued to improve the feature, walls still had problems cleaning up properly when the xref was mirrored. If an existing xref was copied and mirrored, the mirrored version would have gaps in similar locations as the first instance of the xref. If an xref was brought in and mirrored (without being a copy of another xref), then the xref would not cleanup at all. Either way, walls in mirrored xrefs would not cleanup correctly with walls in other xrefs.
In AutoCAD Architecture 2010, wall cleanups now clean up correctly when the xref is mirrored, regardless of whether the xref has been copied or not.
This feature is very important for those users working with apartments, hotels, or other situations where the same layout is used repeatedly in the building. In those situations, a room or apartment file is created and xreferenced into the host file multiple times or copied multiple times in the host file. There will almost always be a need for mirrored units in those situations. This is a huge and beneficial item for users with those needs.
If you are not familiar with setting up this feature, go into the drawing that will be xreferenced and open the Style Manager from the Manage tab. Expand the Architectural Objects category, then expand Wall Cleanup Group Definitions. Highlight the name of the cleanup group for which you want to enable this capability. In the right pane, place a checkmark next to “Allow Wall Cleanup between host and xref drawings”. Pick the OK button to exit out of the dialog boxes. This will need to be done in each drawing that contains walls that you want to xref into another drawing and have walls clean up. This can also be set up the template if you always desire walls to clean up between xrefs.