Why do I get out of range errors when importing DXF floor plans?

There are 3 usual reasons for this:

1. The units are incorrectly selected. For example, the CAD drawing may have been defined in millimetres and you have selected metres as the units. So when DesignBuilder tries to read the floor plan everything is 1000x too big and meters become kilometres! The DesignBuilder modeller has a range of several hundred metres.
2. There is some non-geometric garbage in the DXF file for example the title block. In this case, you should clean up the drawing before exporting to DXF.
3. The DXF file is open on another CAD application. You will need to close the application session that is running the DXF file. 

See also: 

Importing 2D CAD data