Export your model to your Architecture drawing software

DXF

 * DXF-Exporter : ver.1.25 can export 2D and 3D mesh and curve objects to DXF-r12 format. (09.2008 migius at blenderartists.org)


 * (obsolete) DXF export function is built-in Blender, not a python script. It exports all the blend file. So if you want to export only a part, you must delete all the object you don't want to export before. Only simple meshes are stored in DXF files. Convert NURBS, Curves, modifiers to Mesh (Alt-C). Apply Size and Rotation too (Ctrl-A).

Allplan

 * DXF is the only format between Blender and Allplan this way. In Allplan, before importing, click on "options" button and select "explode macros". You can also choose here wether you want to import the model to 2D or 3D.