How to un-join complex shapes (more than 20 lines)?

I have several complicated shapes (building outlines) that I need to join in
order to fill the shapes. I need to know how to return the 'shape' back to
it component lines. Drawing intersecting lines for 20+ vertices is not an
optimal solution, even if I didn't have to repeat it for different buildings
over and over and over.

I use my Delphi applications and drawings, including automated scripts to create designs with hundreds of shapes on a page with all the connectors that works in seconds.