Ah, so that's how the pros build architectural models!

Here's a nice video of how Sweet Onion Creations uses a 3d printer for the interior of a house model. They still fell back to basswood, wood, and metal for the final structure. They were making a physical model from the winner of a SketchUp house design contest.

http://sketchupdate.blogspot.com/2009/12/making-of-sweet-physical-model.html

Lots of the model making looked awfully similar to building structures for my model railroad, except they've got much nicer tools. Printing the entire interior in one fell swoop was mighty impressive!