additing a second floor on a garage seperate from the house

[Dave Pitman]

If you develop the garage in it's own plan file, you won't run into the issues like the 2nd floor thing. It is possible to have them both in the same file as Scott suggests, but anything "auto built" in one building will extend to all the buildings in that file. This can become a real problem for new users.

A symbol is a 3d representation of the model. you use it to show both the footprint, and a 3d representation in camera views. If you modify the exterior of the garage after you have made a symbol of it, it would have to be made into a symbol again to be a true representation. Converting a building into a symbol is quick and easy.

For construction document floor plans, it is no problem to send the floor plan from 2 (or more) plan files to a common layout page.