Hi there,

Glad to know that you upgraded to V20

Regarding you question:

Actually, there are different options, depending of your necessities and preferences.

1 - You can create 2 Punch files: one for the original house and another file for the original house + the addition. This option will be very useful if you need to create "before and after" plans, elevations, etc.
2 - You can create 3 Punch files: one for the original house, a second one for the addition, and a third file for the original house + the addition. This option will be very useful if you need to compare materials and costs for each option using the Estimator Power Tool.
3 - Your new Premium V20 program allows 6 floors. Notice that the floors are just locations in the space, so you can set two or more levels as different floors but with the same elevation. Therefore, you can set each stage as a different floor. You can print / visualize each floor separately, but at also, if you wish, you can visualize the entire project.

Hope this helps.

You are welcome!

Punch, as any program, has a learning curve. The best way to learn the program, IMO, is practice + practice + practice => Read and follow the manual (this is important), see the videos => try to create elements not related with your project, so you will become familiar with the commands and how to develop the different components.
Of course, let us know if you have additional questions.
You will find free tutorials in my Website and Facebook page
If you are interested, this is the link for the V20 eBook for Windows. Also see a link to my eBooks page below, in my signature.

Hope this helps.