Creating Basement after Main Floor is Built

[ChiefUserChelsea]

I have created the ground/main level of a home that I am working in some renovations on, but need to add stairs to the basement. Every time I attempt to add the stairs, they will only go up to a second floor because I have not added a basement. I am attempting to add the basement, but the software does not seem to allow me to add a level below, as opposed to adding a level above. In an attempt to fix this, I opened another Working Plan View with the simple dimensions of the basement, thinking that I could then combine the Plan Views within the same project. I can not figure out how to do that either. How do I add the basement without having to start from scratch?

[Chopsaw]

This is only a problem in real life.  But in chief you are doing it exactly right.  Just use the "Build Foundation..." tool rather than the "Build New Floor..."  tool.  It is just a little lower down in the same drop down.

[ChiefUserChelsea]

Perfect! Thank you so much!