All of these suggestions are extremely helpful. Thank you for the responses.

Possibly I am expecting too much of the program or need to start over.

The current design has 12' walls built on the ground. I want to add, on top of the ground (not underground), the 24"-36" subfloor with the house then sitting on top of the subfloor. Thus, the height would be 14'-15'. This way I can correctly render the front/back porch and the step-up from the garage into the house.

I could be using the wrong terminology, so apologies if I confused the help request.

Thanks again for any insights/workarounds.