Xiste -- Thank you for the recommendation. As a newbie to this program, I've tried with my limited knowledge to follow your recommendation with no success. Would it be better to send/post the file to 'see' what the house design is and then add the numbers in the boxes where the measurements should go?

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 ...

Tried adding a negative number -- nothing seems to happen. Is it Level 0? Any procedural steps would be appreciated.

Giant thanks!

Amazing design program! Thank you SH3D!

Amateur enthusiast designing our single story dream home. Realized I need to add a 24" - 36" subfloor UNDER the existing single-story design.

Can you point me toward or list the procedural steps to get this done? I tried adding levels, but it appears those ...