I'm talking a wild, cheaty building full of CFE, weird roof concoctions and 2 hours worth of "how do I get the lighting in that spot to not be borked now". Now I'm realizing I'll need a foundation under all of that.

Is there any way to do this to an existing house?
I really can't turn the first floor into a foundation and then move everything up one floor, it will mess everything up so much that I might as well rebuild it all. Workarounds like that sadly won't do. I really somehow need the game to consider a new, extra floor the ground level, and then the former floor 1 to be floor 2, and so on.

I would've sworn you could do this with GridAdjuster, or did I dream that? I can find all sorts of tutorials on fancy things, but I can't figure out how to just squeeze in an extra floor for a foundation at the bottom.

Please help, I might throw my laptop out the window if I have to rebuild this one...

Yes, I believe this can be done, but let me do a bit of tinkerin and I'll come back shortly. I know I've done the reverse, takin the foundation out, as well as turnin foundation into walls .. so I don't see where this should be an issue, but I will check and get back with ya ... unless someone beats me to it :D

I believed wrong

There may be a way to do it, as I seemed to get some things done .. however it was only after I deleted walls and replaced them ... and with the house you have that's all ready full of CFE and you're not wantin to move things .. You can come down, but it seems you can't go up.. at least not without a lot of work and changing .. and even then it still may not work correctly .. sorry to give false hope

You cannot just move an entire lot up and add another layer underneath. You can use Moo's ConvertiWall to change the lowest build walls to foundation walls. But of course, it will be at whatever wall height the first level of your build is at. If you try and use grid adjuster to lower it, then all of your levels above will be wonky.