@funkeeferret, I'm still learning the restrictions of platforms. That and custom depth foundations, where you sink the ground below where you want to build the house, place the foundation, then use the raise ground tool to further bury it so that is resembles the effect I think you were going for. I've seen it done, but it seems to be very finicky.
As for getting "x" far into a build and finding a crucial error, THAT is why I bought myself some graph paper. Next time that happens I will carefully transfer the measurements to the graph paper so that I'm not starting from scratch ..... and he hits his head as he has an epiphany... CUSTOM BLUEPRINTS!!!!! Just save each room as a blueprint, transfer the footprint of the building to the graph paper (because the blueprint tool won't build the basement) and put each room back into place complete with furnishings, wallpapers, etc!!!!
I hadn't discovered custom blueprints when I'd come up with the graph paper solution. The blueprint solution is so elegantly simple. Rebuilding my childhood home project, 25 Cute St, will be a breeze this way. Coincidentally, I'm rebuilding it to add the missing basement.
And you aren't "hogging up" my thread, you're participating!