Aye, it was really weird. The process went something like this:
Evict family to clipboard
Change lot type initiated
"Some items on this lot are not meant for community lots, and will be deleted. Proceed?"
Cancel lot type change
Put everything in family inventory except for sculpting station (a sculpture had been started); 20 racks of nectar; shuffleboard game. Oh, and ceiling lights.
Change lot type initiated
"Some items on this lot are not meant for community lots, and will be deleted. Proceed?"
Cancel lot type change
Scrap sculpture, put station in inventory
Put racks of nectar in inventory
Get annoyed when shuffleboard game can't go into inventory.
Curse a bit, sell the shuffleboard
Change lot type initiated
Success!
Reinstate family to household
Shove doors, windows, and arches into inventory
Tear down walls
Rebuild house bit by bit, putting in a foundation
Successfully get the stairs set up so foundation house will go into basement
Put everything back
Man, that was an exhausting 3 hours. And the only major renovation besides the foundation was ditching the garage to give my money tree grove a better place to flourish. (This was good, I maxed gardening profession in 3 days with only 2 harvests totalling about 260 money bags). However, I still can't fix the pathing issue of trying to potty train toddlers, so the adult wanders outside, out the front gate, and waits for the kid to chase them down.
Enough off topic, though