It would be nice if there was standardization for such things. No doubt most counties will have on file somewhere blueprints and drawings that were submitted for building permits but most likely haven't been digitalized. I'd hope that newer homes could have their blueprints submitted digitally by the architects but I suspect most places are still using paper centric processes.
About twenty years ago I worked for a big box store's corporate headquarters. One of my tasks was to add new stores to MapBlast so they would show up on the "Find a store" section of our website. Problem was that often stores were built in new sections of rapidly growing sprawl so the streets weren't in MapBlast yet. I'd have to make educated guesses as where to put the store on the map. Sometimes I could call the store and get some help that way but for our international stores, that was difficult because of the language barrier. We knew that there was some department somewhere in the company that had detailed drawings of each store, including precise location coordinates but the company was so large, we had no clue where to even begin to find that department.
This can detect rooms as polygons, doors/windows as line segments and bounding boxes around objects (e.g. cabinets, sinks etc. indicated on floorplans).
