new developments are in 3000 sq ft lots and have 2400-2600 sq ft built area
Likewise, that initial 20% by area (2000 of 10,000sqft) structure dimension ratio sounds made up.
Re newer developments, here is an example: https://www.lennar.com/new-homes/california/san-francisco-ba... : plan 5, icona. Three stories, 2300 sq ft built area approximately. 1.2ish million.
On a related note, I browsed that random google link and clicked on ‘home automation’..basically it’s an Amazon home. Alexa would run your household. I am not sure if that’s a good thing or a bad thing.
All Bay Area cities have to follow mandatory orders for building quotas from a Bay Area organization called ABAG
First hand accounts re older properties
How about one example of any parcel with a residence footprint taking 80% of the parcel area?
As or that Lennar development, you are totally ignoring common area (exclusive and nonexclusive use).