[declan]

Framing requirements have become far, far stricter. Here's one construction project currently being framed on the SF peninsula: https://goo.gl/photos/hdDmcqWkEuQenvku9

It's a one-story room with a 9' ceiling height. The structural engineer specified two massive Simpson Strong-Walls, side by side. There was barely any room for the window, which had to be askew as a result. A local architect tells me the requirements were far less onerous even a decade ago.

Also foundation requirements have increased as well. You may be on a flat lot with no history of problems based on a soils analysis, but end up having to drill piers anyway. Just in case. Your municipality wants them. Which will likely increase foundation costs by tens of thousands of dollars--so much for affordable SF bay area housing!

I know one fellow building a new home on the SF peninsula who spent $500,000 to pour a roughly 1,000 sq. ft basement. (Small lot, not much outdoor space, so he was determined to have a place for his kids to play in.)