[Bay Area] Should I request permits to even uneven floors?

[Sonia Wu]

Hi BiggerPockets community!

This is a fairly specific problem. Hopefully someone here can help us out! We recently purchased an old Victorian house in Bay Area, built in 1901. It is a 2 bedrooms and 1 bath with basement. We believe the back of the house is an addition, as it is not built on top of the basement, and the floor has become uneven over time. We want to even the floor up to the same level as main house and are unsure if we should request a permit for it. 

There is no online permit records for this addition. Makes sense, since San Francisco only tracks permits from 1980+, whereas this addition was likely added before 1950s (based on very old pictures). I can't determine if it was permitted work. On one hand, the appraisal and inspection both considers this as part of the official living size of the property. The bathroom and laundry hook are also built there, which I believe should have a plumbing permit. However, it seems to be built with less solid material than the main house and has very obvious tilt (two inches). Are we liable to rebuilt if it is an unpermitted addition or should it be the previous owners? The previous owners held the house for a short amount of time as an investment property. They don't know much about it, didn't do any renovations, so we didn't ask about permits. I do want to do it by the code, but am worried requesting a permit to even the floor will open a can of worms. I am also unsure about legal obligations.

I have heard some conflicting ideas about this, hopefully the BiggerPockets community can provide some insights. Thank you!