Legal Question in Real Estate Law in California

To find your legal description, try looking at the deed you were given when you purchased the property, or go to the tax assessor's office (some have parcel viewers online) and use the APN (assessor's parcel number) to locate a legal description.

There is no single state-wide statutory definition. Here's a typical one, taken from the San Diego County zoning ordinance, which seems to be as good as any other:

"Two dwelling units placed side-by-side, which may be attached or detached, both

of which are on a lot or building site which is unoccupied by any other dwelling unit."

There is some discussion of the legal meaning of "duplex" in the case Calderone v. Post (1982) published at 134 Cal.App.3d 1008, but I think the San Diego zoning ordinance definition is pretty clear and probably most lawyers and judges would agree with it. The major problem with the San Diego definition would be the "placed side-by-side" part, which I think needs to be interpreted to include "or one on top of the other."

I might add that units placed one on top of the other might be thought of as 'flats" rather than as a duplex, in which case the San Diego County definition needs no additional language.