Highland Park - ADU on R1 zone with duplex built in 1924

[Christian Dulu]

Hi everyone,

I just recently purchased a duplex in Highland Park, and will be owner-occupying one of the units. I learned that out back, the previous owner had some sort of unit that was torn down in the last year or so, and a shed erected in its place. However, where the unit used to be, there is a concrete slab, with electric, water and sewage hookups. I also discovered there was a third electric meter which had a 1/2 address attached to it, and confirmed by LADWP. 

I assume that the previous owner had to tear down his unit because it was unpermitted, but it seems like the basic infrastructure is there to support an ADU. However, I'm not sure whether I would be able to legally build an ADU out back, because from what I've read, you can only build an ADU on land that is zoned R1, with a Single Family Home. I assume that the duplex was grandfathered into the current zone, as it was built in 1924.

I feel my situation is some sort of edge case, so I'm wondering if anyone has any insight or tips on whether this is possible, or even somewhere I can start. My sticking point is nowhere in the regulations does it mention anything about building an ADU on an R1-1 zone with an existing duplex. Could my duplex be regarded as a SFH for zoning Any help would be much appreciated!

Christian