Converting a grandfathered duplex to SFH + ADU

[Sara Ball]

We have a nice, large lot (7500sf, level, no trees) in a prominent NR3 zoned location in Seattle, currently serving as a grandfathered duplex. With the 2019 ADU law, we are considering converting the duplex to a single family home plus ADU, so that we can build a DADU in the ample backyard. Does anybody know about the process to convert a grandfathered duplex to an SFH + ADU? We would love to hear from anyone who has been through is process! Are there any foreseeable downsides to this conversion? What kinds of code updates should we expect this to trigger? It seems like a really cool opportunity, so we'd love to participate. Thank you so much, BP community!