Converting a grandfathered duplex to SFH + ADU

Converting a grandfathered duplex to SFH + ADU

Investor · Seattle, WA · Member since 2015 · 6 posts · 2 votes

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!

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Realtor · Bellevue, WA · Member since 2019 · 882 posts · 1k+ votes
3y

@Sara Ball, I did that and I can show you the steps!

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  • Real Estate Agent · Seattle, WA · Member since 2019 · 243 posts · 246 votes
    3y

    Nice! This is an awesome opportunity for you. I'd recommend reaching out and speaking to a real estate attorney about how to best approach this. 

    I haven't gone through the conversion you're trying to do, but I'm currently working on building out a DADU on an NR3 lot myself, so happy to knowledge share what I learn along the way. Feel free to DM me to chat more!

  • Realtor · Bellevue, WA · Member since 2019 · 882 posts · 1k+ votes
    3y

    @Sara Ball, I did that and I can show you the steps!

  • Investor · Seattle, WA · Member since 2015 · 6 posts · 2 votes
    3y

    @Sherief Elbassuoni Thank you! I see your number in your signature - I will give you a call this morning.

  • Member since 2020 · 2 posts · 0 votes
    2y

    @Sara Ball and @Sherief Elbassuoni, I am in a similar situation where I need to convert duplex SFH + ADU to be able to build a DADU.

    Sherief, if I may, I would love to connect with you and learn from your experience. Sara Ball, did you end up going through the process?

    Best,

    Parth

  • Jay HurstBusiness Member
    Lender · Dallas, TX · Member since 2017 · 1k+ posts · 1k+ votes
    2y
    Quote from @Parth Panchal:

    @Sara Ball and @Sherief Elbassuoni, I am in a similar situation where I need to convert duplex SFH + ADU to be able to build a DADU.

    Sherief, if I may, I would love to connect with you and learn from your experience. Sara Ball, did you end up going through the process?

    Best,

    Parth

     @Parth Panchal One thing you would want to consider is that Fannie/Freddie will NOT finance a 2-4 unit building with an ADU. So, that can potentially limit your buyers when/if you go to sell. There are non-conventional programs that will allow on an exception basis but not ever one can qualify or will even know about those programs.

    See here for Fannie:  https://selling-guide.fanniemae.com/Selling-Guide/Originatio...
     

    Hurst Real Estate, INC4.987 Reviews
  • Investor · Seattle, WA · Member since 2015 · 6 posts · 2 votes
    2y

    @Parth Panchal I did and it was relatively painless. In construction phase now. Happy to discuss - feel free to call or DM me!

  • Member since 2020 · 2 posts · 0 votes
    2y

    Thank you Sara!, DM sent

  • Investor · Clairemont, CA · Member since 2011 · 3k+ posts · 2k+ votes
    2y

    @Jay Hurst I thought Freddie had actually chamged their guidelines to finance MFR with a single ADU...

    https://guide.freddiemac.com/app/guide/section/5601.2

  • Jay HurstBusiness Member
    Lender · Dallas, TX · Member since 2017 · 1k+ posts · 1k+ votes
    2y
    Quote from @Matt Devincenzo:

    @Jay Hurst I thought Freddie had actually chamged their guidelines to finance MFR with a single ADU...

    https://guide.freddiemac.com/app/guide/section/5601.2


     That is great!  I had not noticed that change. 

    Hurst Real Estate, INC4.987 Reviews
  • Member since 2024 · 1 post · 0 votes
    2y

    @Sara Ball I am also looking to convert my duplex into an SFH+ADU and wondering if you'd be willing to talk with me for a few minutes about the process you went through successfully. I'm new to Bigger Pockets and still figuring things out around here ;)

  • Investor · Seattle, WA · Member since 2015 · 6 posts · 2 votes
    2y

    Sure, happy to chat. I just gave you a call from your DM so you have my number. Feel free to reach out there.

  • Member since 2025 · 2 posts · 0 votes
    10mo

    Hi @Sara Ball, we are considering converting our Seattle duplex into a single family home with an AADU and I would really appreciate hearing about your experience if you have a few moments to chat! (I am also new to this platform but seems like there is a way to connect?) 
    Best, Amelie 

  • Member since 2025 · 2 posts · 0 votes
    10mo

    @Sara Ball

     Hello! I think I failed to properly address you in my former post (rookie mistake!), so I am giving it another try here! This is what I wrote:

    We are considering converting our Seattle duplex into a single family home with an AADU and I would really appreciate hearing about your experience if you have a few moments to chat! (I am also new to this platform but seems like there is a way to connect?)
    Best, Amelie

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