Building an ADU in San Jose

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Jason Hsiao
Investor · Pasadena, CA · Member since 2015 · 269 posts · 189 votes
7y

The assessed value of your ADU should be close to the cost of building it, or replacement cost. Your basis for land and improvement should stay the same. "Fair market value" is just a fancy way of saying what another person is willing to pay for it. With the high construction costs nowadays it's hard to add that much value, plus ADU's don't sell at the same $/sqft as the regular house, and there's not a steady readily available comparable properties to base valuation so the easiest method is replacement cost.

I hosted a Meetup and wrote about ADU's on my website. I have a few architect friends that have gone through the process in multiple cities. It is definitely a hot (and evolving) topic so thanks to @Wayne Brady for creating a thread. If you have other questions or need referrals shoot me note!

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  • Brian Ng
    Member since 2019 · 1 post · 0 votes
    6y

    Hey All - This is all great info! For drawings, what's the ballpark I should expect to spend for changing my garage into an ADU?

    0Reply
  • Laura Blair
    Developer · Oakland, CA · Member since 2015 · 13 posts · 15 votes
    6y

    For drawings-$2000-$3000 for drawings, not including structural from an engineer.  

    0Reply
  • Spencer Hsu
    Realtor · Palo Alto, CA · Member since 2016 · 76 posts · 20 votes
    6y

    That's pretty affordable for drawings so I would love your contact @Laura Blair. I've seen costs of about $7k+ for garage conversions from architects.

    0Reply
  • Laura Blair
    Developer · Oakland, CA · Member since 2015 · 13 posts · 15 votes
    6y

    Designers are cheaper than architects.  I will message you

    1Reply
  • Namit Raisurana
    Investor · San Carlos, CA · Member since 2017 · 37 posts · 17 votes
    6y

    Lot of good information on this thread. I am on a similar journey trying to build an ADu on my property in EPA. Considering the construction cost would be mimimum at 250/sf, + all fees, + all finishing and appliances, a 600sf adu might end up costing 200k+. I am able to find prefab options around the same price which will be completed much faster and with much less headache. Did any of you look into that? I started a thread specifically for that

    1Reply
  • Account Closed
    Santa Clara, CA · Member since 2018 · 100 posts · 71 votes
    6y

    Hi All, My ADU construction has started. I am doing it as an owner builder. Its taken me a while to get to this stage but I will be happy to share my experience and answer questions.

    3Reply
  • Medi Sarwary
    Pleasanton, CA · Member since 2016 · 73 posts · 48 votes
    6y

    @Account Closed Looks like its coming along nicely, quite large as well

    0Reply
  • Account Closed
    Santa Clara, CA · Member since 2018 · 100 posts · 71 votes
    6y

    @Medi Sarwary Thank you, about 720 sq feet and we are applying a revision to add another 120 sq feet. 

    1Reply
  • Spencer Hsu
    Realtor · Palo Alto, CA · Member since 2016 · 76 posts · 20 votes
    6y

    Hey Pooja, as an owner, how much are you saving? Are you still hiring GCs then or just subs?

    0Reply
  • Account Closed
    Santa Clara, CA · Member since 2018 · 100 posts · 71 votes
    6y

    @Spencer Hsu I had a very specific design for the ADU. I was able to hire an amazing architect who worked with me on all the changes and helped me get the permit. I'm sure I drove her crazy sometimes with the tiniest of the details. I feel working with a GC would have been quite costly due to the changes I made along the way and I feel I might have compromised on the design. So yes I do believe I did save - how much I am not 100% sure. I hired a foundation contractor, framer and now my best friend who is a flipper has a team & is helping me finish up the rest.

    0Reply
  • Spencer Hsu
    Realtor · Palo Alto, CA · Member since 2016 · 76 posts · 20 votes
    6y

    Awesome, can you share those contacts? Are you happy with them all? You can PM me :)

    0Reply
  • Account Closed
    Santa Clara, CA · Member since 2018 · 100 posts · 71 votes
    6y

    @Spencer Hsu yes absolutely ! I am happy with all so far

    0Reply
  • Christian NielsenPro Member
    Architect · Santa Cruz, CA. · Member since 2020 · 12 posts · 22 votes
    6y

    @Account Closed Congratulations on your ADU build! Looking forward to seeing more photos along the way.

    1Reply
  • Namit Raisurana
    Investor · San Carlos, CA · Member since 2017 · 37 posts · 17 votes
    6y

    Hey @Account Closed- what is the approx price per sqft construction cost you ended with? 

    0Reply
  • Account Closed
    Santa Clara, CA · Member since 2018 · 100 posts · 71 votes
    6y

    @Namit Raisurana I am estimating about $275 sq feet for build cost (including all utility connections & separate electric meter). Soft Cost is extra. I feel this is fairly accurate and I am not likely to have any surprises (keeping my fingers crossed!). We have already done all the plumbing connections and I have talked to PG&E already on getting another meter, I also already have another address for the ADU.

    The design of this house has 2 dormers & 100 sq feet loft space which is not included in the 720 sq feet. To be able to get more headroom in the loft, we had to go with a higher pitch roof. All this added about 10K orelse it might have been approx $260 sq feet. 

    1Reply
  • Account Closed
    Santa Clara, CA · Member since 2018 · 100 posts · 71 votes
    6y

    @Christian Nielsen Yes absolutely! I will add more pics soon

    0Reply
  • Latief Bazaz
    Member since 2021 · 1 post · 0 votes
    5y

    Hi Pooja,

    Came across your ADU related posts. Your project must be complete by now. Can you please share some pics of your ADU

    Thank you

    0Reply
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