[UPDATE October 9, 2025: Reno Adopts ADU Ordinance: What Homeowners & Investors Should Know]
If you haven’t heard yet, you will soon: Amazon invested millions into prefab homebuilder Plant Prefab via the Alexa Fund. Headlines at the time included:
- CNBC: Amazon makes first investment in a homebuilder, backing start-up focused on prefabricated houses
- Curbed: Amazon invests in prefab startup focused on smart home tech
- Inman News: Amazon just invested millions into a prefab homebuilder startup
- Fast Company: Alexa-powered Amazon houses may be closer than you think
While most stories focused on Alexa and smart-home tech, I was more interested in the prefab homes themselves. Plant Prefab offers a range of models and custom options. One that caught my eye was the AD1 Accessory Dwelling Unit (ADU)—a ~400 sq. ft., one-bed/one-bath unit with a base price under $100,000. It can work as a stand-alone “tiny house,” a guest casita, or a granny flat.
Why ADUs Are Interesting
ADUs can unlock flexible living arrangements and potential income: a guest house, office/studio, long-term rental, or multigenerational living. Naturally, my first question was: “Am I allowed to install one of these on my property?”
What Washoe County Calls a Detached ADU
Washoe County, Nevada, defines a Detached Accessory Dwelling (DAD) as a self-contained dwelling on the same lot as the main home, physically separated from it. Whether you can build one depends on lot size, zoning, and a few other factors.
Quick Eligibility Snapshot
| Question | County Guidance (Summary) |
|---|---|
| Can I build a DAD? | It depends on lot size, zoning, and utilities (see details below). |
| Lot size |
|
| Zoning |
Tip: Look up your property’s zoning on the Washoe County Assessor site. |
| Maximum size |
|
Important: Rules and processes can change. Always verify the latest requirements with Washoe County Planning & Building and the Health District before you design or purchase a unit.
My Take
Unfortunately, my own lot isn’t large enough to allow a detached unit. 😞 But many Washoe County homeowners do qualify. If you’re on a larger lot—or in GR/GRA zoning—an ADU could be a practical path to flexible living space or long-term rental income.
What’s Next?
- Confirm your zoning and lot size.
- Talk with a designer/architect about setbacks, utilities, and access.
- Check permit path (Special Use Permit, DADAR, or straight building permit).
- Run a quick cost vs. rent analysis if you’re considering long-term leasing.
Note: ADU rules vary widely by city and county. Your mileage may vary.
Curious if your Washoe County property qualifies? I’m happy to check your zoning and talk through options.
Guy Johnson, REALTOR®
Keller Williams Group One, Inc.
📞 (775) 722-4011 | 📧 guyjohnson@kw.com
12 Responses
This is great information Guy, thank you. I had this in the back of my mind, having just over an acre with lots of unused space. The second septic/size requirement is a real letdown though! I wonder if some of small rentals I see out in Washoe Valley on other larger properties are in compliance.
Thank you, Vale. The second septic/size requirement is what eliminated me, as well.
I wonder if there are any kind of exceptions for the number of residents in the primary residence?
Vale, give the Planning Division ( 775.328.6100) a call and let us know what you find out.
I don’t think there are really any exceptions here. 1 acre and an accessory dwelling – needs 2 septic systems. Doesn’t matter how many people are living in unit. I think the extra septic system is just a trap to catch people – kind of like a fishnet – And it obviously works.
We added an in-law unit for my mil when we purchased our home. We were able to avoid the 2nd septic by attaching it to our home, hence eliminating the free standing element. I believe the current septic tank size was also a consideration. The unit is private with a separate exterior entrance. Fortunately our home was conducive to adding it with a garage underneath as well.
Hello Ellen,
Thank you for sharing your first-hand experience with the readers. Much appreciated.
– Guy
Thank you Ellen for providing your insight on attaching a 2nd dwelling to the main house. I think that may be the route I take as well.
I recently bought 10 acres in north red rock area can I instal a prefab accessory dwelling to live in? Without having a primary residence. I’m totally off grid
Hello Morgan. Thank you for your question. I would recommend starting with the Washoe County Planning and Building Division to get up-to-date answers.
Hi , I am wondering if I could add a prefab dwelling to my property in Sparks. We do not have C C R ‘s . My daughter is struggling to pay rent and all the bills with her two small children. Our home is 1616 square feet, with regular city sewer. We already have a big concrete pad on the side of our house ?
Thank you for your question, Marilyn. I would suggest contacting the Washoe County Planning and Building Division.