Accessory Dwellings

A one-stop source about accessory dwelling units, multigenerational homes, laneway houses, ADUs, granny flats, in-law units…

The Ascent of ADUs in Portland 

Portland is leading the charge in ADU development nationally. Data provided by the City of Portland shows the impresssive growth rate of ADU permits issued from 2010-2016.


In 2016, 616 permits were issued, 20 times the average number of permits issued each year before Portland’s SDC waiver in 2010. Without a doubt, the SDC waiver has played an invaluable role in increasing public interest in ADU development following the Great Recession of 2008.

The total number of ADU permits issued in Portland is roughly 2,200. Of those, roughly 1,500 ADUs have actually been completed. Based on historic averages, 85% of those 2,200 permit holders will have completed their ADUs by the end of year. So, by January 1st, 2018, Portland will have roughly 1,900 ADUs on the ground.

The ADU market is hot, but overall, there’s still a very small number of ADUs relative to single family homes, duplexes, multifamily apartments, and most other housing types in Portland. Portland has approximately 148,000 single family residential houses. So, ADUs can be currently found on ~1% of single family residential properties.

There’s incredible opportunity and untapped potential for more small housing in back yards and basements in Portland.

ADUs are fairly new to the housing scene, and development pathways are getting established, and new ones are being explored.

While some designers and builders are working on 10+ ADUs a year, many are just now starting to get their feet very wet with ADUs. Realtors are getting trained in how to assist homeowners in buying and selling properties with “ADU potential”. Lenders are starting to come around to the prospect that there is a market need to be filled, and figuring out how to best assist homeowners who require daunting amounts of liquid capital to actually pull off building these ‘little houses’ on their property. Meanwhile, novel development models and initiatives and specialized small businesses are emerging to support ADU growth. It’s exciting to witness.

This fall, we’ll be running another city-wide ADU tour on September 9th and 10th, 2017. This will be the last ADU tour before the SDC waiver is set to expire for ADUs in July, 2018, so we’re gearing up to make this the biggest ADU tour we’ve ever run.  I’ll post more about the tour in the coming months on

I’m in the home stretch of writing and publishing a book about ADUs, which I believe will be the first and most significant work of its kind. The book is written explicitly to assist homeowners in developing an ADU on their property, to help advocates and politicians unshackle their cities from onerous ADU regulations, which can allow permitted ADU development to flourish much as it has begun to do in Portland, and to help small businesses develop a start-up ADU cottage industry in their city.

Among other things, this book interprets and analyzes the success of steep adoption curve of ADUs in Portland, and attempts to explain exactly why we aren’t seeing this same phenomena in other US cities. It’s not just the SDC waiver that has helped ADUs to emerge in Portland, but the SDC waiver has proven to be pivotal.

And it will also explain why, in the city that is leading ADU development nationally, ADUs are nonetheless present on only 1% of eligible residential properties.

In the months leading up the book launch, I’ll be sharing some of the book’s key findings on

Meanwhile, sign up to receive a free 12-page PDF of pithy reference material, as well as other useful resources about building an ADU and get notified when the book, Backdoor Revolution: The Definitive Guide to ADU Development, is available.

ADU Resource Packet - Google Chrome_2017-06-08_13-57-31

(3/1/2017 correction: The initial post indicated that 663 permits were issued in 2016. It’s actually 615 permits. The initial post said 2,400 total permits had been issued. In fact, the total permits issued between 2000-2016 were 2,216. The post and chart has been updated accordingly). 

About Kol Peterson

Kol is an ADU consultant, advocate and author of Backdoor Revolution: The Definitive Guide to ADU Development. Read more here: and learn about building your own at Email at

19 comments on “The Ascent of ADUs in Portland 

  1. Jane lanusse
    February 27, 2017

    Portland is still not as accepting of ADU builds as it appears! My husband and I are out almost 5k$ after hiring a reputable developer and applied to the city for a variance based on the current structure placement and the property lines. The final denial was actually based on “maintaining the integrity of the neighborhood”. We were planning to build above an existing 2 car garage in a neighborhood of 1&1.5 story homes. We are devastated at the outcome, and until someone tears down or builds up a house in this (one of the final affordable neighborhood left in PDX) we are on hold. The Portland assessor had no problem cashing our check.

  2. Pingback: Not in YOUR Backyard: Cottages, In-law Apartments, and the Predatory Delay of HALA’s ADU Rules | Sightline Institute

  3. Pingback: Is America Ready for a Nation of Tiny Houses? – Hawkins Bay Dispatch

  4. Pingback: Couve Life | Vancouver City Council updates accessory dwelling units rules | Couve Life

  5. Celia Anderson
    January 16, 2018

    Where did you get the numbers for permits issued for ADUs in Portland?

    • Kol Peterson
      January 16, 2018

      From the City of Portland.

  6. Sara Sultan
    March 16, 2018

    What percentage of ADUs built are used for affordable, long-term housing as opposed to top-end rentals and AirBnB accommodations?

  7. Pingback: Two Cascadian Cities Extend Greater Welcome to ADUs | Sightline Institute

  8. Pingback: The Forgotten Green Housing Option: Accessory Dwelling Units | Sightline Institute

  9. Martha Koenig
    August 1, 2018

    Thanks for the data gathering, Kol. Is there now data on how many permits were issued in 2017 and how many so far in 2018? Would love to see the increase percentage.

    • Kol Peterson
      August 1, 2018

      No, we don’t have the data for 2017 and 2018 yet

  10. Jackson
    December 9, 2018

    This is a wonderful success story. Do you know when the 2017 data will be available?


    • Kol Peterson
      December 10, 2018

      I’ll try to post the 2017 and 2018 permit data in early 2019.

      • Jackson
        December 10, 2018


  11. Pingback: Cascadia’s Five Most Important ADU Victories of 2018 - Sightline Institute

  12. Pingback: Can Washington Pass the Country’s Most Ambitious Statewide ADU Reform? - Sightline Institute

  13. Pingback: Washington’s Progressive ADU Bill Died This Week - Sightline Institute

  14. Pingback: Upzoning and Affordability, Explained - UCPcouncil

Comments are closed.


This entry was posted on February 27, 2017 by in Policy & Trends, Uncategorized.
%d bloggers like this: