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Portland, Oregon’s ADU Permit Data for 2020

Observations about ADU Permit data trends

As of July, 2021, there have been approximately 3,350 total permits issued for ADUs in Portland. Here’s the latest annual permit trend chart. 

There was explosive growth in ADUs from years 2010-2018, but the number of ADU permits issued has leveled off in Portland over the last two years. The explosive growth period subsided in 2019 and 2020. 

This number of annual ADU permits (250-300) appears to be the new baseline. This should probably be seen as the natural resting state of ADU development. 

However, it is quite possible that with the new Residential Infill Project regulations coming into effect on August 1st, 2021, that we will see another cycle of robust ADU development in 2021 and 2022. 

If this occurs, it would be due to the fact that existing properties with an ADU will be entitled to add another ADU. The pent up interest in utilizing these new provisions will likely spur more ADU activity than normal in the coming year. It is also possible that professional developers may choose to add two ADUs properties when doing redevelopment. More on this shortly. 

HB 2001 Impacts on ADU Development in Greater Metropolitan Portland 

Due to the impact of regulatory changes spurred by Oregon House Bill 2001, many jurisdictions around Portland are starting to see more ADU activity. This bill removed the ability for jurisdictions to require owner occupancy ordinances for ADUs, which was a provision that impacted more than half of the Portland metropolitan area’s 28 jurisdictions. It also removed the ability for jurisdictions to require off street parking for an ADU, which was a provision that impacted more than 3/4s of the Portland metro’s jurisdictions.

Whereas in previous years, far fewer than 10 ADU permits/year were issued in any neighboring jurisdiction, we are seeing those numbers increase in the past year. I don’t have easy access to actual permit data from all of these cities, but based on my personal observations, I believe that neighboring suburban jurisdictions will see steadily increasing ADU growth in the coming years.

ADU Conversions and New Construction ADUs

Anecdotally, I’m seeing more interest in garage and basement conversions than in the past. This may be due to skyrocketing construction costs. Whereas new ADU construction costs are skyrocketing in cost along with all other construction, conversions seem to be coming in at costs akin to previous years. 

New construction 800 sq ft ADUs these days are generally coming in at over $300K. Conversions are coming in at $125K or less as they had in previous years. 

That ADU conversions are staying relatively ‘affordable’ is likely due to fact that ADU conversions do not require as many different subcontractors (eg. foundation, framing, roofing, siding). Many of these tradespeople are extremely busy and backed up. Perhaps this labor shortfall is due to COVID’s surprising impact of homeowners investing more of their money into property improvements, and this is partially what is keeping contractors so busy. Or, perhaps this is just due to general labor shortages in the trades since the housing crash in 2008. 

This analysis is based on personal observations, so these should be understood not as science, but as strong hunches. 

Here’s a new analysis I’ve never been able to do before. In previous years, it’s been evident that the great majority of ADUs were added significantly after the single family home was originally built…often a 100 years after. But lately, more new single family home construction has included ADUs. These ADUs typically are developed in the form of basement ADUs in new spec homes. 

This graphic below depicts the % of ADU construction that was comprised of ADUs being added to a property with an existing single family home compared to the % of ADU construction that was comprised of ADUs being added simultaneously to a new single family home. 

From 2010-2020, 39% of the ADUs that were constructed were done along with new single family homes. 61% were added asynchronously from the construction of the single family home; or said another way, the ADUs were added as incremental infill housing development. 

Impacts of COVID on ADU Development

“Has COVID increased the number of ADUs being built?”

This is one of the more common questions that I’ve received from journalists since March of 2020 when pandemic shutdowns began. Predictably, there was a dramatic drop in ADU permits in March and April, 2020, as the country entered into a lockdown and the City of Portland attempted to transition to an entirely digital permit intake process. Beyond that one dramatic dip in March & April 2020 however, there’s no discernable pattern on ADU permits since the pandemic.

Indeed, it’s unlikely that we will be able to see much statistical impact on ADU permits from COVID. Typically, ADU development takes at least a year, so even if someone definitively decided to build an ADU in March, 2020, they may likely be still building that ADU today. So, their ADU wouldn’t necessarily be reflected in permit data until we have aggregated 2021 permit numbers, which won’t be till sometime in 2022. More commonly, deciding to build an ADU will take a year or two, so people who have been motivated to build an ADU due in part to COVID, will still be the design development phase of the process and will begin in earnest in the next couple of years.

That said, it’s fair to say that in general, the concept of ADUs have become far more culturally popular and accepted since the pandemic began, in part due to the impacts of COVID on people’s values towards housing flexibility. This is due in part to the workforce migration toward teleworking from home, and in part to do more multigenerational housing interest spurred by COVID. 

Residential renovation companies and accessory structure companies have certainly been busy adding additional living space; but whether this directly correlates to an increase in permitted ADUs is difficult to say.

What I see more than actual ADU growth, is a tremendous wave of policy interest in ADUs nationally (and middle housing more broadly). The number of articles that are covering new ADU regulation changes in jurisdictions is astounding. This isn’t to say that all of the new codes are written especially well from an ADU advocacy perspective, but at least many more jurisdictions are taking small steps in a positive direction towards updating their ADU regulations to be less onerous and restrictive.

Frankly though, there’s still a very long way to go in dramatically overhauling ADU regulations to meet what I would classify as minimally acceptable ordinances and development standards—like along the entire East Coast.

But, I suspect that we will continue to see significant swells in ADU development across the country for decades as regulations actually loosen up. If Portland’s ADU permit trends are any indicator, this explosive growth may occur jurisdictionally for a handful of years, and then stabilize. The most explosive growth for ADUs in the country is currently in Los Angeles. In the coming years, I anticipate the Bay Area will be equally explosive. As other states like Connecticut and New York pass decent ADU legislation, perhaps they’ll be the next areas with dramatic ADU growth.  

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

2 comments on “Portland, Oregon’s ADU Permit Data for 2020

  1. dirkknudsen
    July 22, 2021


    Great write-up. These points all track with what I have seen as well. I am just aghast at how slow things are to change here in Hillsboro where jobs are creating a massive need. As a broker I see many people willfully violating the law and putting in garage bedrooms and flats. SRO Bedroom occupancies are the new rage out here. Up to $1200 per bedroom. That is making investors salivate as they buy up available inventory and convert homes that were previoulsy owner-occupied to rentals. Not like getting a home is hard enough- our own restrictive policies have now created a situation where homeownership is no longer an option for most, let alone the American Dream. The march to a world filled with Lords and Serfs continues. You are a beacon of light – so keep on shining my friend!

  2. Hiedi Whitehair
    February 25, 2022

    My husband and I are nearing retirement age. We have a 2000+sqft home and live on only the top level (minus garage use). The bottom portion (approx 390sq ft) would make a perfect little studio as well as private entry and small yard space, with very little construction updates needed. Will you please send us any information you have on the necessary steps needed and legal requirements. My husband believes there is a 600sq ft requirement for the additional unit. Is this true? Please advise as this would really enable us to retire more comfortably… Thank you

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This entry was posted on July 22, 2021 by in News, Policy & Trends and tagged , .
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