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Accessory Structures Zoning Code Amendments – An Overview and Assessment


The City of Portland (Bureau of Planning and Sustainability) regularly reviews and updates planning and zoning codes through a process called RICAP (Regulatory Improvement Code Amendment Project). Part of the current RICAP process focuses on “Accessory Structures”. The first part of this post is intended to summarize some information about these updates. At the tail end, I’ll give a little editorial assessment of them.

The proposed code changes are for “accessory structures” at large, and therefor apply to detached ADUs, detached bedrooms, garages, studios, and other accessory structures. For a thorough review of all of the proposed changes, you can read through the documents posted at  The proposed updates are partially based on developing standards that address some of the chronic adjustments/variances that have been sought for ADUs in recent years.

Because we at distill and assess ADU information for your reading pleasure, I’m providing a brief synopsis of the changes as they pertain to detached ADUs. Additionally, I’m linking here to a distilled 6-page version of the changes that I’ve developed as a handout for my ADU classes. If you’re a homeowner, you can share this handout with your designer. Or, if you’re a designer/builder, you can use this handout to convey the proposed changes to a prospective homeowner client.

The proposed Accessory Structure code updates go through a public comment comment period and then eventually go through a vote before City Council before being adopted into code. This vote is likely to take place in late fall/early winter of 2015/2016. So, it’s possible that there will be changes to the proposed language and it’s also possible that these measures will not be adopted at all.

Proposed ADU changes_6_22_15_Kols_summary

Proposed Accessory Structure Regulation Updates
•Currently, only garages that meet certain size and location requirements are allowed in the side and rear setbacks. The proposals modify these standards to allow any small (< 24′ of length within the 5′ setback), single story (maximum 15 ft. high) detached covered structure in the side and rear setback, including ADUs.
•Currently, all ADUs must meet compatibility standards relative to the primary house, while other detached accessory structures do not. The proposal requires only ADUs over 15 ft. to meet design compatibility standards relative to the primary house, or a revised, alternative set of design compatibility standards.
• Currently, all detached ADUs must meet compatibility standards relative to the primary house. The proposal removes all design compatibility standards for ADUs that are less than 15′.
•Currently, the height of ADUs is limited to 18ft. The proposal increases this height to 20ft for ADUs. Meanwhile, other accessory structures, such as garages, had height limits of 30ft, and they’re being reduced to 20ft.
• Currently, the regulation requires the ADU to be either at least 60 ft. from the front lot line or 6 ft. behind the house. The change amends this standard to 40 ft. from the lot line or directly behind the rear of the house.

That is the quick synopsis of the changes, but if these changes have any impact on your situation, read through the 6-page version of the changes to get a better understanding of the changes.

Beware that these proposed changes are not a foregone conclusion. Therefor, planning/zoning staff at BDS (Portland Bureau of Development Services) will not be able to give you information about these proposed changes, or to speculate about whether they’re likely to pass.

My editorial assessment of the proposed changes

While planning/zoning staff at BDS can’t speculate, I can. My take is that based on the generally positive feedback that the changes have received during the public comment period, they are likely to pass into code. Of course, it’s hard to predict what political factors may arise before City Council votes on them, but I think it’s a fair bet to think that these changes will pass.

Therefor, if the changes have a potential to result in a significantly better project for you on your property, I would consider waiting till these changes pass. Of course, with the SDC waiver set to elapse on July 31st, 2016, by waiting till December of 2015, you will be putting yourself into a tight time window during which you can submit your designs to BDS and take advantage of the SDC waiver. And no, we don’t know know whether the ADU SDC Waiver will be extended, so to be safe, proceed with your ADU planning as though the SDC waiver will not be extended.

I was in a focus group that helped to scope out the changes, so I may be biased here. But, I think these proposed code changes are great for ADUs.

They’re not revolutionary updates to the ADU code; they’re incremental changes. For example, they don’t go so far as to allow for 2 ADUs on a property (internal and external), they don’t allow an ADU on a property with a duplex, they don’t allow for tiny houses on wheels to considered an ADU or a habitable accessory structure. And it would be nice to see some of these more significant changes adopted. But, as far as incremental changes go, these are very good ones.

1) The biggest change (deliberate or not) is the new incentivization towards smaller ADUs. Using these changes, you can A) build within the 5ft setback, effectively preserving more of your backyard for the use of both the main house and the ADU occupants and B) you no longer have to visually match the main house.

This code change creates a double incentive towards smaller ADUs, which necessarily have the likelihood to be more universally accessible (eg. no steps), and which, by virtue of their small size, necessarily have a lower energy and material resource footprint.

2) Whereas “prefab” designs are not possible with ADUs currently due to the design matching requirements, this set of changes opens up that possibility for ADUs that are 15′ or less in height.

What I don’t like about the prefab ADU concept is that the design is not necessarily contextualized architecture (ie. it could be off-the-shelf designs from students in China who have never seen your property). There will inevitably be a large consumer demand for the cheapest “ADU model” under these code changes.

What I do like is that there is the possibility for someone to develop a more affordable, scalable design, which could theoretically lower the barrier to ADU entry for many homeowners who can’t afford a custom ADU design/build on their property. Given that these designs would likely be a) very non consumptive and b) likely universally accessible, I’m ok with sacrificing my aesthetic preference for contextualized, customized designed in favor of the broader social benefits that are incentivized here via these code amendments.

3) The design matching requirements for 2 story ADUs is being liberalized significantly. While my bulleted synopsis above doesn’t cover this, the 6 page handout does (on page 6.) While there are still some limits on  >15′ ADUs, the codes will be liberalized for the roof pitch, exterior finish materials, window, trim, and eaves. This flexibility will allow for architects to be more more creative with the exterior look and feels of all ADUs.

4) Going from an 18′ to 20′ height limitation for ADUs that are not within the 5ft side or rear setback, will prove incredibly useful for homeowners who are going up two stories. The 18′ height limit has always proven to be just a hair shy of what makes for a comfortable staircase layout. Adding 2 ft to the height limit doesn’t seem like a big deal, but it should result in more easily designed floorplans for ADUs.

Overall, we’re happy with the proposed accessory structure code changes. It’s great to that the City of Portland has invested so much attention to refining portions of the code that have proven problematic for accessory structure permit applicants.

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

12 comments on “Accessory Structures Zoning Code Amendments – An Overview and Assessment

  1. Eli Spevak
    July 27, 2015

    Nice post!

    Although this is probably only of interest to process wonks, I’m pretty sure this code update isn’t technically part of RICAP. I think the RICAP process contained a whole slew of code changes, and the ‘accessory structures’ batch of changes for which we sat on the focus group was deliberately excerpted out of RICAP so it could get more attention and have the latitude to make genuine legislative/policy changes (whereas RICAP is geared towards simple clerical stuff that’s unlikely to create any political buzz).

    You could check with Phil. And really – it might not be worth tweaking the post to correct. Or maybe if it is, Phil could suggest alt. opening language.

    – Eli


    • kolpeterson
      July 28, 2015

      Gotcha. I’ve updated the post verbiage accordingly.

  2. Eli Spevak
    July 28, 2015

    7/28/15 Update: Portland has finished taking comments on the Discussion Draft and will be publishing a Proposed Draft later in August. The review date by the Planning & Sustainability Commission is tentatively scheduled for Sept. 22nd. Those interested can check the Bureau of Planning and Sustainability website for updates.

  3. Handy
    September 1, 2015

    Require all detached covered accessory structures over 15 feet in height to meet revised compatibility standards. The project focuses on detached accessory structures in residential zones, but code amendments are proposed within all the base zones as well as the accessory dwelling unit chapter in the Zoning Code.

  4. Ray Culi
    November 16, 2015

    I viewed the Nov 12th City Council hearing and thank Kol, Eli, and others for their testimonies in support of the proposed changes for Accessory Structures. As a designer of ADUs in Portland and currently incorporating some of the proposed amendments into current projects, what can you tell us about the next steps in the code amendment process? When is the City scheduled to make a decision?

    • Steve Jepson
      October 4, 2016

      Could your recomend an Engineer in Portland ?

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  8. atype1mom
    January 22, 2016

    Any experience with a residential property currently zoned CN1? It looks like the biggest downfall is paying commenter vial fees for the project, however the setbacks and height are much more lenient. Any comments?

    • Kol Peterson
      January 22, 2016

      Not sure what you mean by ‘commenter vial fees’.

      But yes, this code expands the possibility of building ADUs in new zones, if there’s a only s single family residence on the property.

  9. jennifer slater
    September 12, 2017

    Question if you have a basement you wamt to make legal w 800 sq ft of space as a accessory st and also another detached acc st already built is that allowed?

Comments are closed.


This entry was posted on July 27, 2015 by in Design & Build, News, Policy & Trends.
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