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To DADU or Not To DADU–Seattle’s ADU Debates

There’s some lively discussion in Seattle these days about relaxing restrictions for Detached Accessory Dwelling Units (DADUs). There doesn’t appear to be strong opposition to DADUs, but some are expressing fears about what may happen if the regulations are relaxed.

In my opinion, these fears haven’t proven to be warranted, and should not drive decisions that could hold back progress.

As is typical with public discourse about ADU regulations, well-intentioned people are expressing how relaxing rigid owner occupancy requirements, and eliminating off-street parking requirements on these accessory units is going to a) change the character of their single family neighborhoods and b) exacerbate the City’s parking problems.

“…the net effect of these proposed DADU/ADU changes likely would be to drive up land values, taxes and rents throughout single-family-zoned areas, not just on sites that include a DADU or ADU. This only creates greater hardship for owners and renters alike.”  – see more commentary here

Sentiments like these can be found in these two recent pieces that speculate on how relaxing DADU regulations will hurt Seattle.

Speculative rhetoric is par for the course whenever cities are considering loosening up on ADU owner occupancy and off-street parking regulations. These concerns are typically raised by neighborhood groups or by some number of the city’s elected officials. Indeed, some variation of this same rhetoric occurs in seemingly every US city that has longingly considered its options for making ADUs easier to permit.

I follow these local ADU policy and regulation debates nationally, and observe the same fears coming up time and time again. Here’s a NY Times article from 1995 with the same tired, speculative rhetoric. Detached ADUs, in particular, seem to trigger speculative but adamant positions. Indeed, if history is any indicator , when Seattle offers an opportunity for public comment, it will likely be full of voices that will negatively speculate about how relaxing DADU regulations will be bad for Seattle’s single family neighborhoods.

In Seattle’s case, there are already roughly 1,200 attached ADUs. In Portland, like in Seattle, there are also roughly 1,200 ADUs. Unlike in Seattle, there is no large distinction drawn between attached and detached ADUs, and most of Portland’s ADUs are detached (approximately 2/3rds). This lack of architectural form distinction between detached and attached ADUs in Portland is most noticeably apparent from the names such units are granted: Porltand refers to them all as “ADUs”, instead of having distinct names as there are in Seattle, WA (ADUs and DADUs) and Vancouver, BC (accessory apartments and Laneway Houses).

Another distinction that differentiates ADU regulations in Portland and Vancouver from ADU regulations in Seattle is that the former two cities have:

a) no owner occupancy requirement

b) no additional off-street parking requirements

Also, it’s apparent that both Portland (800) and Vancouver (1000+) have much more detached ADU development happening than Seattle does (200).

Fortunately, due to this relatively abundant detached ADU development, we have real data from a 2013 survey of Oregon ADU owners, with analysis from which to draw statistically valid conclusions about these two common fears.

a) Does removing owner occupancy requirement cause negative impacts on the neighborhoods?



Answer: No

b) Do ADUs cause neighborhood parking problems?


Answer: No

Though parking and owner occupancy requirements may be illogical or ill-founded regulations, these two regulatory zoning barriers, along with mandatory discretionary reviews, amazingly, help prevent ADUs from being built in cities across the country. I colloquially refer to these three regulatory barriers as the “Three Poison Pills that Kill ADUs”.

If a city like Seattle has come to the conclusion that it wants to have more DADUs, I believe that these owner occupancy and parking requirements should be relaxed first and foremost. Every other regulatory rule change under consideration is somewhat irrelevant to DADUs if these two restrictions remain in place, as these two regulations alone tend to prevent development.

What will happen if owner occupancy regulations are removed and off street parking requirements are removed. Here’s what will happen:

If those two poison pill regulations are relaxed….

and if other preconditional uses are not added as requirements….

and if the real estate market timing is just right….

and if financing options are made possible by forward thinking local banking instutitions….

and if a guantlet of other nuanced zoning regulations aren’t written to be too restrictive,

…..then maybe, just maybe, Seattle will start to see an uptick in DADU development. And most people (except ADU policy wonks like those reading this post) will never even notice the uptick.

In Portland, the numbers of ADUs built each year has almost doubled each year after loosening its regulations and waiving its system development fees in 2010. And we still only had 360 ADUs permitted in 2015. In a city with over 250,000 housing units, we had fewer ADUs built in 2015 in the entire city than were added by a single, large apartment complex.

Detached ADUs are a rare and delicate grassroots housing development form that must walk a tightrope of economic and regulatory obstacles in order to survive.

Layer the formidable capital cost (and the lack of matured financing tools), with the fact that ADUs are not typically a very profitable form of speculative development for professional developers, and it quickly becomes apparent that only a small fraction of highly economically and socially motivated homeowners/developers will have both the will, and the financially capacity to add these small, but expensive, structures to their property.

Seattle is not going to be overrun with ADUs anytime soon. Even with major regulatory easements for ADUs, it would be extremely unlikely to see a signficant number of detached ADUs built (eg. 1,000 city wide) in the first several years after loosening restrictions, due to the formidable cost of ADU construction for homeowners. This is a specialized form of housing that seems to takes years to foster.

If these regulatory barriers are relaxed, and more DADUs are actually built as a result, and the sky does start to fall as some speculate, the city can simply adjust the regulations as needed.

Conversely, if Seattle doesn’t remove those two regulations, DADUs will probably be stuck in same rut that they are stuck in now. In 3 years, or 5 years, or 10 years, DADUs will continue to be developed at a lonely, flat, and relatively insubstantial rate of roughly 50 new DADUs year. And in 3 years, or 5 years, or 10 years, if the City again decides that it feels compelled to induce more DADU development to meet policy objectives, the City will once again, have to go through another public process. From my vantage as a connesuier of ADU regulatory best practices, this …/political-ADU-debate/rejection-based-on-NIMBY-fears/no-ADUs-are-built/political-ADU-redebate/… policy cycle is a observable and predictable fact of life in the current chapter of ADU regulation politics in cities across America.

No good data exists to back up the claims that are made against the parking impacts or the owner occupancy problems that occur when those regulations are relaxed. In fact, there are only two North American cities with substantial, permitted detached ADU development: Portland, OR, and Vancouver, BC. I’m familiar with the limited survey and research data that exists about ADUs in these cities. And, in both cases, the speculative issues that seem to cause such great worry, are not causing actual problems in real life. Here’s a summary post of fact based evidence about the impacts of permitted ADUs in Oregon.

ADUs aren’t a new concept for Seattle-there’s already 1,200 attached ADUs. In fact, it would be possible to suss out what the social impacts of these 1,200 accessory units have been thus far regarding these two fears. Look at neighbor complaints of instances when an ADU occupant didn’t choose to park in their off-street spot. And then look for examples of neighbor complaints about the instances when the owner opted to break the rules by not living on the property even if they were supposed to do so. Though these two circumstances surely exist, I’m guessing that there haven’t been such complaints.

These parking and neighborhood degradation issues don’t actually seem to crop up as real problems in real life in Portland or in Vancouver. Instead of basing policy on dystopian outcomes, I would recommend that Seattle’s City officials instead consider easing up on all potentially restrictive regulations on DADUs for a few years. At that point, they can check to see whether any of the fears that were raised came to fruition.

Maybe in a few years, if Seattle is lucky, there might actually be a more substantial number of permitted DADUs from which to draw some fact-based policy conclusions. Meanwhile, I recommend that Seattilites take a deep breath, and just say, “To DADU”.

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 “To DADU or Not To DADU–Seattle’s ADU Debates

  1. Laurie Lohrer
    February 4, 2016

    You’d feel different if it were your backyard……. I was appalled when owners of the house next door ( who BTW never once spent a night in the house next door, renting it out immediately after buying it), built a huge 2-story DADU about 4 feet from our common fence. The house is west of ours, so of course it casts a big shadow over (what used to be) our raised bed, organic vegetable garden. Our back deck once was a quiet private place, not they look down on us, so there;s no privacy in the back yard or the deck, we don’t use them anymore.

    Did we know anything about it before the contractors license and project notices went up? HECK NO.They never talked to us at all, let alone advising of construction disruption, limiting our access to sun. It’s totally out of proportion to the neighborhood homes. So much for doing the right thing and respecting your neighbors.

    Councilperson O’Brien may think he’d love to have someone living in his backyard, but I really doubt it if it came to pass.

    There’s a reason why some of us decided to invest in homes instead of apartment living. Good God, we need a little separation living in the city, there’s enough density already to drive us all nuts. “Too many rats in the cage”, according to my husband. Just saying…….

    Laurie Lohrer

    • Jay
      November 8, 2017

      Thank you Laurie for your comment. The reason there are not more ADUs in Seattle is not because of regulations restricting them it is because we don’t want them in Seattle. This blog is written by a proponent of ADU/DADU construction trying to drum up business.

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This entry was posted on January 19, 2016 by in Opinion, Uncategorized and tagged , , .
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