The apartments are coming!


Invasion of the DADUs

The Seattle City Council just passed, 8-0, zoning modifications that will make it much easier to build backyard cottages and parent-in-law units in the main house, all through the city. That puts us among the first to get on the train (after Minneapolis and Oregon) to overturn the once-sacred protections of single-family zoning.

Here’s a Slate article on how this movement is sweeping the nation, and how the federal government might soon get involved. (Witholding transit dollars from cities that over-protect single family zoning is one way.)

Seattle had made a gesture by allowing backyard cottages in 2010, called DADUs (detached auxiliary dwelling units) and since 1994 ADUs (attached ones, usually in basements), but the regulations were such that few were actually built. A city study also found that the cost of new construction of these units is so high that only affluent homeowners were likely to build the new units. Now two key restraints are tossed: you don’t have to live on the property to make the conversions (are you listening Airbnb developers?), and you don’t have to provide off-street parking.

Even so, I doubt that many units will be built. There are relatively few homeowners who have the means (or the patience) to undertake such major projects. Given the high land costs in Seattle, I doubt that many developers or homeowners can make such conversions pencil out.

Dubious too are the limitations on new houses, meant to discourage construction of new mansions. By limiting new housing to half the square footage of the building lot, nearly all the new houses going up in Seattle now would be illegal, and I can’t imagine the builders, realtors, and homeowners hoping to make a killing will stand for this.

One loophole is that the accessory unit(s) do not count against the allowed square footage. One can easily foresee a situation where most of the new construction of mini-mansions contains a flexible ADU, just as so many of the new apartment projects have street-level retail easily shifted to quasi-retail uses.

A last concern about this seemingly-dramatic shift in Seattle’s beloved single-family neighborhoods (surely one of the great assets of the city) is that we still miss the key element in a balanced city — incentives to build housing for families. Until we find a way to build and protect more of that housing (more bedrooms and lawns), we will continue to be a city of residents who follow the Meet-Mate-Move trajectory. That means a city with thin civic roots.

The city has debated this topic into submission. Here’s the Seattle Times’ editorial board’s last-ditch and slightly hysterical stand against the ordinance just passed. Surely there could be better, gradually, more holistic approaches, as argued by three architects in this op-ed. But these wise suggestions would involve so many years of debate and wrangling that it makes some sense to jump at the resolution on offer, one which the exhausted council (four of the nine heading for the exits) and the reluctant Mayor Durkan will actually sign. So the deed was done, the Rubicon was crossed.

But I overstate my alarm. I doubt there will be a wave of speculative builders, since land values are too high and the regulatory hurdles too many to touch off a property rush. The joker in the deck, I fear, could be the surge in Airbnbs and VRBOs. By and large, you have a cynical but ideal political outcome. Points scored in political heaven for doing the right thing, and political necks protected by allowing but avoiding a gusher of changed land-uses. No harm, no foul.


David Brewster
David Brewster
David Brewster, a founding member of Post Alley, has a long career in publishing, having founded Seattle Weekly, Sasquatch Books, and His civic ventures have been Town Hall Seattle and FolioSeattle.


  1. Three observations: first, the new ADU ordinance will modestly increase the number of housing units, and the diversity of those units.. Putting aside the inevitable arguments about housing affordability, Seattle is growing and we will need more housing units. So that’s a good thing.

    Second, the number of people living in Seattle’s single-family zones is shrinking, both because of the trend toward smaller families and because of more people “retiring in place.” That trend is unlikely to reverse. Single-family home neighborhoods are thinning out, and it makes good sense to look at how to (slightly) increase density there.

    Third, the impact of the ADU ordinance is wildly overstated by its opponents. According to the Environmental Impact Statement, under the new rule there should be about 4400 new ADUs built over the next ten years — 440 per year. After ten years, there will be 1 additional ADU for every 3 blocks. Even if the actual rate is twice what is in the study, it still won’t be noticeable.

  2. I disagree so fundamentally with David and Kevin that a comment doesn’t have room to cite even the bullet-points. If the ordinance required owner-occupancy of the main dwelling unit, I would be all for it; without that proviso, it’s a formula for low-income housing loss and investment-fund ownership.
    I can’t expect even those moderately interested in this issue to read and absorb what one the most expert and engaged urban-development scholars in the world recently posted to The Planning Report: it’s too detailed and fine-grained for web reading. But I hope some readers will download it for future reference. This war is not over:

  3. As tothe paragraph above reading
    ‘One loophole is that the accessory unit(s) do not count against the allowed square footage. One can easily foresee a situation where most of the new construction of mini-mansions contains a flexible ADU, just as so many of the new apartment projects have street-level retail easily shifted to quasi-retail uses.”

    David, what is a quasi-retail use? I don’t find the term in the index of the Seattle Building Code. Or is it only in the unpublished annex to the code labeled “Loopholes”?

    • I was referring to the requirement that streetfronts of new apartments must be retail, but they are often fudged, serving as part of the residence above, a fancy entry, a spare room. Hard to inspect all these places and easy to look “quasi-retail.”

  4. Per Kevin’s comment above, I’ll bet you anything that Seattle’s single-family neighborhoods like mine (Phinney Ridge) will still fee like Seattle single-family neighborhoods in 10 years.

    I was just in Portland last month. Beautiful city, great neighborhoods. Yet many of those neighborhoods have long lived under the yoke of zoning that allowed duplexes and triplexes. The horror!

    Aside from the McMansion ban being too restrictive, imo this legislation seems like a welcome change, and long overdue.


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