Portland’s Bold Move To Encourage More Close-In ‘Middle’ Housing


Missing middle homes, like ADUs, backyard cottages, mother-in-law suites, duplexes, triplexes, low-rise apartments or townhouses, have long fit into urban neighborhoods, often providing more affordable rental and purchase options than single, detached houses. (Image: Sightline Institute Modest Middle Homes Library)

Portland has busted the single-family lock on its zoning code. Last week the Portland city council voted to legalize new forms of “middle” housing with smaller residential units permitted everywhere in Portland. This bold move potentially increases available housing and public open space without increasing building heights at all. 

Aptly named Residential Infill Project (RIP), the package ends a long period of post-war ballooning of house sizes and off-street parking requirements.  These conditions have kept much of the city looking like a tired suburb. Despite similar development patterns, lots of bus transit and years of trying, Seattle has not been able to overcome similar legal obstacles from “neighborhood character” and objections from single-family homeowners.

Middle housing is very traditional but it’s so scarce in Western cities it’s misunderstood. Such modest housing ranges from low-rise multi-family to triplexes and accessory dwelling units (ADUs), attached and detached. If they are designed with landscapes and streets in mind, all those plexes and ADUs fit easily into traditional single-family lots and accommodate small households.

With its size limits, Portland’s package is a gift to all generations, from homeowners needing additional income to starter families looking for housing choices in the city. The new zoning in Portland will allow up to six small units on one typical 50-by-100-foot lot, as long as three of the new units are held to a standard of affordability and one or two are wheelchair accessible.

Just like Seattle, booming Portland needs denser housing along with transit. Towers are expensive, and theydon’t appeal to everyone. Many prefer stepping into their homes from the street, and they like diverse urban neighborhoods with lots of small, safe open spaces. That’s exactly what Portland’s new zoning will encourage, with lower limits on unit sizes and no on-site parking requirements. 

Much lower size limits. As of last week, the maximum size for a new single-family dwelling in Portland is 2,500 square feet, down from a previous maximum of 6,750 square feet. Duplexes, triplexes and quadraplexes are not only allowed but encouraged, with total square footages of up to 3,500 square feet and unit sizes as small as 800 square feet. (These are not micro-units, which tend to be under 300 square feet.)

It could be transformative, at least over many years.  Single-family homeowners can add up to two accessory dwellings per lot: one 800-square-foot ADU and one detached unit (DADU) with an 800-square-foot size limit.  Cottage clusters, or groups of small detached dwellings, are fine. These should add to the supply of housing and the type of choices available in the Portland area. Four-to-six-plexes also carry requirements for affordability and accessibility in the changes.  

It’s a big turnaround, and it’s worth watching.  Like Seattle and many young cities, most of Portland is zoned single-family and was built out in the form of suburbs with easy car commutes to the real city. That’s what WW II veterans wanted and the federal government subsidized with cheap loans and highways.

Today’s workers are different. They have shown a preference for living in urban neighborhoods and using transit, and they may not want mortgages. Yet Seattle has not adjusted, except in some token ways. The city still requires one on-site parking space per house, with the exception of accessory units in some single-family zones.  

Other cities such as San Francisco, Minneapolis, Buffalo, and Hartford have managed to drop all requirements for off-street parking, according to Michael Andersen of Sightline.org. Because it participated in formulating the changes, the Seattle think tank takes some of the credit for writing and promoting the Portland legislation, calling it a “new standard.” Portland is unique in passing a package that allows units with much smaller square footages at the same time it dropped parking requirements, he said. (Parking can be built at owner discretion.)  

Andersen expects some of the resulting units to be “naturally” affordable to people with modest incomes. Others may be subsidized in the usual ways. Some will be built by non-profits or local developers intent on affordable pricing—and the new zoning package will make it easier. At the same time, he expects the new regulations will generate revenue for parks and sidewalks, thanks to impact fees of $5,000-$14,000 per unit (based on a sliding scale). He hopes and expects Portland will see developers building efficiently, on more than one site simultaneously. Even so, Andersen expects it to be “a lifetime” before the effects of the package are truly visible. 

The recent boom has given Seattle many downtown towers and five-story apartment blocks. Incremental redevelopment, with older buildings mixed in, has given us our best urban neighborhoods. That said, there is just not enough buildable land outside of single-family zones to meet the appetite for housing. Our middle housing can only be found in a few transitional or low-rise zones. Sites are hard to find, projects don’t pencil out to be affordable, and spec developers aren’t very interested. Off-street parking is a special problem. 

In spite of all this, some Seattle architects and urban designers have made a specialty of middle range density in the heart of the city. The units are in demand, but they say zoning requirements are formidable—especially those for parking. Neighbors worry about traffic and crowding.

In Portland, the changes reverse post-war zoning, which was tinged by racism and migration fears. That old-style zoning restricted the numbers of living units, producing sprawl, and did not restrict size, producing mega-mansions. Over time, this kind of zoning resulted in some oversized houses that encroached on lot boundaries, according to Andersen.  

Eli Spevak lives in Portland with his young family, in half of a duplex on a single-family lot.  He’s a developer, contractor and long-time advocate for middle housing, a term he and others have coined. As chair of the city’s planning and sustainability commission, Spevak helped formulate last week’s single-family code changes. He expects them to survive legal challenges, partly because they are supported by the state in separate legislation that reverses single-family zoning throughout Oregon. In addition, Portland had already dropped all parking requirements for all construction within 500 feet of a transit station, and that has been transformative, according to Spevak.

The package of changes will speed a trend toward more auxiliary housing units that began nearly a decade ago in Portland and has already transformed large parts of the city. These new units, mostly tailored to existing buildings and developed by individual homeowners according to Spevak, have been encouraged with tax breaks (in the form of reduced development fees). He estimates they’re built at a rate of about one per day. Garage conversions are popular. Many have been built by homeowners who never did anything larger than a kitchen remodel. Spevak concedes that the net reduction of allowable unit sizes may drive up prices of larger houses, but this would be a small price to pay for more choice among smaller units.  Short term rentals will be encouraged, not forbidden.

Some auxiliary units have been around long enough to prove they increase the value of single-family lots, in spite of single-family homeowner fears they would have the opposite effect. Traffic and parking have simply not been an issue, Spevak says, even in inner suburbs where they leave a single drivable lane.  ADUs have been embraced because of what they do for owners and their families—allowing younger generations to live in urban neighborhoods and older ones to age in place.

Similar zoning changes in Seattle have begun to transform parts of Green Lake, Ballard and Fremont. Capitol Hill has a large share of Seattle’s middle housing because of transitional streets with low-rise height limits. But Seattle’s parking requirements bring pressures on building envelopes that can result in much-maligned skinny houses.

A package of changes with similarities to Portland’s might help to solve our housing shortage and affordability crisis. It would also be liberating for developers, renters and buyers. In the future, Seattleites might not have to choose between driveways and lawns on the one hand and apartment towers on the other. They’ll have more in the middle.  

Clair Enlow
Clair Enlow
Clair Enlow is a freelance journalist writing about architecture, planning and history. She’s a Loeb Fellow and an honorary member of AIASeattle.


  1. I’d love to see Seattle emulate most of these changes. But while I get that people hate the boxy McMansions sprouting up to replace modest bungalows, reducing the maximum size of any newly built single-family dwelling to 2,500 square feet irrespective of lot size seems very restrictive.

  2. I agree–it’s almost a slap on the hands of traditional builders and buyers. But I’m cheering for Portland because our system system is truly rigged toward two-garage standards and a politics of public involvement that excludes renters and multi-generation homeowners–at least ones who don’t want to crowd into a three-bedroom rambler.

  3. One concern about such zoning changes is what happens to the assessed value of a single-family lot that can suddenly support six units. And if that happens to my lot, does it not also affect the rest of the lots on my block? Further, if no large new houses can be constructed in Portland (though I suspect there are loopholes), does that not drive affluent folks (and their tax base) to the nearby suburbs? My last question: Is this the Airbnb Relief Act?

    • In the Oregon context, where we anchor property taxes at the time of redevelopment and then cap the subsequent annual increases at 3%, property tax changes are a non-issue for anyone who doesn’t choose to redevelop. (To the extent that this increases the redevelopment rate, which it may or may not, that means more public revenue but no effect on property taxes for other lots.)

      If this were happening in the Washington context, where property taxes are capped at the jurisdictional level with an exception for population growth, it’d also be mostly a wash because the same new options are being granted everywhere in the city. If there were property tax impacts in the WA system, it’d be on developable lots: i.e. low value structures in high-value locations. (In practice, I think these are generally home to middle-income people?) So you have to weigh the effects of that incentive to redevelop against the benefits of having additional homes in those locations.

      As for your six-unit scenario: I could be wrong, but my understanding from developers here in Portland is that unless you’re bringing in outside subsidies a la Habitat or another nonprofit houser, you’re probably not going to make enough profit on the three market-rate units to make up for the money you’re losing on the below-market units. Projects completed under this plan will probably be the same assortment of duplexes, triplexes and fourplexes that are on many older lots in prewar parts of Portland (and to a lesser extent, Seattle), before these options were banned.

      It’s entirely possible that some people who are looking for homes larger than 2,500 square feet will end up looking elsewhere. But given the nationwide drop in family sizes since the 60s, Portland and most US cities have more of a shortage of small homes than of large ones. (In Seattle, for example, 14% of homes have four or more bedrooms, but only 3% of households have more than four people.) If we don’t make attached housing and/or smaller lot sizes legal at some point, then the result over time is just going to be larger and larger and larger oneplexes … which is exactly the trend we’ve seen since bans on attached housing became widespread after WWII.

      Re Airbnb, if you think there’s going to be much market for tourism to Portland for the forseeable future, you’re more optimistic than I am! But I don’t have a problem with letting people put vacation rentals on their property as long if that’s how they finance more housing space, as long as they’re paying lodging taxes. I assume lots of former airbnbs are currently serving as extremely useful quarantine spaces right now.

      • Thanks for the helpful replies and explanations. I’m still apprehensive about unanticipated downsides from such a major change over time: loss of street parking, more transitory residents, unstable neighborhoods. I also worry that this is so aimed at the small-house market that cities may have fewer takers for the houses. Just as the Amazon market has built to single workers, not families, this seems to me to invited a similar imbalance.

  4. I’m not afraid of market distortions–there are plenty that have taken long and short-term rentals off the market. About those luxury downtown towers–for housing and hospitality–in Vancouver BC and Seattle: Even before the pandemic there were lots of dark windows, aka empty units. One interpretation of that is speculators are not even taking the trouble to rent. And condo ‘communities’ won’t have short-term rentals. Corporate expense account-driven inflation in hotel pricing has been scaring away middle-income tourists of all kinds.
    I’m for using underused resources in general, and for housing choices in particular. Pandemic aside, airbnb might be filling underused space and making hotel prices more competitive!


Please enter your comment!
Please enter your name here

This site uses Akismet to reduce spam. Learn how your comment data is processed.

Comments Policy

Please be respectful. No personal attacks. Your comment should add something to the topic discussion or it will not be published. All comments are reviewed before being published. Comments are the opinions of their contributors and not those of Post alley or its editors.