Key takeaways
- Portland, Oregon’s 2020 zoning reform opened single-family neighborhoods to “middle housing,” allowing up to four units by right.
- Incremental infill development, including backyard cottages and small multiplexes, has driven modest density growth in Portland, with more than 1,400 accessory dwelling and middle-housing units permitted since 2021.
- Multiplexes and ADUs are commonly found on oversized single-family lots where the main residence has deferred maintenance, said Neil Heller, a zoning consultant who worked with the Oregon city.
About six years ago, roughly 75% of Portland, Oregon’s residential zones were single-family only, and several of the others were historic. That’s quite the bind for a rapidly growing municipality in the middle of a housing crisis.
“Where there was multifamily, most of that zoning had been pushed far out to the edge of the city,” said Neil Heller, principal of Neighborhood Workshop, a zoning consultancy. “So, there's a huge equity disparity in where building was allowed to happen.”
But in 2020, the Pacific Northwest city overhauled its zoning code, allowing for multiunit housing in those neighborhoods once limited to single-family structures. Portland had taken it further than a 2019 statewide measure that allowed duplexes in single‑family zones in cities with more than 10,000 residents. Under its Residential Infill Project, the city opened the door to smaller duplexes and triplexes — up to four units by right and as many as six on larger lots if half were designated affordable.
“It has a real unfortunate acronym,” Heller pointed out. “RIP.”
Still, it was the kind of interstitial development Heller had advocated for over the years. He’d started as an urban designer, laying out expansive master plans. But during the 2008 Great Recession, that kind of work evaporated, leaving Heller focused on the small stuff.
“What's the smallest thing we can still do despite not having finance?” he told Homes.com News. “So, I got really interested in these real small sort of incremental-type ideas.”
The definition of "incremental" ranged, but it focused Heller on a local level, ultimately connecting him with the Incremental Development Alliance, a national nonprofit that helps people invest in their neighborhoods and communities. Heller also ended up going back to school, getting his planning degree and becoming a zoning consultant who helps cities around the country update their codes on a small scale, favoring an “infill-based approach,” he said.
Projects pop up on oversized lots with deferred maintenance
When it came to Heller’s own city of Portland, he was already invested in updating the residential zoning code from an advocacy side, where he underscored the value he saw in infill residences. From there, he worked as a zoning consultant to help make an affordability bonus pencil out for the rezoning, allowing developers to build up to six townhouses on a lot if some of them were deemed affordable.
“We did the math to understand what level of bonus an affordable housing developer would need to compete with the private market for the same piece of land in a high-amenity neighborhood,” he said, “because our affordable housing developers were also getting gentrified out, looking further and further out for cheap land.”
While the initial proposed policy permitted four units by right with two bonus ones, if affordable, then its final iteration, it required half to be so.
“So, you actually lost one of your market-rate units, and it changed the math considerably,” Heller said. While some projects have been completed using the affordability bonus, it hasn’t been embraced en masse, he noted; it’s still hard to make things pencil out.
Still, a number of infill cottages and multiplexes have gone up in the city, with more than 1,400 accessory dwellings and "middle housing" units permitted between August 2021 and June 2024, according to the city. Oftentimes, Heller noted, that backyard infill happens on an oversized lot that can fit two or three compact cottages.
“It's usually a house that maybe has some deferred maintenance,” he said. “And then it gets sold and picked up by a local developer who renovates the house and then adds the new homes in the back.”
The following interview has been edited and condensed for clarity.
What was different about this rezoning process, from your perspective?
Going to Planning Commission and City Council meetings and testifying used to be the domain of retirees with a lot of time on their hands, who, you know, were sort of opposed to these ideas. But through this process, the city embraced a big-tent approach. Lots of organizations got involved — people who cared about housing and affordability, people who cared about transportation, people who cared about trees — all came under a single banner to sign on to these ideas, saying, “No, we need more density for all these reasons.”
It became kind of the cool thing to show up to a testimony prep meeting and have pizza and maybe a drink with a bunch of like-minded people. Then you had young people showing up at council, and you had renters start showing up at council, saying how important these changes were to them.
Are there any common misconceptions you encounter when it comes to Portland’s rezoning?
Yeah, to this day, people will go online and say: “What's going on with all these new houses? They're not even affordable. They promised that they would be affordable.”
I guess it's just what your frame of reference for affordability is, but there are different levels of affordability. Our frame of reference is that it is affordable relative to what used to be allowed, which is a single-family house — and a new construction single-family house built today sells for $900,000.
And if we can build a detached house under this new sort of zoning regime and sell it for anywhere from $380,000 to $400,000-some, that’s less than the single-family house. It’s within the range of people earning the median income.
So, when we're talking about those affordable units on a lot, are those income-restricted?
There are no deed restrictions. They are just inherently a lower price, largely because of the trade-off in housing and yard size. Oftentimes, there's also no parking.
So, there are some trade-offs there that the market just isn't going to pay a lot for. Then, because of the density of the land use, it pencils for the developer while also providing homes at a lower cost. So, both sides win.
Portland is generally seen as a liberal city, but how do you win over communities as you're reworking these zoning and building codes to allow for denser neighborhoods?
Interestingly, the more liberal communities tend to be more emphatically against this kind of idea, largely because I think they have roots in the environmental movement dating back to the '70s, and so many of them are concerned about losing yard space and what happens to our urban fabric if there’s less nature.
In Oregon, we have urban growth boundaries around our cities. And if we don't infill, we're going to put pressure on those urban growth boundaries to expand into what is real nature — real forests. So, it's kind of a trade-off: Do we want to spread out? Do we want to do the Houston-style sprawl across the landscape? Or do we want to try to keep things compact?
And for people who are worried about density infringing on property values or weighing on existing infrastructure, how do you walk people through those elements?
So, existing infrastructure — I mean, that's a real thing. Some places can't handle it, and that's fair. But you’ve got to think about the rate of change. We've been able to do this now for six years, and it's not like this massive change where whole neighborhoods are totally changed. The rate of change is modest, and I think that over time, you know, ideally, that's how cities grow.
The property value thing is interesting because values are typically driven by land, which is driven by competition. So, if you are adding homes to a neighborhood, you're adding a certain level of density that can then support neighborhood amenities. I call it livable density — it's enough density to support these amenities close by so that your neighborhood becomes attractive.
I think it has a tendency probably to increase your property values because people will want to live there, and there’ll be competition.
I think it does increase vitality in a neighborhood.