Single-stair reform and the doldrums of implementation

At Miter, we’re painfully aware of how much the rules governing construction shape our built environment. This piece, part of an ongoing series on regulatory friction in the construction industry, looks at the successes and frustrations of a seemingly small area that’s ripe for reform: height limits for single-staircase buildings.

In 2023, as he cleaned out his college dorm room ahead of graduation, Julian Frost fired up a podcast, a 13-parter called The Livable Low-Carbon City. 

Frost just wanted to pass the time, but the podcast’s first episode, on staircases in apartment buildings, turned out to be a spot-on postscript to his college career. The Baltimore native had written a thesis about health-focused urban design in postwar France. In the city of Nantes, he had spent time in well lit and well ventilated apartments, arranged around a single staircase, that made the buildings back home feel like bunkers. 

The podcast explained how U.S. building codes require that developers fit two staircases into multi-family projects taller than three stories, resulting in drab and expensive-to-build apartment blocks. The second stairway can account for up to 13 percent of construction costs, according to one study.

But what if the single staircase were possible beyond three stories, as it is in Europe? What would our cities look like then? 

“Once I understood the concepts, it all just clicked into place,” Frost said.

Frost graduated, and decided to bring what he’d learned about the building code back home. He wrote blog posts, emailed elected officials in Baltimore, and got in the weeds with anyone willing to hear about single-stair reform. 

Frost says that at times he “probably sounded insane,” but if he was insane, he had good company. Advocates and policy wonks had identified single-stair reform as a small adjustment to the building code that could have significant effects on the sustainability, livability, and construction costs of multi-family housing in the U.S. In the last five years they’ve made a difference, with cities across the country (including Baltimore) working to extend height limits for single-stair buildings. 

But with their success, the reformers have entered an even tougher phase of their project. They’re learning that just because something is legal doesn’t mean it’ll get built.

The case for single stair reform

Local building codes in North America – the rules that shape everything from kitchen layout to elevator width – derive from the International Building Code, a codebook updated every three years by the nonprofit International Code Council. 

The ICC creates model legislation, and derives its legitimacy from the fact that most cities in the U.S. and Canada adopt it without question. Its studies, which researchers criticize as unscientific, justify many typical features of the urban environment. 

Two people have led the movement to question those justifications: Michael Eliason, a Seattle-based architect and narrator of the podcast that inspired Julian Frost, and Stephen Smith, founder of the nonprofit Center for Building in North America. 

Inspired by Eliason, Smith started his organization because no one else was taking the time to understand all the little rules that determine what’s cost-effective to build, and therefore how we experience our cities. Before long, it was clear that his first target for reform should be height limits for single-stair buildings, which, he says, are based on outdated concerns over fire safety. Smith says that for a four-story building, the code-compliant second staircase can be 10 percent of the total construction cost.

“Developing really is a block-by-block knife fight for small amounts of money,” he said. “But 10 percent is a lot of money.” 

At a time when pretty much every U.S. city could use more multi-family housing, Smith and others argue that allowing taller single-stair buildings would make those units way more cost-effective for developers and contractors. 

It could also be the death blow for the double-loaded corridor, a feature of the modern U.S. apartment block that urbanists from across the land invoke with grief and disgust. The two-staircase requirement often necessitates a rectangular building in which the landings on each floor are connected by a long hallway – “what people in other countries think of as hotels,” Smith notes in a policy brief. This corridor is “double-loaded” by virtue of the apartments that line each side of it. 

The design means less light and ventilation for residents (each apartment only has window access via one wall), and long, narrow floorplans, the result of the developer maximizing rent.

Smith has documented efforts to enact the single-stair fix with an interactive reform tracker. The map-based tool shows developments from California to New York, but the reform that Smith says he’s proudest of is in Minnesota. 

It demonstrates both the enthusiasm behind the single-stair movement and the difficulty of converting that energy into lasting changes to the built environment.

Minnesota tests the safety argument, and reformers win

Like Julian Frost, Cody Fischer of Minneapolis remembers his introduction to single-stair reform as a sort of conversion, and at the hands of the same high priest. 

“I got single-stair-pilled like four years ago, following Mike Eliason, of Larch Lab in Seattle, in his social media quest,” Fischer said. 

As a developer who builds low-carbon multi-family projects, it was only natural that Fischer would embrace a design fix that could bring more natural light and ventilation to his buildings. Tall, single-stair apartment buildings would also improve the density of predominantly single-family neighborhoods in the Twin Cities. Unlike double-loaded apartment buildings, you can fit them on the single lots available for infill development. 

“It’s almost impossible to assemble land in those types of locations, and it’s extremely expensive, so you get the status quo,” Fischer explained. “Unless you make it possible to do single-site development. And that’s where the single-staircase building comes in.”

Along with Smith, Fischer helped convince state lawmakers to propose a bill that would adjust the building code. The bill was diluted into a $225,000 allocation for a fire-safety study — the price, Smith likes to point out, of one stairway in a small multi-family building — but they’re hoping the results are too clear for lawmakers (and developers) to ignore.

“It was decisive,” said Fischer. 

The study showed that during a fire in an eight-story single-stair building, the risk of egress being blocked would be less than in a double-loaded corridor. In other words, the single-stair building, non-compliant because of fire concerns, might actually be safer in a fire. In a 2025 report about the safety record of single-stair buildings in New York City, Smith and co-authors at The Pew Charitable Trusts came to similar conclusions. 

Fischer and Smith have also worked with staff in Minnesota’s Department of Labor and Industry to make a more modest code change — to allow single-stair buildings up to four stories — that by all appearances will take effect this year. But the market doesn’t seem ready.

“All of us little guys are really excited,” said Fischer. “But the larger developers in the Twin Cities metro…I don’t think any of them are even aware of this debate.”

Changing the code isn’t changing what gets built

In Baltimore, this has been a sobering lesson for Frost. 

On the one hand, he and fellow reform advocates in Maryland have had unequivocal success. The state has directed its labor department to conduct a single-stair viability study. This past November, Baltimore amended its building code to allow single-exit apartment buildings up to six stories (though the six-story limit is only for buildings made with non-combustible materials, which Frost and others admit will be a project-killer for many).

On the other hand, what good is single-stair reform if builders don’t take advantage of it? Frost wants to think about how code reform could enable more residential construction on large lots. But he’s also realizing that Baltimore’s sluggish small-lot growth won’t just go away because the building code was adjusted. 

“There needs to be more outreach and engagement even to have developers understand what’s possible now on small lots,” he said. 

Last year, between working his day job and running his blog, Frost organized a design competition for Baltimore-based architects. He scheduled it in the lead-up to the City Council’s vote on the six-story limit. Per the contest guidelines, each submitting team would propose “a mid-rise single-stair residential building on a small infill lot of their choice in Baltimore City.”

Frost recalls a developer in the audience asking about one of the proposals, a building on West Baltimore Street. She said she wanted to build it. When, she asked, would that be possible?

“There clearly are developers,” Frost said. “I would just love if there was a way that all of them could be centralized.”

Willing developers exist, even where reform lags

Frost is obviously right — the developers are out there. And they might be easier to find than he assumes. 

Oz Erickson has been doing large-scale multi-family development in San Francisco since 1979. The Emerald Fund, of which he’s chair, has developed more than 5,500 housing units in its tenure, according to its website. It focuses on infill in a city that’s notoriously difficult to build in. It’s exactly the sort of multi-family developer that Frost, Smith, and Fischer say need to get with the single-stair program. 

Erickson has faced pretty much every barrier there is to housing construction in San Francisco. He explains why so many projects don’t pencil with a weary insistence. He’s probably well aware of how the little things – like installing toilets – can add up.

But even from his position in California, where building code reform is lagging behind places like Minnesota, Maryland, and Tennessee, he’s optimistic.

When asked if any policies would make housing construction easier in his city, he answered without hesitation: