Why single stairs work everywhere but here

The fire codes point is real, but I'd push back slightly on the "nobody wants to fight" part—it's actually harder than that. There's a genuine path-dependency problem baked in, and it's worth understanding why Europe and North America diverged in the first place. Europe's postwar rebuilding happened under real scarcity. You couldn't afford to waste floor area on redundant stairs, and you had to rebuild fast. So they optimized for density and accepted fire risk with compensating measures—better suppression, shorter corridors, regular inspections. North America, meanwhile, was building from a position of abundance (cheap land, cheap timber, labor willing to build taller) and had access to the early sprinkler patents. But the codes that got written reflected something deeper: a cultural instinct toward over-engineering safety once you could afford it. It wasn't paranoia exactly—there were genuine multi-building fire disasters in the 1950s that spooked building officials—but it did lock in a "redundancy good, density expensive" logic that now persists even when the original conditions don't apply. The sticky part isn't just firefighters' unions (though they're part of it). It's that codes have been written so that developers and architects have designed entire business models around them. A contractor in Toronto in 2024 doesn't even *think* about the five-story option because the code-cost ratio means it never pencils. The path dependency is almost invisible from the inside. You'd need someone to actually try building that way and prove it works before the psychology shifts, which creates a chicken-egg problem that regulation alone won't solve.

The codes won't change because the people who'd benefit most from change have no constituency. Developers would build the mid-rise if it penciled—they already want to maximize land value—but scattered individual projects fighting local code is a tax on their time and legal budgets. The firefighters' union isn't even the main issue; it's that once you start carving exceptions, you've admitted the rule was arbitrary, and that opens you to liability if something goes wrong. A fire in a five-story walkup with a legal variance attached becomes a referendum on whether the variance was the problem. No city wants that exposure. So what'll actually shift this is when the housing crisis forces a state or provincial government to impose code from above. Not because they're convinced on the merits—they'll still hedge with sprinkler requirements and corridor length limits—but because single-family zoning and parking minimums became politically toxic enough that mid-rise parking requirements look reasonable by comparison. You'll see it happen piecemeal: Vancouver or Montreal or some mid-size Rust Belt city gets desperate enough to pass a blanket code change, it doesn't burn down, and then other cities copy it five years later. But it takes crisis, not argument.

There's actual empirical work on this. Glaeser and Nathanson's 2017 paper on zoning and housing supply found that building code stringency (which they measured partly through egress requirements) explained a meaningful chunk of the variation in housing density across US metros—larger effect than explicit height restrictions in some cases. They had to dig into the technical codes because most people, including policymakers, don't realize these requirements exist or how binding they are. The fire safety argument does shift under sprinklers, but the evidence is messier than "sprinklers solve it." Sprinkler effectiveness depends on maintenance, water pressure, and occupant behavior in ways that single-staircase designs in older European buildings don't need to. That said, you're right that code stickiness is real—Ortalo-Magné and Prat studied this in France and found that when they loosened certain density restrictions in the 1990s, it took 15+ years for the building stock to actually respond because developers had already structured around the old constraints. Codes become invisible assumptions in financing and development practices. The union angle is speculative though. What I'd want to know is whether fire codes are actually driven by firefighter preferences or whether they're just path-dependent—written in an era of worse sprinkler technology and never revisited. The stickiness might have less to do with political power and more to do with the fact that changing them requires municipalities to re-litigate fire safety from first principles, which is expensive and risky politically.

I'd push back on the fire code being the main culprit here, or at least the whole story. Chicago's had two-staircase requirements since the 1890s—actually stricter than most places now—and it still managed to build genuine mid-rise fabric through much of the 20th century. Brownstones, courtyard buildings, modest apartment blocks in the five-to-eight story range. The codes didn't *prevent* them; developers just built them anyway because the economics worked and zoning allowed mixed-use streets. The real divergence isn't fire codes, I think. It's zoning. Once North American cities started separating uses and mandating parking, and once single-family zoning became the default for residential areas, the mid-rise market evaporated. You can have perfect egress laws but if the only legal place to build mid-rise is downtown and land there costs $2M per lot, you're still going to choose either the three-story wood-frame building (cheaper land, residential zone) or the fifteen-story tower (justifies expensive downtown land). The fire code didn't kill the five-story building. Euclidean zoning and parking requirements killed it. The fire code just made it slightly less profitable once you already weren't allowed to build it in 90% of the city.