Legislative Updates: Single-Stair Housing

Ever heard of "single-stair" buildings? If not, you're not alone. Until recently, this was inside-baseball among architects and housing advocates - the kind of thing that came up at conferences and stayed there. But there's now real legislation in play to expand which buildings get the single-stair treatment, and correspondingly lower costs.

How it is Now:

Most buildings are required to have two stairwells, with one long-standing exception: 3-story buildings with up to 4 units have always been allowed just one. That two-stair rule was written in response to periodic fires in old housing stock, and it hasn't gotten a serious second look in a century. Meanwhile, building safety has leveled up dramatically, with full-building sprinklers, fire-rated floors, walls, ceilings, and roofs making modern buildings a different beast.

How it COULD be:

So California is asking the natural next question: why not expand the old exception to taller buildings with more units? Lose the second stairwell, shorten the corridors, and suddenly construction is cheaper, and you can fit more units in the same footprint. The architecture community is pushing for single-stair buildings up to 6 stories, estimating cost savings of 6%-13% with the change. Between that, the housing crisis, and construction costs going through the roof (so to speak), the idea has serious momentum.

And that momentum has been showing up in real places. Culver City became the first (and only) California city to greenlight single-stair buildings up to 6 stories, passing the legislation on Sept. 29, 2025, right before the statewide freeze on local building code amendments went into effect. In SF, Mayor Lurie brought in an MIT think tank to dig into it, and he, several supervisors, and the Planning Commission are all on board. Seattle has been doing this since the 1970s, and seven other US states passed similar single-stair legislation in 2025, including Colorado, Texas, Montana, and New Hampshire.

All Hail New Legislation:

Given the statewide freeze, however, no other California cities can act until the State Legislature does. Assembly Member Alex Lee introduced AB 835 back in 2023 to increase the allowable single-stair buildings, but the California Professional Firefighters union successfully pushed to amend it down from a code change to just a research report. The report landed in March 2026, two months past its original deadline, and recommended capping single-stair buildings at four stories instead of six. This would only allow an increase of 1 story from current Building Code limits, so it’s not much of a gain.

His current bill, AB 2252, co-authored with Assembly Member Buffy Wicks (Oakland) and State Senator Scott Weiner, would direct the state housing department to develop building standards for single-stair multiunit residential buildings up to six stories, for inclusion in the next California Building Standards Code CA. The ball is squarely in Sacramento's court. AB 2252 is moving through committee hearings, and the State Fire Marshal will ultimately need to be convinced.

With a real bill in motion, mounting national precedent, and a housing crisis that isn't getting any smaller, this feels like the closest single-stair has ever come to actually crossing the finish line. Fingers crossed — more homes, lower costs, and fewer hoops would be a win all around.

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