California YIMBY Statement on Future Proposed Draft Recommendations for the State Fire Marshal Single-Stair Study
October 2025
On behalf of California YIMBY, I respectfully submit the following comments on future proposed draft recommendations for the State Fire Marshal’s Single-Stair Study.
California YIMBY is a statewide housing policy and advocacy organization that focuses on making our state a more affordable and sustainable place to live, work, and raise a family. Our work focuses on reforming state housing policy to make it faster, easier, and less costly to build housing in communities across the state; we also pay close attention to effective implementation of these policies at the jurisdictional level. Our core values include advancing housing affordability, sustainability, and equity while ensuring that all Californians have access to safe, well-designed homes.
We commend the Office’s continued commitment to public safety and its careful consideration of building code reforms. Enhancing and advancing fire safety, at the building, landscape, and community levels, is an urgent task for our state. We also agree that any changes to existing fire safety codes should remain laser focused on enhancing and improving the safety of our built environment, and, whenever possible, correcting existing vulnerabilities or flaws.
It is with this framework and these values in mind that we submit these comments. We believe that the inclusion of additional evidence could substantially improve the conclusions and lead to both safer buildings, and more affordable homes – two goals which are not mutually exclusive; we believe both goals should be at the center of consideration.
Single-stair buildings were included in this dataset and were found to be just as safe as their dual-stair counterparts, due in large part to the redundant life-safety systems required in contemporary codes.
We urge the Office of the State Fire Marshal to include the evaluation of six-story single-stair buildings within the scope of the draft report. This height standard, which has been adopted as a part of single stair regulations in other U.S. states with high exogenous fire risk, reflects current best practices and aligns with both existing code precedent and the demonstrated capacity of California’s fire services. We also believe it is appropriate to apply differentiated conditions at varying heights, and to examine evidence that there are viable mitigations that can safely extend current three-story allowances to buildings of four or more stories.
One widely accepted mitigation is limiting single-stair floor plates to approximately 4,000 net habitable square feet with no more than four dwelling units per floor. By contrast, under California’s current code, a sprinklered Type III-A building with two exit stairways may reach nearly 96,000 square feet, often accommodating 25+ units a floor, a vastly larger scale. We suggest that the Office should consider middle pathways that recognize safety can be achieved between these two extremes of habitable density.
The International Code Council’s Means of Egress Committee has already recognized this distinction. At its 2024 hearing in Long Beach, the Committee voted to approve a modification to the E24-24 proposal, allowing single-stair apartment buildings up to four stories in the forthcoming 2027 International Building Code. This model language is designed for adoption nationwide, across jurisdictions with varying levels of fire service capacity. California should, at a minimum, align with these evolving national standards.
It is essential to evaluate single-stair proposals in context, not against hypothetical two-stair buildings of the same size. In practice, single-stair buildings are far smaller and house significantly fewer residents per stairway than large, double-loaded corridor buildings allowed under current code. Indeed, the California Building Code permits two-stair double-loaded corridor designs with occupant loads that may exceed 100,000 square feet per story, far greater than any six-story single-stair building would house in total.
Recent research reinforces both the safety and policy rationale for reform. Two separate Pew Research analyses found that modern multifamily buildings constructed after 2010 are fifteen times less likely to experience fatalities than those built before 1999 (0.5 deaths per million versus 7 deaths per million). This finding underscores that modern construction standards, regardless of local fire department capacity, have dramatically improved life safety performance. Notably, single-stair buildings were included in this dataset and were found to be just as safe as their dual-stair counterparts, due in large part to the redundant life-safety systems required in contemporary codes.
A separate Pew analysis also found that single-stair buildings cost 6% to 13% less to construct and enable more affordable, small-scale, infill development. Likewise, the Harvard Joint Center for Housing Studies reported that these buildings dedicate 10% more floor area to living space, rather than hallways, improving both cost efficiency and livability. These findings demonstrate that single-stair buildings are not only safe, but also a proven strategy to expand affordability and foster community-oriented design.
Given California’s twin goals of enhancing both safety and affordability, these findings should be reflected in California’s building code policies.
Additional technical research supports these findings. A study by LMDG Fire Safety Consultants for the City of Edmonton determined that egress in single-stair buildings with pressurized stairways would require five concurrent failure conditions to be compromised, versus seven for dual-stair configurations. Notably, two-stair buildings in California are not required to have pressurized stairs, demonstrating that existing single-stair mitigation strategies already meet or exceed equivalent safety performance.
Concerns about fire service capacity are also misplaced when applied uniformly across California. Many jurisdictions, including Seattle, New York City, Honolulu, and others, have adopted single-stair allowances precisely because their codes ensure buildings are self-reliant through sprinklers, alarms, and smoke control. California has many well-resourced municipal fire departments that are more than capable of managing the same conditions.
Finally, if the Office of the State Fire Marshal elects to recommend against permitting single-stair buildings beyond three or four stories, we urge that such a recommendation be accompanied by a comprehensive, evidence-based justification. This should include comparative data explaining why jurisdictions such as Seattle, New York City, Austin, Honolulu, Montana, Vermont, Georgia, Minnesota, and others, along with the forthcoming International Building Code have found these buildings to be safe, while California has not.
California YIMBY stands ready to work with the Office of the State Fire Marshal and other stakeholders to develop balanced, data-driven code language that ensures life safety while addressing our state’s urgent housing needs. The opportunity before us is not to preserve outdated assumptions, but to create a framework that aligns modern fire protection standards with the realities of building design, affordability, and urban form.
M. Nolan Gray
Senior Director of Legislation and Research
California YIMBY
Eduardo Mendoza
Metropolitan Abundance Project Research Associate
California YIMBY
Send in a Comment on the State Fire Marshal’s Single Stair Study
The public has an opportunity to provide comments on the draft report, and we want to make sure the State Fire Marshal hears from YIMBYs loud and clear: let's keep California at the forefront of sensible building code reform!