The staircase rule that’s limiting housing growth

Across the United States, policymakers are rethinking how zoning affects housing supply, and a growing number of states are enacting reforms to make it easier to build. Yet, one area of regulation remains largely untouched and rarely questioned in public debate: the building code. Because building codes are closely associated with safety, revisiting them often feels uncomfortable. Their purpose is to protect life and property, though many of their underlying provisions date back nearly a century. The modern International Building Code, which most states and cities rely on, was first published in 2000, yet its foundations rest on safety conventions developed in the 1930s. In a world where construction materials, engineering methods, and fire prevention systems have all transformed, it is worth asking whether rules written for another era still make sense today.

Among the most influential yet overlooked aspects of the building code are its egress, or exit, requirements. In most jurisdictions, apartment buildings above three stories must include two separate staircases to allow occupants to evacuate during a fire. This rule originated in the early 20^th century, when fire spread rapidly through wood-frame structures and safety systems such as sprinklers and smoke containment did not yet exist. While the intent remains sound, ensuring safe escape during emergencies, the rule’s rigidity now limits the kinds of multifamily housing that can be built, particularly smaller and mid-rise apartments that fall between single-family homes and high-rise towers.

Although it may appear that revisiting these safety standards means trading safety for cheaper or easier construction, that is not the case. Modern building practices have advanced far beyond what older codes account for, and most developers are constructing safer buildings than ever before. Nearly all new multifamily projects include sprinkler systems, smoke detectors, pressurized stairwells, and fire-resistant materials that significantly reduce the risk of smoke, which remains the greatest danger associated with stairwell safety during a fire. Compartmentalized floor plans and automatic suppression systems further limit exposure and contain flames within a single unit. Research consistently shows that the number of staircases in a building is far less predictive of safety outcomes than the presence of these systems, which are now standard features in contemporary construction. This means that older, still-in-force regulations requiring multiple stairwells are less effective and redundant in light of new practices. Such redundancy leads to higher costs and fewer dwelling units than could be accomplished with more up-to-date requirements.

Many developed nations reflect this same understanding in their building codes. Countries such as the United Kingdom, Canada, France, Germany, and Australia permit single-stair residential buildings well above the U.S. height limit of three stories, with research finding no higher fire-related risk. Canada, for example, allows such buildings up to six stories, while France permits them up to 16 stories, yet both maintain lower residential fire fatality rates than the U.S. The United States records roughly 1.1 residential fire deaths per 100,000 people, compared with 0.5 in the United Kingdom and 0.4 in Canada, despite their more flexible egress standards. This disparity in fire-related deaths suggests that comprehensive fire-safety strategies such as sprinklers, pressurized stairwells, and smoke containment are the true determinants of safety outcomes, not the number of staircases a building contains.

Design, livability, and housing supply

Revisiting the two-stair requirement could also improve spatial efficiency and expand housing options. A second staircase consumes valuable interior space, often lengthening corridors and reducing the number of possible apartments per floor. Further, when this constraint is removed, developers can construct dual-aspect units (apartments with windows on two sides), enhancing natural light, airflow, and livability. In one modeled comparison, the single-stair design accommodated 10 apartments per floor compared with nine in the two-stair version and provided six wheelchair-accessible units instead of four. The freed space can be used in different ways, whether for additional units, larger floor plans, or improved features and amenities, depending on how developers choose to design the building. This design flexibility also allows for a greater range of apartment types, including family-oriented two-, three-, and four-bedroom units, within a compact footprint.

Studies also indicate that single-stair mid-rise buildings with compact floor plates can reduce total construction costs by roughly 6% to 13% compared to similar dual-stair designs, further improving their financial viability.

From a policy standpoint, these design efficiencies can make development feasible on smaller or irregular infill lots, specifically the sites often left vacant in urban areas due to design restrictions. Grouping minimum lot size reform, density reform, and reforms allowing single-stair layouts could facilitate mid-rise “missing middle” housing—three- to six-story buildings that bridge the gap between single-family homes and large apartment complexes. Such buildings tend to integrate more harmoniously into existing neighborhoods while providing attainable homes near transit and employment centers.

Importantly, the discussion around affordability should recognize that cost savings derived from code flexibility can directly influence project feasibility. Reducing excessive internal space requirements does not compromise safety and allows resources to be reallocated toward quality finishes, energy efficiency, or additional units. Developers respond to both the profit motive and the cost structure imposed by regulation; adjusting those structures can stimulate new housing production at little to no cost to the taxpayer without direct subsidies.

Policy reform momentum and a balanced path forward

A growing number of jurisdictions are beginning to reexamine building codes through this lens. Seattle updated its building code in 2024 to allow single-stair buildings up to six stories when equipped with sprinklers, pressurized stairwells, and limited evacuation distances. Hawaii and Washington, D.C., are conducting similar studies, and New York City has initiated a review of its egress standards in light of advancements in suppression and smoke-control systems. These reforms reflect a shift toward performance-based regulation, where compliance is measured by safety outcomes rather than by prescriptive design rules.

Critically, reform efforts are proceeding with caution. Policymakers and fire-safety experts emphasize that single-stair layouts should remain limited to mid-rise buildings with comprehensive safety systems and robust construction materials. Evidence supports this threshold: both international practice and empirical testing indicate that buildings within this height range (three- to six-story buildings) can maintain safe egress conditions during fire events when modern systems are present.

Understanding that the greatest fire risks occur in older, noncompliant buildings reframes the debate. Encouraging new construction under contemporary codes not only adds housing but also improves safety overall by replacing aging, higher-risk structures. Updating the egress standard retires old, out-of-date rules that no longer enhance safety with proven modern safety engineering that also serves public needs for housing.

Building codes interact with zoning, permitting, and infrastructure requirements to shape the feasibility of new housing. When outdated internal standards persist, they inadvertently restrict production and inflate costs with no added benefit to anyone. Modernizing these codes allows cities to respond to both safety expectations and affordability challenges with equal rigor—an approach that’s both smarter and safer. Ultimately, the single-stair discussion is part of a broader movement to align building regulations with current technology and housing demand. The data show that under modern safety systems, single-stair mid-rises achieve comparable safety performance to traditional two-stair buildings simply through codifying already-standard practices. Updating the code to reflect that reality would not only encourage innovation but also ensure that new homes are built to the highest contemporary standards of safety, design, and livability.

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