The Single-Stair Revolution: How States Are Rewriting Building Codes to Unlock Affordable Housing

For decades, the conversation around the American housing shortage has focused on zoning laws, interest rates, and the cost of lumber. But a growing coalition of architects, urban planners, and policymakers has identified a more obscure culprit hiding in plain sight: the municipal building code. Specifically, the intense focus is now on a seemingly mundane regulation that dictates how people exit a building. Across the United States and Canada, almost any residential building taller than three stories is legally required to have at least two separate staircases. While originally conceived as a non-negotiable life-safety measure, a wave of new research and legislative momentum in 2026 suggests this requirement may be an outdated relic that is artificially strangling the supply of affordable, family-sized apartments. The movement to rethink this rule—known as single-stair reform—is rapidly reshaping how cities approach urban density.[5]

To understand why a staircase mandate dictates the shape of a city, one must look at the architectural geometry it forces developers to use. When a building code requires two means of egress, architects are essentially forced to connect those two stairwells with a long, central hallway. This layout, ubiquitous in North American apartment complexes and hotels, is known as a double-loaded corridor. Because the hallway runs down the middle of the building, apartments are slotted in on either side. This configuration fundamentally limits how a building can be designed and, more importantly, where it can be built. A double-loaded corridor requires a large, wide footprint, meaning developers must acquire massive parcels of land to make a project financially viable.[1]

The spatial demands of the double-loaded corridor effectively outlaw the development of missing middle housing on small, urban infill lots. In dense neighborhoods where land is scarce and expensive, a developer might find a narrow, vacant lot perfectly sized for a six-unit apartment building. However, once the architect factors in the space required for two separate stairwells, an elevator, and a connecting hallway, the remaining square footage for actual living space becomes too small to justify the construction costs. As a result, these small lots remain empty, or they are developed into luxury single-family mansions, exacerbating the housing shortage in highly desirable, transit-rich neighborhoods.[1]

Beyond the macroeconomic impact on housing supply, the two-staircase rule severely degrades the quality of the apartments that do get built. In a double-loaded corridor building, each apartment only has windows on one side—the exterior wall facing the street or the alley. This creates deep, bowling alley style floor plans where the front door opens into a dark kitchen, and the only natural light is found at the far end of the living room. Because windows are limited to a single facade, cross-ventilation is physically impossible, making the units harder to cool passively. Furthermore, to maximize the number of units along the hallway, developers prioritize narrow studios and one-bedroom apartments, making it incredibly difficult for families to find three- or four-bedroom units in urban centers.

The alternative to this North American standard is known internationally as the point access block. In a point access block, a single central staircase and elevator core serve a small cluster of apartments on each floor—typically two to four units. Because there is no long central hallway dividing the building, the apartments can span the entire width or corner of the structure. This allows for windows on two or even three sides of the unit, flooding the space with natural light and enabling genuine cross-ventilation. This architectural style is not a radical new experiment; it is the standard method of building mid-rise apartments across Europe, Asia, and Latin America, where single-stair buildings of six to eight stories are entirely routine.[5]

The financial implications of transitioning to point access blocks are profound. Constructing a second, fire-rated stairwell in a mid-rise building costs approximately $200,000, not including the ongoing maintenance and the massive loss of leasable square footage. By eliminating the redundant stairwell and the sprawling corridors, developers can reduce overall construction costs by 6 to 13 percent for a four-to-six-unit building. In a housing market paralyzed by high interest rates and soaring material costs, that margin is often the difference between a project breaking ground and being abandoned. Proponents argue that these savings can translate directly into lower rents and more accessible homeownership opportunities for middle-income families.[4]

Armed with this economic rationale, a bipartisan legislative wave has swept across the United States. In 2024 and 2025, states including Colorado, Tennessee, Texas, and Montana passed landmark laws allowing single-stair multifamily buildings up to five or six stories. Colorado's legislation, for instance, mandates that municipalities with populations over 100,000 update their building codes by December 2027 to permit five-story single-stair developments. Tennessee took an opt-in approach, resulting in major cities like Memphis, Knoxville, and Chattanooga rapidly adopting the reform. By mid-2026, over 1.1 million Tennessee residents were living in jurisdictions that had legalized point access blocks, signaling a massive shift in regional planning.[4]

The momentum has continued to accelerate into 2026, reaching regions historically known for strict regulatory environments. In February 2026, Massachusetts Governor Maura Healey signed an executive order establishing a technical advisory group to facilitate safe and affordable single-stair residential buildings. The order explicitly recognized that current building codes limit the feasibility of mid-size residential construction and called for evidence-based updates to the Massachusetts State Building Code. This move by a major coastal state highlighted how single-stair reform has transitioned from a niche urbanist talking point into a central pillar of mainstream gubernatorial housing policy.[3]

Despite the clear architectural and economic benefits, the single-stair revolution faces a formidable hurdle: the deeply ingrained culture of fire safety. The North American mandate for two staircases was not born out of malice, but out of historical tragedy. In the late 19th and early 20th centuries, catastrophic tenement fires in cities like New York claimed thousands of lives, largely because residents were trapped in combustible buildings with only one wooden staircase. These disasters led to the widespread adoption of the external fire escape in the 1860s and, eventually, the strict two-staircase mandates that define modern building codes. For generations of fire marshals, the concept of a single exit has been synonymous with a death trap.[5]

Fire safety traditionalists, including representatives from the National Fire Protection Association and various firefighter unions, have expressed valid concerns about the speed of these legislative reforms. Their primary argument centers on the principle of redundancy. In the event of a severe fire, if the primary stairwell becomes compromised by smoke or flames, residents in a single-stair building have no alternative route of escape. Furthermore, a single stairwell must simultaneously serve as the evacuation route for panicked residents and the primary staging area for heavily equipped firefighters moving upward, creating the potential for a dangerous bottleneck.[2]

However, advocates for code reform argue that modern building technology has rendered the two-stair mandate obsolete for mid-rise structures. A building constructed in 2026 is fundamentally different from a 19th-century tenement. Modern single-stair proposals do not simply remove a staircase; they pair the single exit with a suite of advanced, active fire protection systems. These include mandatory automatic sprinkler systems, which extinguish most fires before they spread, and pressurized stairwells that actively blow air outward to prevent smoke from entering the escape route. Additionally, modern codes require non-combustible construction materials, such as concrete, steel, or mass timber, and strict compartmentation that seals each apartment behind heavy, fire-rated doors.[1]

The debate over safety was significantly clarified by a pivotal February 2025 report co-authored by the Pew Charitable Trusts and the Center for Building in North America. The researchers conducted a first-of-its-kind analysis of fire death rates in modern four-to-six-story buildings, comparing jurisdictions that allow single stairs with those that require two. The data revealed a striking conclusion: modern single-stairway buildings equipped with sprinklers do not present higher fire safety risks than dual-staircase construction. The report demonstrated that the active fire suppression systems and modern materials effectively neutralize the risks that the second staircase was originally designed to mitigate.[1]

The Pew report also highlighted real-world precedents within the United States. While most of the country banned single-stair mid-rises, cities like Seattle and New York City carved out exceptions decades ago. Seattle has permitted single-staircase buildings up to six stories since the 1970s, provided they meet stringent safety criteria. New York City has allowed similar structures under its own unique code. Decades of empirical data from these cities show no elevated rate of fire fatalities in these specific building types compared to the national average. This real-world evidence has been crucial in convincing skeptical lawmakers that the reform is grounded in proven safety records rather than theoretical models.[1]

Recognizing that the legislative momentum is outpacing traditional code-writing cycles, the fire safety community has begun to engage more directly with the reform movement. The National Fire Protection Association hosted an international symposium to bring together proponents and opponents of single-exit stairs. The goal was to move past political rhetoric and examine the technical data from Europe and Australia, where single-stair buildings are the norm. By fostering a dialogue between architects and fire marshals, the industry is working toward a consensus that balances the urgent need for housing supply with the non-negotiable demand for life safety, ensuring that new codes are written with rigorous technical oversight.[2]

Ultimately, the single-stair revolution represents a profound shift in how North America conceives of urban living. By aligning building codes with international standards, cities can unlock thousands of small, previously unbuildable parcels of land. This technical regulatory tweak has the power to replace sprawling, dark, hotel-style apartment blocks with bright, cross-ventilated, family-sized homes that fit seamlessly into existing neighborhoods. As more states adopt these evidence-based reforms, the missing middle of the housing market may finally be filled, proving that safety and affordability do not have to be mutually exclusive goals.[5]