POINT ACCESS BLOCKS

AIA Philadelphia Housing Committee & AIA Philadelphia Advocacy Committee 

Aaron Bell, AIA 

The Housing Crisis and the Status Quo 

Housing costs continue to rise significantly faster than incomes, intensifying pressure on households already strained by recent inflation. Meanwhile, new construction has slowed to its lowest level since 2012, widening the supply-demand gap and further accelerating prices.1 In this economic climate, the charge for architects is to contribute workable solutions in the domain that directly shapes daily life: how we design buildings. 

Despite varied opinions on the housing crisis, a broad consensus is forming around the need for both more housing and more diverse formats. Yet the multifamily market in the United States remains dominated by a single model: the podium “five-over-one” with a double-loaded corridor. Originating as a cost-optimized pairing of Type V construction over a Type I podium, this typology maximizes allowable area while staying below the 75-foot high-rise threshold that would trigger more expensive systems. Its predictability also aligns well with conventional financing, reinforcing its status as the default. 

Diagram of a typical podium building.  

Image courtesy of The Harvard Joint Center for Housing Studies 

The podium model presents distinct challenges: the requirement for large floor plates and complex land assembly limits participation to well-capitalized developers and can delay housing delivery. Furthermore, it can be argued that these developments disrupt the urban fabric in rowhouse-scale cities like Philadelphia. By substituting traditional verticality with monolithic horizontal massing, these designs may be perceived as out-of-scale, potentially intensifying community opposition. 

This prompts a fundamental question: can multifamily housing be delivered in a form that is more contextually compatible, more scalable on typical urban parcels, and more feasible for a broader range of developers? Increasingly, the answer points toward “missing middle” strategies, particularly the Point Access Block (PAB), or single-stair building, now gaining national attention as a viable alternative. 

The Point Access Block 

Across Europe and East Asia, the Point Access Block is the prevailing multifamily typology, not the double-loaded corridor podium model familiar in the U.S. A PAB organizes a compact core, generally one stair and an elevator, around roughly four units per floor.  

Diagram of a 3 story apartment, point access block, and a five-over-one 

Image courtesy of Pew Research Center and The Center for Building 

These blocks can operate singly or in clusters. By largely eliminating corridors, they convert a greater share of the floor plate into dwelling space. The unit plans can vary widely in size and configuration, avoiding the corridor-driven bias toward one-bedroom units. Every residence gains at least two exterior exposures, enhancing daylight, enabling cross-ventilation, and reducing energy demand. 

Diagram of comparing podium building units to units in a point loaded building.  

Image courtesy of The Harvard Joint Center for Housing Studies 

Seattle first adapted single-stair buildings in 1977 as a tool for fine-grain urban infill. In developed urban cores, infill development can be challenged by small lot sizes or irregular lots, and PABs offer an alternative approach to building on 1 or 2 lots rather than a lengthy assembly process for building podium buildings.  

Diagrams of a typical PAB vs Podium Building  

Image courtesy of Pew Research Center and The Center for Building 

The Seattle Building Code limits buildings to six stories, four units per level, and floor plates of approximately 4,000 square feet, while imposing strict requirements for sprinklers, construction ratings, and egress distances. Although international examples often employ noncombustible construction and reach greater heights, the American versions are compact, efficient, employ active life-safety systems, and inherently have small-footprints averaging 2,000sf – 2,500sf. 

Image courtesy SAR+ Architects commissioned for Center for Building 

Safety 

The Point Access Block should be understood as a comprehensive life-safety system rather than a simple reduction from two stairs to one. In practice, PABs extend a very small floor plate vertically while adding compensatory protections. NFPA 101 already permits single-stair residential buildings up to four stories, and European models routinely exceed ten stories under different regulatory regimes. In Seattle and similar jurisdictions, fully sprinklered construction, controlled egress distances, and compartmentalization yield exit times of under one minute, often faster than fire department arrival. When properly executed, PABs represent a controlled, fully engineered approach to multifamily safety rather than a relaxation of established norms. 

International benchmarks for code restricted multi-family building heights. 

Image courtesy of The Harvard Joint Center for Housing Studies 

Cost and Affordability 

Research from the Harvard Joint Center for Housing Studies shows that PABs are roughly ten percent more efficient than comparable two-stair buildings, enabling more of the construction cost to be recovered through rentable area. 2 Eliminating a second stair and corridor produces additional savings of a similar scale. Their small floor plates allow development on one or two standard urban parcels, reducing acquisition cost, minimizing entitlement risk, and enabling participation by smaller, incremental developers. National data suggests that multifamily buildings around 16 units tend to command lower rents than large podium projects, strengthening their role as a market-driven affordability tool.  

Legislation 

Policy interest in PABs has accelerated in recent years. Colorado has authorized local jurisdictions to permit single-stair multifamily buildings, and California is considering statewide adoption. Minnesota, Tennessee, Texas, and others are studying the typology as a mechanism for gentle density within established neighborhoods.  

In Pennsylvania, the AIA Philadelphia Advocacy Committee has been examining PABs throughout 2025 in consultation with national experts and peer chapters. In 2026, AIA Philadelphia will continue to explore how PABs could be integrated into Philadelphia’s rowhouse fabric, accompanied by policy discussions with municipal and state leaders focused on life safety and code modernization. 

Reference 

1. Vincent Reina et al., Current Housing Needs in Philadelphia (Housing Initiative at Penn, May 2025), https://www.housinginitiative.org/uploads/1/3/2/9/132946414/hip_philadelphia_housing_needs_may2025.pdf. 

2. Elizabeth Christoforetti, Tim Love, and Luc Schuster, Single-Stair Housing in the Boston Region: Exploring the Planning, Design, and Financial Implications of Building Code Reform (Cambridge, MA: Joint Center for Housing Studies of Harvard University, October 2024), https://www.jchs.harvard.edu/sites/default/files/research/files/harvard_jchs_utile_boston_indicators_single-stair_housing_october_10_2024.pdf. 

3. Sean Jursnick and Peter LiFari, "The Single-Stair Solution: A Path to More Affordable, Diverse, and Sustainable Housing," Mercatus Policy Brief, Mercatus Center at George Mason University, June 6, 2024, https://www.mercatus.org/research/policy-briefs/single-stair-solution-path-more-affordable-diverse-and-sustainable-housing. 

4. Seva Rodnyansky et al., Small Single-Stairway Apartment Buildings Have Strong Safety Record (Philadelphia: The Pew Charitable Trusts, February 2025), https://www.pew.org/en/research-and-analysis/reports/2025/02/small-single-stairway-apartment-buildings-have-strong-safety-record.