Given the housing affordability crisis and in light of the successful standards from New York and Seattle and the wide use of point access block design in other developed countries, it is time for Colorado and Lakewood to move quickly and allow increased flexibility for use of point access block design.
The potential for transformative change in our cities and towns, both in Colorado and beyond, is significant. With public awareness, industry momentum, and political will, policymakers have the opportunity to make a substantial impact.
Despite the size and scope of the problem, a small group of community-minded researchers at SAR+ Architects in Denver has spent the past several years looking for solutions.
Previous efforts lead the firm to successfully advocate in favor of updates to Denver’s zoning code to create more housing options by permitting accessory dwelling units (ADU) on single family lots throughout the city. Most recently, SAR+ examined Seattle in search of ideas and found something radical hiding in plain sight: the Point Access Block. Unlike traditional multifamily projects that are required by the building code to provide two stairs in buildings taller than three stories, the point access block uses just one.
With smaller footprints and lower land costs, Point Access Blocks promote affordability and attract a wider pool of developer participation by lowering the barrier to entry.
Potential Benefits of Point Access Block (PAB) Design
- Suitable for multifamily infill development on single lots or even half lots.
- Less land needed means lower land acquisition costs.
- One stairwell instead of two lowers construction cost.
- Financially feasible for smaller, local developers to participate.
- More windows per unit.
- Less space devoted to common hallways and stairwells.
- Much easier to include 2 and 3 bedroom floorplans.
- Allowed in Seattle since the 1970s up to 6 stories.
- Already the multifamily standard in most developed countries.
There is one chapter in the IBC that cities across the United States are ignoring in their sustainability approach, and that is Chapter 10.
Buried within Chapter 10 of the IBC, you find the double stair egress requirement – this code mandate has systematically pushed multi-family buildings in the US towards larger development that is inherently less sustainable and detrimental to city development. Single stair residential buildings, also known as Point Access Blocks, offer an alternative building typology that is ample with opportunity to reduce the carbon impact of housing and improve resident’s quality of life. With changes to the double stair egress requirement, states and local jurisdictions can expand their sustainable building development approach.
Typically, in a multi-family building in the US, we build double loaded corridor buildings, meaning the apartments or units are built on both sides of the corridor. This configuration creates long corridors embedded in the middle of the building decorated solely with unit doors. These corridor layouts feel stark, vast, and lack natural daylight or connection to the outdoors – creating an entry point to your home more reminiscent of a hotel.
Point Access Block buildings, minimize circulation space in corridors, bringing tenants physically closer together at their unit entries, and centralizes movement to one stair which facilitates connection between neighbors and encourages physical activity.
Egress requirements in America’s IBC are some of the strictest in the world, but there are a few jurisdictions even within the United States that are more accepting of small-lot, single-stair development. Seattle, New York City, Vermont, and the island of Oahu (housing two-thirds of Hawaii’s population) all allow single-stair buildings to be built up to four (in the case of Vermont) or six (in the case of the other jurisdictions) stories, taller than the IBC’s three-story limit. They achieve acceptable levels of safety by strictly limiting the size of buildings, as well as various combinations of construction material limitations and additional active fire protection features like sprinklers and pressurization systems to keep the single stair free of smoke in the unlikely event of a fire that isn’t suppressed by sprinklers.
In Colorado though, current building code requirements still limit the development of new housing to large lots. These rules pose a problem for infill development on small lots where development becomes infeasible. For example, in 2020, the City of Denver published the East Area Plan, a guide for how East Denver can evolve and grow. The East Area Plan identified challenges to growth, which includes “over-zoned” small lots — parcels of land where the full potential of the zoning code is unlikely to be realized due to the building code’s onerous egress requirements, combined with other factors like parking requirements.
Whether at the level of the national model code-writing body, or the state legislature, or even local efforts like Nashville’s and other cities, the single-stair movement is growing. It’s only a matter of time before more of America joins the rest of the world in allowing this basic building block of urbanism.
(Note: Most of the info in this post is condensed from the articles cited in the links and below.)
What About Fire Safety?
The argument against point access block design is that fire safety may be reduced if there is only one stairway as opposed to two stairways. Fire safety concerns are valid but may be magnified by fire disasters in the 1800s and even earlier.
For example, “In the early hours of Sunday, September 2, 1666, a fire broke out in a bakery on Pudding Lane. The fire burned for 4 days, and by the time it was finally extinguished, it had burned through four-fifths of London (LFB Museum, n.d.). The dominant use of wood as a building material contributed to the spread of the fire, with English diarist John Evelyn (1661) calling London a “wooden, northern, and inartificial congestion of Houses.”
However, consider that point access design should include limitations on the number of units per floor, the number of stories allowed and requirements for sprinklers, fire resistant materials and even positive-pressure stairwells. Fire safety and suppression technology today is obviously far advanced compared to the 1800s and earlier. Yet fire safety concerns today may still harken back to unrealistic historical examples.
NFPA is a nonprofit organization that sets standards for fire protection in the United States that are often adopted into code, and one of its first model codes, published in 1927, was called the Building Exits Code (Bukowski and Kuligowski, n.d.). Today, the NFPA 101 Life Safety Code (the modern successor to the Building Exits Code) and the NFPA 5000 Building Construction and Safety Code recommend allowing up to four stories of apartments around a single stairwell, subject to a few conditions that are similar to those found in Seattle’s code—for example, four units per floor at most, sprinklers throughout the building, and a 1-hour fire resistance rating for walls around the exit stair and corridors leading to it.12
If PABs were unsafe, then other countries and cities would surely have an excess of fire deaths compared to the United States. But the fact is we are much more unsafe!
The U.S. Fire Administration’s 2009 report highlighted lower average death rates in countries allowing Point Access Blocks taller than 20m (65′) compared to the U.S. Most U.S. codes mandate sprinklers for multifamily buildings over 2 stories, while many E.U. countries don’t require sprinklers for Point Access Blocks under 28m (92′). This discrepancy extends to other fire safety codes, with the U.S. having more stringent requirements like fire-rated corridors, unlike many E.U. nations.
“While fire safety is (and should be) paramount, the issue is that in many mid-rises, fatalities often happen when people are bunched in hallways looking for an exit. Anecdotally speaking, when a fire alarm went off a hotel I was staying at, it took several minutes just to get to the stairs due to crowding and confusion. PABs are simpler, and thus, I would argue safer.”
But these concerns are also raised with accessibility in other ways, for instance with ADA regulations. More elevators, after all, make it easier for those with physical limitations to get around quicker. But again, the beauty of the PAB is that access and egress is directly outside of the unit door meaning for those with movement disabilities, PABs bring you right to your door rather than forcing those individuals to take an elevator then continue for several dozen feet down a hallway.
The Double-Loaded Corridor Floor Plan
The requirement for a second exit led to a distinctive design in North America—the double-loaded corridor floor plan. Multifamily buildings in the United States and Canada generally center around a long, straight hallway bisecting the building along the narrower dimension, with many units arrayed on either side. In much of the world, this design is most characteristic of hotels or student dormitories (Eliason, 2023).
In most of North America, it has become the only realistic way to build apartments.
We need more options. Building primarily more luxury market-priced rental housing is not solving the affordability problem. Reducing project costs and expanding infill options may be a key to expanding affordability and point access block design enables that approach.
References:
Point Access Blocks: A Building Typology for a More Resilient Future
Point Access Blocks: Improving Colorado Housing
DENVER SINGLE-STAIR HOUSING CHALLENGE
