New report advocates for modernizing building code to allow multifamily “single-stair” construction
Bringing outdated codes in line with global standards would increase housing diversity and livability while using space more efficiently
October 10, 2024
Boston – A new report released today by Boston Indicators, in partnership with the Harvard Joint Center for Housing Studies and the Boston-based design firm Utile, calls for the modernization of Massachusetts building codes to allow for what is known as ‘single-stair’ construction for buildings of up to six stories and 24 units. The report, Legalizing Mid-Rise Single-Stair Housing in Massachusetts, suggests that modern fire suppression requirements, such as robust sprinkler systems, and recent data justify a new look at the regulations. A change in the code would result in feasible alternatives to the ubiquitous “five-over-one” residential buildings with two staircases that are currently favored by most developers. This report also looks at a wave of single-stair advocacy in the US and Canada, which has resulted in several cities, states, and provinces altering their regulations around these kinds of buildings. It seeks to bring the conversation to Massachusetts, which, despite its acute housing challenges, has struggled to produce needed housing.
“While the conventional wisdom suggests that two exit stairs on a long corridor is a non-negotiable necessity, the data suggests that single-stair buildings with four units per floor would not be any less safe,” said Sam Naylor, Associate at Utile and co-author of the report. “Not only do conventional two-stair residential buildings drive up construction costs, they limit design opportunities because they only fit on large sites. Since single-stair buildings have smaller footprints, they can be accommodated across a wider spectrum of lot sizes. As a result, they can be an important new tool for making a dent in our housing needs.”
The report explores the opportunity for mid-rise Point Access Blocks (PABs), a design familiar in many three-story or less developments, where units are built around a single central stairwell. Commonly seen in some of Boston’s most expensive older buildings in Back Bay and Beacon Hill, this construction style allows for better use of natural light, improved ventilation, and the opportunity for larger, family-sized units. Without long hallways, every unit in a PAB can have access to sunlight and fresh air, with windows on multiple sides.
Because they use space more efficiently on small footprints, single-stair designs also make building on smaller parcels of land easier, with designs that maximize density without sacrificing design quality. They also allow for a greater variety of unit sizes and configurations, including family-sized units that are currently scarce in Greater Boston’s housing market.
“In places like Boston, where small parcels are the most available opportunities for new housing development, single-stair designs unlock the potential for new units that can serve the widest variety of households,” said Chris Herbert, Managing Director at the Harvard Joint Center for Housing Studies. “It only makes sense to make them a larger part of our overall housing strategy.”
“We have rightly highlighted the role that MBTA Communities can play in creating more affordable housing, but changing zoning to expand land use for housing only solves part of the problem,” said Luc Schuster, Executive Director at Boston Indicators. “Coupling that work with untangling the building codes and standards that have been shown to limit mid-rise multifamily development can provide greater flexibility and reduce construction costs, which in turn can ease the burden for buyers and renters.”
A move toward PAB designs for “mid-rise” buildings up to six stories would bring Greater Boston in line with several industrialized countries, including many European nations and Japan, and put Boston on a par with New York City, Seattle, and Honolulu, among others. Data show that in the U.S., 99% of fire deaths occur in buildings without sprinklers, underscoring that sprinkler systems and modern fire-rated materials are more critical to safety than multiple exits.
Coupled with other code modernizations, such as reducing paths of travel, limiting floor plate size, and limiting numbers of units, the city could safely and efficiently create more beautiful units that safely meet the needs of families on parcels that are being underutilized at a time when Greater Boston is tens of thousands of units short of housing needed.