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Klaus Philipsen
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Is Housing Overregulated?
First, we make the building codes, then they shape our cities, which then shape us.
Occasionally, when the codes become too thick and the cost too high, we fight back, as in the quest to lower the cost for multi-family housing by allowing the cheaper wood construction we know from single family homes. Model codes now permit up to six floors in what is aptly called, "stick-built" fashion. This new construction type has quickly taken over coast to coast.
However, the housing shortage persists and code watchers have identified the next frontier: The dual exit stair requirement. Across the country building codes are being modified to allow six story buildings with a single exit stair instead of the maximal three stories allowed under the International Building Code (IBC).
If this sounds alarming to you, especially in the combination wood and single exit, you should read on. The matter is more complicated than one might think. In the century since the dual exit stair became the standard, a lot has happened in fire protection and safety. The extent to which fire codes have shaped urban design is usually underestimated: The two exit requirement and the "five plus one" height formula have homogenized our cities from sea to shining sea while the size of fire trucks has shaped our suburbs. Let's unpack the issues one by one, safety, fire protection and urban design.
Fire, Floors and Exits
Section 1006 of the International Building Code (IBC) demands two separate means of egress for every larger building over three floors and more than four dwelling units; commercial buildings with one exit are limited to only two floors. In addition, a host of additional codes such as the International Residential Codes IRC), the National Fire Protection and Prevention Association Life Safety Code (NFPA 101) put the fine points on the matter and provide some variation. (NFPA currently allows four floors for single exit buildings).
Fire has shaped cities throughout US history. Entire downtowns were wiped out by fire in several cities (Chicago, Baltimore and others) owed to the then common wood construction. Those catastrophic events resulted in more stringent requirements for materials and egress, including demanding two exits that are fire and smoke separated from the rest of the building, built from non combustible materials and lead directly to a public space. Both exit stairs must be accessible form each door leading into a protected egress-way. Thus, should one stair be blocked or smoke-filled, a second route is available within a maximum distance of 250 feet. Dead-end corridors are limited to 25 feet of length. Fire ravaged cities often prohibited combustible construction materials the central areas that hadbeen devastated. But today expanded downtowns have made those old restrictive boundaries obsolete while housing has taken over many previously commercial buildings.
Fire codes made a big leap when sprinklers became mandatory in almost all new buildings and open atriums or open stairs were only allowed with smoke evacuation .Flimsy, narrow and steep external fire escapes no longer count as a secondary exit. Wood and steel must be wrapped with fire-resistant materials. Sprinklers, in particular, had a dramatic effect; fire deaths in sprinklered buildings are almost unheard of. Proponents of the single exit point to the improved safety records and point to other countries that continued to build single exit buildings of considerable size with fewer fire deaths than we experience.
As a result, fire safety codes are rapidly crumbling under the onslaught. Politicians in State and local governments feeling the need to act began to create their own rules allowing taller single exit structures threatening the long-standing practice of science-based national model codes which are shaped by experts and subsequently adopted by local government. The Colorado Governor recently signed a bill allowing five story buildings with single exits. Baltimore City is currently considering a bill allowing six stories. This shift worries fire professionals.
Wood Construction
The relatively low cost of lumber compared to the the rising prices for steel and concrete drive the wood construction renaissance, further fueled by sustainability and climate concerns. In contrast to carbon spewing concrete and energy intensive steel, wood captures carbon; plus it is abundant and renewable. With the concrete "plinth" of retail, parking or amenities, a stud building can now have a total of six stories. Combine the two exit stair requirement with the height limit 5+1 and those long rectangular boxes that are 60' tall and sometimes span entire blocks are the result, almost by necessity.
The Center for Building was created to promote the change of building codes.
Its spokesperson is the Seattle based single exit building advocate and architect Michael Eliason summarizes his position this way:
The latest frontier is a wooden high-rise made from "mass timber", once again promoted because of carbon capture and sustainability. In this case, the IBC moved rather promptly: With mass timber for columns, beams and floors, 18 stories are now allowed. So far mass timber buildings are expensive and relatively rare, so we will ignore them for this story. (See my 2019 article about CLT)
Can One Exit be Safe?
Naturally, answers to the single exit question differ. Confusingly, the US have higher fire death rates than many countries in Europe, spite of our strict two exit requirement.
As someone who has practiced overseas and in the US, and has conducted a forensic apartment fire study and renovated countless old buildings, I would say that our fire death rate is caused by a combination of factors, including the prevailing wood construction, sloppy construction of older affordable three story walk-up apartment buildings and rowhomes without sprinklers, attics lacking proper firestopping, as well as social issues. Many fire deaths occur in abandoned buildings occupied by squatters or dysfunctional, disabled or missing smoke alarms.
In contrast, older buildings in Europe are usually constructed using masonry, concrete and sometimes heavy logs , i.e. lower fire-loads. Most European cities also experience less abandonment than we do. Five and six story apartment buildings in Paris or Berlin frequently have balconies or "French Doors" allowing rescue from the street via ladder while the typical US apartment has no outdoor space. Double-hung window with screens complicate rescue, especially when painted shut. In other words, it is easy to point to the beauty of European cities with their single exit buildings, but it is hard to see that their construction would offer cost savings. Finally, fire safety is not just driven by the way we build but also by how well fire departments are funded, how many hydrants are placed where, how much water pressure do they have how far away is the nearest fire house.
Fire professionals organized in the NFPA are cautious; in their Journal under the title "Single Stair, Many Questions" they diplomatically state:
The NFPA hosted an international symposium focused on the single exit stair issue in September 2024 at their Headquarters in Quincy, Massachusetts. Representatives from the United States, Canada, the United Kingdom, and Australia included proponents and opponents. A detailed report highlights the various viewpoints. In spite of the open minded symposium it appears unlikely that the model codes will be changed this year. New York and Seattle have long allowed taller single exit buildings if certain criteria are met, but they have excellent fire departments. Meanwhile, politicians who find the model code update process too slow continue to take the matter into their own hands by modifying the codes for their own jurisdiction.
Conclusion
What is the bottom line? With fire professionals themselves unsure how to respond the path forward will likely include some trade offs for eliminating the second egress requirement. Conditions could include short maximum distances to the stairway, maintaining limits on the the number of units per floor, pressurization of the exit stair and maybe a 2hr fire separation from adjacent apartments, even when sprinklered (currently 1 hr separation is enough), possibly applying the commercial sprinkler code instead of the residential code. The use of wood for structural members above four floors should be carefully reviewed for single exit buildings, unless there is a very rigorous inspection program in place that ensures that the required fire protection of structural members and the separation between units is not compromised by sloppy construction. Chases, ducts, pipes and electrical outlets all too often weaken the ULI tested assemblies and are easily overlooked by inspectors.
State and local governments will continue to set their own relaxed standards while the slower process of model code modification is taking on steam. This has happened before for sustainability requirements and the rehabilitation code, will be temporary and not prevent an update of the model code that will eventually unify things again.
Single exit buildings won't solve the housing crisis by offering large cost benefits. Still, new permissible building types will open up more infill opportunities help and enrich the impoverished urban design that the two exit building boxes have imposed on our cities.
Klaus Philipsen, FAIA
Related on this Blog:
First, we make the building codes, then they shape our cities, which then shape us.
Occasionally, when the codes become too thick and the cost too high, we fight back, as in the quest to lower the cost for multi-family housing by allowing the cheaper wood construction we know from single family homes. Model codes now permit up to six floors in what is aptly called, "stick-built" fashion. This new construction type has quickly taken over coast to coast.
[td]
[/td]
[td]
Stick-built five plus one building San Diego
(Photo Philipsen)
[/td](Photo Philipsen)
However, the housing shortage persists and code watchers have identified the next frontier: The dual exit stair requirement. Across the country building codes are being modified to allow six story buildings with a single exit stair instead of the maximal three stories allowed under the International Building Code (IBC).
If this sounds alarming to you, especially in the combination wood and single exit, you should read on. The matter is more complicated than one might think. In the century since the dual exit stair became the standard, a lot has happened in fire protection and safety. The extent to which fire codes have shaped urban design is usually underestimated: The two exit requirement and the "five plus one" height formula have homogenized our cities from sea to shining sea while the size of fire trucks has shaped our suburbs. Let's unpack the issues one by one, safety, fire protection and urban design.
Fire, Floors and Exits
Section 1006 of the International Building Code (IBC) demands two separate means of egress for every larger building over three floors and more than four dwelling units; commercial buildings with one exit are limited to only two floors. In addition, a host of additional codes such as the International Residential Codes IRC), the National Fire Protection and Prevention Association Life Safety Code (NFPA 101) put the fine points on the matter and provide some variation. (NFPA currently allows four floors for single exit buildings).
[td]
[/td]
[td]
The popular full block sized wrap multi family housing around
a parking garage
[/td]a parking garage
Fire has shaped cities throughout US history. Entire downtowns were wiped out by fire in several cities (Chicago, Baltimore and others) owed to the then common wood construction. Those catastrophic events resulted in more stringent requirements for materials and egress, including demanding two exits that are fire and smoke separated from the rest of the building, built from non combustible materials and lead directly to a public space. Both exit stairs must be accessible form each door leading into a protected egress-way. Thus, should one stair be blocked or smoke-filled, a second route is available within a maximum distance of 250 feet. Dead-end corridors are limited to 25 feet of length. Fire ravaged cities often prohibited combustible construction materials the central areas that hadbeen devastated. But today expanded downtowns have made those old restrictive boundaries obsolete while housing has taken over many previously commercial buildings.
[td]
[/td]
[td]
Small er, European style single exit buildings
[/td]
Fire codes made a big leap when sprinklers became mandatory in almost all new buildings and open atriums or open stairs were only allowed with smoke evacuation .Flimsy, narrow and steep external fire escapes no longer count as a secondary exit. Wood and steel must be wrapped with fire-resistant materials. Sprinklers, in particular, had a dramatic effect; fire deaths in sprinklered buildings are almost unheard of. Proponents of the single exit point to the improved safety records and point to other countries that continued to build single exit buildings of considerable size with fewer fire deaths than we experience.
As a result, fire safety codes are rapidly crumbling under the onslaught. Politicians in State and local governments feeling the need to act began to create their own rules allowing taller single exit structures threatening the long-standing practice of science-based national model codes which are shaped by experts and subsequently adopted by local government. The Colorado Governor recently signed a bill allowing five story buildings with single exits. Baltimore City is currently considering a bill allowing six stories. This shift worries fire professionals.
Wood Construction
The relatively low cost of lumber compared to the the rising prices for steel and concrete drive the wood construction renaissance, further fueled by sustainability and climate concerns. In contrast to carbon spewing concrete and energy intensive steel, wood captures carbon; plus it is abundant and renewable. With the concrete "plinth" of retail, parking or amenities, a stud building can now have a total of six stories. Combine the two exit stair requirement with the height limit 5+1 and those long rectangular boxes that are 60' tall and sometimes span entire blocks are the result, almost by necessity.
[td]
[/td]
[td]
Comparison of allowable building heights with a single
exit (international)
[/td]exit (international)
The Center for Building was created to promote the change of building codes.
Its spokesperson is the Seattle based single exit building advocate and architect Michael Eliason summarizes his position this way:
The latest frontier is a wooden high-rise made from "mass timber", once again promoted because of carbon capture and sustainability. In this case, the IBC moved rather promptly: With mass timber for columns, beams and floors, 18 stories are now allowed. So far mass timber buildings are expensive and relatively rare, so we will ignore them for this story. (See my 2019 article about CLT)
Can One Exit be Safe?
Naturally, answers to the single exit question differ. Confusingly, the US have higher fire death rates than many countries in Europe, spite of our strict two exit requirement.
[td]
[/td]
[td]
The US has six times as many fire deaths as Switzerland but less than
Finland in 2007. Since then US fire safety has much improved.
[/td]Finland in 2007. Since then US fire safety has much improved.
In contrast, older buildings in Europe are usually constructed using masonry, concrete and sometimes heavy logs , i.e. lower fire-loads. Most European cities also experience less abandonment than we do. Five and six story apartment buildings in Paris or Berlin frequently have balconies or "French Doors" allowing rescue from the street via ladder while the typical US apartment has no outdoor space. Double-hung window with screens complicate rescue, especially when painted shut. In other words, it is easy to point to the beauty of European cities with their single exit buildings, but it is hard to see that their construction would offer cost savings. Finally, fire safety is not just driven by the way we build but also by how well fire departments are funded, how many hydrants are placed where, how much water pressure do they have how far away is the nearest fire house.
Fire professionals organized in the NFPA are cautious; in their Journal under the title "Single Stair, Many Questions" they diplomatically state:
The NFPA hosted an international symposium focused on the single exit stair issue in September 2024 at their Headquarters in Quincy, Massachusetts. Representatives from the United States, Canada, the United Kingdom, and Australia included proponents and opponents. A detailed report highlights the various viewpoints. In spite of the open minded symposium it appears unlikely that the model codes will be changed this year. New York and Seattle have long allowed taller single exit buildings if certain criteria are met, but they have excellent fire departments. Meanwhile, politicians who find the model code update process too slow continue to take the matter into their own hands by modifying the codes for their own jurisdiction.
[td]
[/td]
[td]
Floorplan comparison dual stair building (left) and single stair (right)
[/td]Conclusion
What is the bottom line? With fire professionals themselves unsure how to respond the path forward will likely include some trade offs for eliminating the second egress requirement. Conditions could include short maximum distances to the stairway, maintaining limits on the the number of units per floor, pressurization of the exit stair and maybe a 2hr fire separation from adjacent apartments, even when sprinklered (currently 1 hr separation is enough), possibly applying the commercial sprinkler code instead of the residential code. The use of wood for structural members above four floors should be carefully reviewed for single exit buildings, unless there is a very rigorous inspection program in place that ensures that the required fire protection of structural members and the separation between units is not compromised by sloppy construction. Chases, ducts, pipes and electrical outlets all too often weaken the ULI tested assemblies and are easily overlooked by inspectors.
[td]
[/td]
[td]
NFPA graphic showing the "life safety eco system"
[/td]State and local governments will continue to set their own relaxed standards while the slower process of model code modification is taking on steam. This has happened before for sustainability requirements and the rehabilitation code, will be temporary and not prevent an update of the model code that will eventually unify things again.
Single exit buildings won't solve the housing crisis by offering large cost benefits. Still, new permissible building types will open up more infill opportunities help and enrich the impoverished urban design that the two exit building boxes have imposed on our cities.
Klaus Philipsen, FAIA
Related on this Blog: