The Case for More Single Staircase Buildings in the United States
While recently covering the failed architecture and construction industries in the United States, I made a passing point about how single staircase buildings should be legal. This gave rise to several comments and discussions in a wide range of media. It is a subject that I have weighed in regularly for several years, but I had never seen so much dismay about it.
Simply put: buildings with only one staircase can be a good thing.
However, first I want to acknowledge the horrific tragedy of the Grenfell Tower in London. About its only similarity to European buildings is that the 24-story tower had a single stairwell. It was designed to compartmentalize the fires that did occur, but as the recent test laid bare it was poorly managed and poorly renovated, with an incredible number of wrong decisions leading up to the blaze.
Acknowledging this tragedy is important because I am not advocating that the construction be a free-for-all – in fact, far from it. Building regulations are necessary to establish minimum standards, safety and accessibility. Often they are data driven, but there are also cultural elements based on historical practices found in building regulations.
In the United States, building and energy regulations are written by a private entity rather than government agencies, as found in Europe, Canada, and most other countries. It should be noted that multi-family apartment buildings with one staircase are incredibly common in Europe and most do not have fire sprinklers either. This applies to existing, historic and new constructions. The tallest single-staircase building I’ve seen outside of the UK, by comparison, is only 10 stories tall.
Europe is full of pre-war single-staircase buildings such as Gaudi’s Casa Calvet in Barcelona, Spain – because this is how dense urban housing was built to accommodate the massive influx of migrant workers to cities, before the advent of the elevator and when people moved mostly on foot . In these urban centers, building plots were generally narrow and family-owned – and they were extended over time. Due to the narrowness there was mostly only room for a stairwell.
Most of the construction was not wood-frame like in the United States, but rather solid construction – generally brick or stone, and possibly concrete. Floors and roofs / inhabited attics were built with beams and wooden floors. Thus, many buildings were of the type where the vertical elements were relatively fire resistant, but the horizontal elements were not.
There was not professional firefighters until the 19th century. With little to no fire regulations, cities across Europe have experienced massive fires. Some, like Passau, in Germany, has experienced several fires that have destroyed the city on several occasions.
The details of construction and the appearance of concrete floors generally changed the equation on this subject, allowing compartmentalization slow down or contain fires. Mass Timber today can be designed to work the same way.
To this day, the single staircase configuration has persisted. But dual-load corridor buildings – buildings with units on either side of a central corridor – have been less common. I don’t know the exact reasons for this, but I think a lot of it is cultural. Double-loaded corridors prevent units from getting lights from multiple sides and does not allow cross ventilation, which is a growing problem on a warming planet. (Yes, even for multi-family passive house projects.)
Double-loaded hallways typically have dark hallways and result in less usable space per floor than a single-stair configuration, especially if your building code allows units to enter directly through the stairwell, such as this. This is the case in Germany, Austria and France. There are also structural tradeoffs with a dual load hallway, especially for a cellular or repetitive design building like a hotel, dorm or efficiency units. Buildings with only one staircase generally have more flexibility in their floor plan configurations.
Another problem with large buildings with double-loaded corridors is that there are more people using the same elevators, lobbies, and entrances. There are more people entering this type of building than in a single staircase configuration, due to limits on the number of units per floor. There are certainly social implications to assess, whether one is more personal or impersonal. Post-Covid, does it make sense to design buildings where many residents use the same public spaces or does it make sense to divide buildings into smaller modules?
So, what does this unique staircase configuration look like in Germany or Austria? Well, for starters, it should also be noted that there is usually no requirement for sprinklers. There are regulations on stairwells, fire walls and floors. There are limits on the number of units per floor for each staircase – four for Germany; eight for Austria. There are maximum travel distances to the stairwell (115 feet).
There are also limits to the height of the building: in Germany, the floor must be no more than 72 feet above the ground – usually seven or eight stories. Interestingly, 72 feet is the maximum wall height for most of the Berlin Altstadt, which was set to the maximum height of the rescue ladder, as well as the width of the street in the event of a collapse. There are tolerances to go a little higher with more stringent requirements on the exit and exit doors, as well as the availability of rescue devices that can reach this level. This is where it gets interesting.
Austrian architectural firm Querkraft Architekten designed an incredible 8-storey passivhaus multi-family building with a unique staircase configuration serving up to eight units per floor, in the heart of Vienna, Austria. Note the exterior concrete balconies (thermal break!). What is the function of the balconies? The function of the balconies is to access urban life, outside directly from your home. However, the most important thing is the second way out.
Yes, you read that right. As in the United States and Canada, German and Austrian building regulations require two means of escape. The difference is that, partly because of silos, their regulations allow second way out be the firefighters saving residents – even without sprinklers in the building. How do they do that? On the one hand, they have monstrous fire apparatus that can perform bucket rescues on tall buildings like this. rescue in Karlsruhe at 131 feet above sea level.
In Germany there is also very specific regulations on fire planning – where the buildings are located, separation between buildings or courtyards, the heights / widths to move or cross a building to a courtyard, as well as where the devices go to carry out these rescues. When I was working there a lot of my time was spent planning this stuff, studying schleppkurven (turning radii) and the arrangements of the devices. It may also be a function of smaller, more agile fire apparatus in Europe. It is also possible that their fire departments spend more time dealing with fires rather than medical emergencies, like in the United States.
Germany also allows multiple single staircase configurations to be used in the same building, such as in the charming walden48 baugruppe by scharabi + raupach architekten, a solid timber multi-family development which is effectively divided into 3 separate buildings, separated by fire walls. Likewise, the Dennewitz Einz baugruppe – a large development, 3 separate buildings, designed in collaboration by 3 separate architectural firms. These units receive light on multiple sides, cross ventilation, and a good variety in the mix of units. These extra measurements for the extra height that I mentioned is how a 10 story solid wood multi-family building with a single staircase, like the Skaio in Heilbronn, Germany, by the Berlin architectural firm Kaden + Lager, can be built.
Another personal favorite is this 9-unit, 7-storey social housing project by FRES architects in Paris – an astonishing project that would be infeasible if a second stairwell were required. As well as this multifamily building of 6 floors plus mezzanine and roof terrace of Lola Domènech and Lussi + Partner in the heart of Barcelona.
Mexico and Japan also have 10-story single-exit buildings. Despite this abundance of buildings with single staircase configurations and little to no active fire suppression, these buildings are quite safe due to compartmentalisation and building regulations. Many also have beautiful stairwells open to daylight for active use by residents.
Because FEMA Report, France, Germany, and Austria all have much lower fire death rates than the United States, where multiple stairs and active fire suppression are required for most multi-family buildings. Despite what we have been led to believe over the years, single-staircase multi-family buildings are legal even in some US jurisdictions. The International Building Code allows up to four floors, but with strict regulations including a maximum of four units per floor and requirements for sprinklers. Seattle allows up to six floors plus a mezzanine with a unique stair configuration.
Personally, I think it’s amazing that this kind of building is possible. Many are the smallest, fine town planning that make the great cities we talk about so often. They can be suitable for families, with a variety of unit types, and are both space and energy efficient. They are also accessible, as buildings on both continents require elevators on projects like this and many in Germany are barrier-free or adaptable.
Above all, they are legal. Maybe we should follow suit.