While covering America’s broken architecture and construction industries recently, I made a passing remark on how single stair buildings should be legal. This resulted in several comments and discussions across a spectrum of media. It is a topic I weighed in on regularly for several years, but I had never seen this much consternation regarding it.

Simply put: Single stair buildings can be a good thing.

However, I first want to acknowledge the horrific tragedy of London’s Grenfell Tower. About its only similarity to European buildings is that the 24-story tower had a single stairwell. It was designed to compartmentalize fires that occurred, but as the recent trial has laid bare, it was poorly managed and badly renovated, with an incredible number of faulty decisions leading up to the fire.

Acknowledging this tragedy is important because I am not advocating that construction should be a free-for-all — in fact, far from it. Building regulations are necessary for establishing minimum standards, safety, and accessibility. Often they are data-driven, but there are also cultural elements based on historic 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 single stair multifamily buildings are incredibly common in Europe and most don’t have fire sprinklers either. That goes for both existing, historic, and new construction. The tallest single stair building I’ve seen outside of the United Kingdom, in comparison, is only 10 floors.

Europe is laden with pre-war single-stair buildings — such as Gaudi’s Casa Calvet in Barcelona, Spain — because this was how dense urban housing was built to accommodate the massive influx of workers migrating to cities, before the advent of the elevator and when people got around primarily by foot. In these urban centers, building parcels were generally narrow and family-owned – and they were expanded on over time. Due to the narrowness, there was largely only room for one stairwell.

Most of the construction wasn’t wood framed like in the United States, but rather solid construction — generally brick or stone, and eventually concrete. Floors and roofs/inhabited attics were built with wood beams and floors. Thus, many buildings were of the sort where vertical elements were relatively fire-resistant, but the horizontal elements were not.

There was no professional fire brigade until the 19th century. With little to no fire regulations, cities throughout Europe had massive fires. Some, like Passau, Germany, had multiple fire events that destroyed the city several times over.

Construction detailing and the onset of concrete floors generally changed the equation on this, allowing for compartmentalization to slow or contain fires. Mass Timber today can be designed to operate in a similar manner.

To this date, the single stair configuration has endured. But double-loaded corridor buildings — buildings with units on either side of a central hallway — have been less common. I don’t know the exact reasons for this, but I believe a large part is cultural. Double loaded corridors prevent units from getting lights from multiple sides, and they don’t allow cross ventilation, which is a growing issue on a warming planet. (Yes, even for multifamily passivhaus projects.)

Double loaded corridors generally 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 off the stairwell, as they do in Germany, Austria, and France. There are also structural tradeoffs with a double-loaded corridor, particularly for a building that is cellular or repetitive in design like a hotel, dormitory, or efficiency units. Single stair buildings generally have more flexibility in their floor plan configurations.

Another issue with large double-loaded corridor buildings is there are more people using the same elevators, halls, and entries. There are more people entering this sort of building than would in a single-stair configuration, due to limits on the number of units per floor. There are certainly social implications for this worth evaluating, whether one is more personal or impersonal. Post-pandemic, does it make sense to design buildings where many residents are using the same public