[Credit: CNU Mid-Atlantic Single Stair Building Competition]
Single-stair is the default layout for buildings in most of the world outside of North America. Units in single-stair buildings are arranged around a central stairwell (and usually an elevator) serving all units, resulting in a slim building footprint that can fit onto small infill lots. European cities owe much of their famous charm, vitality, and walkability to their fundamental building block: single-stair buildings.
Due to the lack of a central hallway, units in point-access blocks (another term for this building type) are able to run the full depth of the building and often have windows on two or three sides. Slim floor-plates allow for the preservation of mid-block open space. Single-stair’s efficiency and flexibility contributes to dense, walkable, and fine-grained neighborhoods and cities.
Comparison of a Double-Loaded Corridor Building (left) and a Single-Stair/Point Access Block Building (right). The units on the right are much more varied, allowing for more family-sized units.
Despite their clear benefits, single-stair buildings are not prevalent in most North American cities due to building codes that restrict them to three stories. Buildings taller than three stories are usually required to have two stairwells linked by an interior corridor.
The double-egress rule was conceived of with fire safety in mind, but modern advances in fire safety and building materials have diminished the rule’s usefulness, turning it from a golden rule of building design to a suppressor of housing supply and urban vitality. Requiring two stairwells bloats a building’s footprint, decreases possibilities for unit layout and fenestration, makes it difficult to provide spacious, sunny, and well-ventilated units suitable for families, and decreases the ratio of usable square footage to circulation space. As a result of the two-stairwell requirement, most small infill lots are considered undevelopable and remain vacant – but this may soon change.
In the last few years, architects and housing policy wonks have caught on to the development potential and design possibilities foreclosed by this tiny code detail, sparking a lively movement for “single-stair reform” in North America that has resulted in around twenty state and local bills.
While cities like Seattle have allowed single-stair buildings since the 70’s, it was only in the last few months that Oregon adopted an optional building giving cities permission to allow single-stair buildings up to 4 stories. This competition aims to share the possibilities this reform opens up across Portland, and Oregon more broadly.
**secondegress.ca (Conrad Speckert)**