Split Switchback Housing

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Socially rich, straw-filled single-stair housing
Primary Projects + RUKA Design

Currently, most US housing over three stories requires two means of egress. This generates hotel-style housing, where units are entered from long, dark hallways. This model has many problems. Only allowing for windows on one wall leads to inefficiently laid-out units that are ill-suited to families, hard to ventilate naturally, and more. The excess circulation—an extra set of stairs and a long hall—necessitates large rectangular plots of land, which are increasingly rare and expensive in urban settings.

The US is a global outlier, with most peer countries allowing “single-stair” buildings of eight or more stories. Because the existing codes predate the invention of fire sprinklers (and more), many municipalities are reconsidering this regulation to spur the development of infill sites and reduce housing costs. Split Switchback Housing answers Denver’s call to imagine American single-stair housing.

The first floor caters to residents’ daily needs with spaces for chance meetings, play dates, package deliveries, bike parking, recycling, composting, & trash disposal.

The mid-level landings at the South protrude to signal entry and create covering at the side entry

Corrugated galvanized metal is low-cost, durable, fire-resistant, and materially-efficient cladding (shape + thin=rigidity).

Widespread Adoption

In surveying emerging single-stair legislation across the country, firefighters’ concerns have been the biggest barrier to adoption.

Before starting we worked to understand these concerns better, using them as the foundation to our approach. Building off of Seattle’s code, the design addresses these concerns in the following ways:

(Denver’s Capitol Hill, Station 8, has a truck with a 105’ rear-mount ladder. Denver has adequate hydrant capacity and quick fire department response times. The proposed building has fire sprinklers and properly fire-separated occupancies. All of these are essential factors for taller single-stair buildings.)

Short Travel Distances

The furthest unit is 12’ from the stair. (Also, the stair’s travel distance is equivalent to a typical switchback: 8’ across the landing.)

Fire-Rescue Balconies

Every unit has a balcony facing a right-of-way, allowing for easier rescue and refuge from smoke.

Smoke-Free Stair

The stair is covered, but open at the sides, preventing smoke build-up (and allowing more light & fresh air).

Increased Visibility

The alternating switchback increases visibility between floors (because they aren’t blocked by the level above).

The building’s design fosters connection and community, beginning with two street-facing social spaces—one at grade and one on the rooftop (left of image)

If you want to, it’s easy to chat with neighbors above or below you from your landing.

Ground Floor. From Left: Social Lawn, Covered Cafe Seating, Community Room, Bike Room, Utility Rooms, Stair & Elevator, One-Bed Units, Rear Balconies, & Retention Ponds

Second through Fifth Floor Plans. From Left: Street-Facing Balcony, Three-Bed Unit, Stair & Elevator, One-Bed Units, & Rear Balconies

Sixth Floor Plan. From Left: Street-Facing Balcony & Roof Deck, Shared Laundry & Communal Living Room, Stair & Elevator, One-Bed Units, & Rear Balconies

Unrolling a typical switchback stair opens up views & creates a portion of each landing where residents can pull over to chat, without increasing the travel distance!

In the case of a fire, the stair allows firefighters to see multiple levels more easily (normally views are obstructed by the stacking of the stairs).

The project consists of two living blocks organized around a central stair. Conceived as a prototypical solution, the blocks can grow or shrink to fit deeper or shallower sites, as long as their inner face abuts the stair.

Click through the gallery below to learn more about the project ︎︎︎

A bike room at the ground floor is a natural spot for residents to store and repair their bikes and strollers.

Recycled brick at the ground level & stair provides fire resistance & durability while recalling Denver’s brick legacy.

Every window in the project is operable, which allows residents to naturally condition their units during nice weather.

The balconies allow low winter light and screen out summer heat gain. (They also create a social interface with the neighborhood.)

Shared washers activate the rooftop communal space and save energy. Clothes-lines further conserve electricity.

A 500 gallon cistern on the roof captures runoff for plants (and communal compost converts kitchen scraps to fertile soil).

Sponsor

Buildner and ArchDaily

Location

1338 Emerson St / Denver, CO 80218

Timeline

2025

Awards

Denver Single-Stair Housing Challenge, Shortlisted

Stats

6-stories
16 units:
12 studios
4 three-beds
Lot Size: 5,678 sf (0.13 acres)
Dwellings per Acre: 122.7
Amenities: Covered Outdoor Cafe Seating, Community Room, Bike Room, Communal Living Room, Shared Laundry, Rooftop Deck, Social Stair

Services

Architectural Design
Zoning Analysis
Interior Design

Primary Projects