US Building Codes Restrict Spiral Staircases in Multi-Family and Common Areas

Building codes across the United States significantly limit the use of spiral staircases, particularly within multi-family dwellings and shared spaces, due to stringent safety and egress requirements. While not entirely prohibited, their application as a primary means of exit is severely curtailed, often leading to confusion among property owners and developers.According to a recent social media post by Gianmatteo Costanza, "Spiral staircases can only be part of an exit path inside individual dwelling units or tiny spaces (under 250 sq ft, up to 5 occupants). They’re not allowed in common areas, corridors, or larger shared spaces in multi-family buildings." This statement reflects the general consensus found in major building codes.The International Building Code (IBC) and International Residential Code (IRC), widely adopted across the U.S., outline specific conditions for spiral stairways. For instance, the IBC permits spiral stairways as a component in the means of egress only within individual dwelling units or from a space not exceeding 250 square feet and serving a maximum of five occupants. This restriction extends to common areas, corridors, and larger communal spaces, where conventional stairways are mandated for safety.These regulations are primarily driven by concerns over emergency egress and accessibility. Spiral staircases, by their nature, can be more challenging to navigate, especially for individuals with mobility issues or during a rapid evacuation. Codes specify minimum clear tread depths, riser heights, and headroom to ensure usability, but even with these, their use as sole egress is limited.Experts advise consulting local building inspectors before installing spiral staircases, as local jurisdictions may have additional requirements or interpretations. The focus remains on ensuring that all building occupants have safe and efficient exit routes, particularly in high-occupancy or multi-story structures.