The two-staircase requirement in the International Building Code makes small apartment buildings above 3 stories financially unbuildable across 97% of the US

The International Building Code (IBC), adopted by nearly every US jurisdiction, mandates that any residential building above three stories must contain two separate staircases for fire egress. This rule eliminates an entire category of housing — the 4-to-6-story "point access" apartment building with 6-12 units per floor arranged around a single stair and elevator core — that is the workhorse of housing production in Europe, Asia, and Latin America. The second staircase costs $190,000 to $380,000 per building in direct construction, but the real damage is spatial: it eats 15-20% of each floor plate. In a modeled comparison, a single-stair design fits 10 apartments per floor versus 9 in the two-stair version. Multiply that across 5 floors of a mid-rise and you lose 5 units per building. At scale, this means tens of thousands of missing apartments nationwide. A Pew Charitable Trusts study found that Massachusetts alone could add up to 130,000 units near transit stops if single-stair buildings were permitted. Meanwhile, a 2025 Pew safety analysis found that small single-stairway buildings have a strong safety record — the rule is not justified by fire outcome data. This problem persists because building codes are updated on a 3-year cycle by the International Code Council, a private body whose voting membership is dominated by building officials — not architects, developers, or housing advocates. Local jurisdictions then adopt the IBC wholesale, often without examining individual provisions. Fire departments lobby to retain the two-stair rule despite evidence that sprinklered single-stair buildings with enclosed corridors are as safe or safer. As of early 2026, only a handful of jurisdictions (Colorado, Austin, Seattle, Portland) have adopted single-stair reform, leaving 97% of the country locked into a rule that makes small-scale urban housing impossible to pencil out.