The regulatory cliff between residential and building codes
Alex Armlovich: This week I wish I were reading an analysis of the consequences of the regulatory cliff between America’s single-family “International Residential Code” (IRC)1 and our multifamily “International Building Code” (IBC). One hypothesized reason for the 20th century disappearance of “missing middle” multiplex buildings–duplexes, triplexes, quadplexes, etc–is that beyond the direct zoning bans on them on most land in most US cities after WWII, these buildings also trigger stricter IBC rules, raising costs enough to make multiplexes uncompetitive compared to attached rowhouses built under looser IRC rules2. Architects in the New Urbanism movement, predating the modern YIMBY movement, have long advocated for allowing multiplexes similar in overall size to a single family mansion to be able to use the IRC rules available to mansions, but face opposition from the legacy fire protection lobby, who argue the IRC isn’t safe enough.