The International Residential Code (IRC) provides a comprehensive set of building, plumbing, mechanical, fuel gas, and electrical requirements for one- and two-family dwellings and townhouses up to three stories in height. Designed to promote safety, structural integrity, and code compliance, the IRC incorporates important updates that reflect modern construction practices and engineering standards.

Key revisions include updated seismic design maps that now reflect the most conservative Seismic Design Category (SDC) for all soil types, along with a new map that permits less conservative SDC classifications when Site Class A, B, or D conditions apply. Townhouse separation requirements have also been expanded to allow either two independent fire-resistance-rated walls or a single common wall assembly.