The 2021 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. This edition introduces numerous updates designed to enhance safety, structural performance, energy efficiency, and construction practices.

Key revisions include updated requirements for braced wall lines, which must now be located on a physical wall or between multiple walls. The required fire-resistance-rated separation for two-family dwellings has been standardized to one hour, regardless of whether a lot line exists between units. Emergency escape and rescue openings must provide a clear 36-inch-wide path to a public way, and storm shelters now require engineered design.