This comprehensive code comprises all building, plumbing, mechanical, fuel gas and electrical requirements for one- and two-family dwellings and townhouses up to three stories. The 2021 IRC® contains many important changes such as:

• Braced wall lines must be placed on a physical wall or placed between multiple walls.
• The rated separation for two-family dwellings is 1 hour whether or not a lot line exists between units.
• Emergency escape and rescue openings require a clear 36-inch-wide path to a public way.
• An engineered design is required for storm shelters.
• A habitable attic is limited to one-half the area of the story below and the dwelling requires sprinklers.
• Updated Wind Speed maps match IBC and ASCE 7 maps.
• Deck design now considers snow load, tributary area for footing and post height, and guard details.
• Specific requirements for deck guardrails were added.
• Component and cladding wind pressures in Table R301.2(2) are updated for new design wind speeds and hip or gable roof profiles.
• Minimum footing size tables are revised to more accurately reflect current practice.
• Cripple wall requirements apply only to exterior cripple walls.
• New appendices for cob construction and 3D printed construction are added.
• A 30 percent reduction of airflow is permitted for balanced ventilation systems.
• Commercial gas cooking appliances are prohibited.
• The head pressure for a water test of DWV systems increased to 10 feet.
• Air vacuum testing is now permitted for plastic piping DWV systems.
• Section P2904 for dwelling sprinklers is expanded to more closely align with NFPA 13D.
• An emergency service disconnect is required in a readily accessible outdoor location.
• A surge-protective device (SPD) is now required at the service panel.
• The number of receptacle outlets required for peninsular and island countertops in kitchens is determined by the area of the countertop surface.
• GFCI protection is now required for damp and wet locations not included in the other 10 areas requiring GFCI protection.