This comprehensive publication provides a convenient reference for regulations in chapters 12 through 43 of the 2021 International Residential Code. The commentary series is presented in an easy-to-understand format. Every chapter begins with "General Comments" and "Purpose" sections followed by code and commentary to subsequent sections, tables and figures. This in-depth publication focuses on providing the full meaning and implications of the 2021 IRC. The commentaries are designed to suggest the most effective method of application, and the consequences of not adhering to the code.