IRC 302.3 Two-Family Dwellings - Completely Revamped in the 2024 IRC - Summary of Changes

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2024 IRC Section R302.3 Summary and Changes from 2021: (Do you agree with this interpretation)​

• General Requirement for Separation:
  • 2024 IRC: Introduces specific sections (R302.3.1 through R302.3.6) to detail the separation requirements between dwelling units in two-family dwellings, emphasizing fire-resistance rated assemblies.
  • Change: The 2021 IRC generally required a 1-hour fire-resistance rating for separation, without breaking down into detailed subsections. The 2024 revision provides a more structured approach with clarity on separation aspects.
• Fire-Resistance Ratings and Testing:
  • 2024 IRC: Maintains the requirement for a 1-hour fire-resistance rating or a half-hour rating with an automatic sprinkler system. It specifies testing standards and an analytical method for determining these ratings.
  • Change: Clarifies and retains the basic requirements from 2021 but adds detail on testing and analysis methods for fire-resistance ratings.
• Continuity and Detailed Separation Requirements:
  • 2024 IRC: Emphasizes the continuity of the fire-resistance rating between dwelling units, specifying how horizontal and vertical assemblies should extend and be sealed against structural elements.
  • Change: This detailed approach to continuity and sealing requirements is an addition, offering clearer guidelines compared to the 2021 IRC's general requirement for assemblies to extend and be tight against exterior walls and other structures.
• Supporting Construction:
  • 2024 IRC: Expands the requirement that supporting construction for separating assemblies must have an equal or greater fire-resistance rating.
  • Change: While the 2021 IRC mentioned supporting construction for floor assemblies, the 2024 IRC explicitly extends this requirement to all separating assemblies.
• Vertically Stacked Dwelling Units:
  • 2024 IRC: Introduces requirements to limit smoke transfer and ensure interconnected smoke alarms for vertically stacked dwelling units without sprinkler systems.
  • Change: This is a new addition in the 2024 IRC, addressing specific concerns for vertically stacked units not covered in the 2021 IRC.
• Shared Accessory Rooms:
  • 2024 IRC: Provides detailed requirements for separating shared accessory rooms from dwelling units, including materials for separation, door protections, and handling of openings and penetrations.
  • Change: The detailed regulation of shared accessory rooms and specific protections for openings and penetrations are new in the 2024 IRC, enhancing safety measures beyond the general guidance in the 2021 IRC.
• Penetration and Opening Protections:
  • 2024 IRC: Details the protections required for ducts and other penetrations between shared accessory rooms and dwelling units, specifying materials and fire-protection ratings for doors.
  • Change: These detailed specifications for penetration and opening protections represent an expansion of the safety and separation guidelines not explicitly covered in the 2021 IRC.

Please note that the summary provided here offers a high-level overview of the changes and specifications detailed in the 2024 International Residential Code (IRC) Section R302.3, compared to the 2021 IRC. This summary is intended to highlight key changes and is not an official interpretation of the code. Codes can be complex and subject to interpretation by local authorities, so we strongly encourage reading the actual code sections in detail for yourself to fully understand the requirements and how they may apply to specific situations. For the most accurate and applicable guidance, always consult the full text of the code and consider seeking advice from a professional if needed.