IEBC's Latest Update: Risk Category Implications for Building Additions

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The International Existing Building Code (IEBC) includes a new section, [BS] 1101.3 "Risk Category Assignment," that addresses how to determine the risk category for additions to existing buildings, especially when these additions have different occupancies from the existing structures. This is a pivotal section as it ensures that any new additions adhere to safety and structural standards that are appropriate for their use and potential risk. Here’s an educational breakdown of this section and its implications:

Understanding Risk Categories:​

Risk categories are classifications used in the building codes to reflect the level of hazard a building or structure poses to its occupants in the event of a natural disaster or failure. These categories range from I to IV, with I being the lowest risk and IV the highest, typically assigned based on the nature of the occupancy and its importance to community resilience and safety.

The New IEBC Section - [BS] 1101.3:​

• Occupancy Differences: When an addition to an existing building has a different use or occupancy classification, the risk category for both the existing building and the new addition must be determined individually. This determination should follow the guidelines set in Section 1604.5.1 of the International Building Code (IBC).
• Higher Risk Category for Existing Building: If applying these guidelines results in a higher risk category for the existing building due to the addition, this scenario is treated as a "change of occupancy." Consequently, the project must comply with Chapter 10 of the IEBC, which covers changes of occupancy and ensures that the entire building meets the necessary requirements for its new, higher risk classification.
• Higher Risk Category for the Addition: Should the addition itself fall into a higher risk category than when considered separately, both the addition and any existing systems (such as mechanical, electrical, or plumbing) that serve the addition must meet the IBC requirements for new construction matching the higher risk category. This ensures that the new part of the building, along with its integrated systems, provides the level of safety and performance expected for its risk category.

Educational Insights:​

This section highlights the importance of carefully evaluating the impact of additions on the overall risk profile of buildings. The main takeaways for building professionals and stakeholders are:

• Safety and Compliance: Ensuring that additions do not inadvertently compromise the safety of the existing structure or fail to meet the expected standards for their occupancy type.
• Consideration for Changes: Understanding that an addition can change the risk category of an existing building, potentially requiring significant upgrades to meet new safety standards.
• Holistic Approach to Building Safety: Recognizing that additions are not isolated projects but integrally affect and are affected by the existing structures’ safety and code compliance.

By introducing this section, the IEBC aims to promote a more nuanced and safety-oriented approach to building additions, ensuring they are not only functional but also adhere to the highest standards of occupant safety and building integrity. This move reflects an evolving understanding of how buildings interact with their extensions and modifications, emphasizing the need for a comprehensive review to maintain and enhance building safety in the face of changing uses and occupancies.