Changes to the Structural Requirements of the International Existing Building Code

by Jamie L. Davis, P.E., LEED AP

The 2020 Building Code of New York State is coming our way soon and will be based on the 2018 i-Codes, including the International Existing Building Code 2018 IEBC. There are some subtle but potentially significant changes that will affect how we retrofit existing buildings.

Summary of Changes:

Chapter 2: Definitions

A definition has been added for a Substantial Structural Alteration. This definition notes that a Substantial Structural Alteration occurs when the gravity load carrying elements that support 30 percent or more of the total floor and roof area have been altered.

The definition of Substantial Structural Damage has been expanded to define a limit of damage for elements carrying snow load. If the limit is exceeded, the elements must be reinforced.

Chapter 3: Provisions for All Compliance Methods

301.3 – The Exception that stated that “When considering the seismic force resisting system of an existing building…Alterations that complied with the laws in existence at the time the building was built were considered in compliance with the Code…unless undergoing more than a limited structural alteration” has been deleted. The revised wording of the Exception states that ‘Alterations complying with the laws in existence at the time the building was built are in compliance;’ however, it then notes that the Exclusion does NOT apply to the structural provisions for Alteration Levels 1 through 3.

This is a significant change. In accordance with the 2015 code, if we were considering the lateral system of a building undergoing an Alteration, the Exception allowed us to only evaluate how the Alteration affected the lateral system under wind loading. Seismic loads did not need to be evaluated unless the building was undergoing a substantial structural alteration. In accordance with the 2018 code, all buildings undergoing an Alteration will need to be evaluated to determine how the Alteration affects the lateral system under both wind and seismic loads.

303 – A section on Structural Design Loads and Evaluation and Design Procedures has been added. This section notes that where the usage of a space has not been changed by the Alteration, the structural elements are permitted to be designed for live loads that existed prior to the Alteration. However, if that live load is less than the current IBC live load for that same usage, the live load must be posted with placards.

This section also notes that if an Alteration or Addition causes snow drift on an adjacent building, the code official is authorized to enforce Section 7.12 of ASCE 7, which states that the existing roof shall be evaluated for increased snow loads caused by the Additions or Alterations, and Owners shall be advised when a higher roof is constructed within 20 feet from their building.

Chapter 4: Repairs

The provisions for Repairs have been pulled out of the Prescriptive and Work Area Chapters and are now in their own chapter.

405.2.1.1 – This section has been added and addresses elements damaged by snow and notes they should be reinforced for IBC snow loads.

Chapter 7: Alterations – Level 1

706.2 – The section noting structural requirements for reroofing has FINALLY been clarified to state that if the alteration increases dead, live, or SNOW loads (including snow drift) by more than 5 percent, it shall be altered to support current code-required loads.  This section formerly stated that the roof only needed to be evaluated if DEAD loads were increased by more than 5 percent. This clarifies the debate on reroofing projects when more insulation is added to an existing roof, thus reducing heat loss and potentially increasing snow loads.

Chapter 9: Alterations – Level 3

Section 906.7 – This section has been added and notes that buildings in Seismic Design Categories C or higher must anchor the top of masonry partition walls and nonstructural walls that are adjacent to egress paths to withstand reduced seismic forces.