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MAY 2019 csengineermag.com 31 To help visualize the building size associated with these tabular limits, the figure below shows representative buildings of equal area per floor with the maximum building sizes for a Business occupancy. As Business occupancies have the largest allowable areas and share the tallest height limits with other occupancies, these are the largest building sizes permitted by the new construction types, excluding minor additional area increases allowed by the frontage increase of IBC 506.3. Note that in the current IBC, the use of NFPA 13 sprinklers is mandatory for all high-rise buildings defined with an occupied floor more than 75 feet above the lowest level of fire department access. For existing construction types, the use of NFPA 13 sprinklers typically provides for a one-story and 20-foot increase in the allowable building height but a substantial increase in allowable area. However, the new construction types are highly conservative when allowable area is compared with common A, B and R occupancy groups where unlimited area is allowed for existing Type I buildings Conclusion The proposals from the ICC Tall Wood Building Ad Hoc Committee led to a comprehensive set of code changes developed using a rational performance-based approach to establish new size allowances for mass timber buildings in the IBC. The three new construction types have been crafted to support a variety of exposed and protected mass timber design systems which have been validated through fire testing. The American Wood Council's 2018 National Design Specification® (NDS®) for Wood Construction and Technical Report 10 have been pub- lished and together include updated provisions for structural fire-resistance calculations and protection of connections, as well as a summary of prior and recent fire testing providing substantiation for the design criteria. For more information, including a summary of the proposals, requirements for the new construction types, fire protection features, results of fire testing and other research, and an update to the CLT product standard, the complete paper can be found at http://bit.ly/2IF8kVB. WoodWorks–Wood Products Council provides free project support as well as education and resources related to the code-compliant design of commercial and multi-family wood buildings. For assistance with a project, visit www.woodworks.org/project-assistance or email help@woodworks.org. Representative Building Sizes, Business Occupancy Courtesy atelierjones, LLC 18 STORIES BUILDING HEIGHT 270 FT ALLOWABLE BUILDING AREA 972,000 SF AVERAGE AREA PER STORY 54,000 SF 12 STORIES BUILDING HEIGHT 180 FT ALLOWABLE BUILDING AREA 648,000 SF AVERAGE AREA PER STORY 54,000 SF 9 STORIES BUILDING HEIGHT 85 FT ALLOWABLE BUILDING AREA 405,000 SF AVERAGE AREA PER STORY 45,000 SF FRA-742_TALL-WOOD_Charts_March2019.indd 2

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