Ricky McLain
Senior Technical Director - Tall Wood
WoodWorks – Wood Products Council, Cabot

Timber building design has reached an exciting confluence—that of the need for sustainable urban construction, which has never been higher, and the opportunity to use mass timber products, such as cross-laminated timber, for tall wood buildings. Because of their strength and dimensional stability, mass timber systems offer a safe, carbon-friendly alternative in applications where wood hasn’t traditionally been used.

In January 2019, having recognized the need for a uniform set of code provisions related to tall wood buildings, the International Code Council (ICC) announced changes to the 2021 International Building Code (IBC) allowing up to 18 stories of mass timber construction. Based on proposals from the ICC Tall Wood Building Ad Hoc Committee, the changes include three new construction types—Type IV-A, IV-B and IV-C—allowing the use of mass timber or non-combustible materials. These new types are based on the previous Heavy Timber construction type, but with additional fire-resistance ratings and levels of required non-combustible protection.

Due to a variety of factors, new tall wood code provisions and construction types now exist, as well as the technical research and testing that support their adoption. Design methods to address the new requirements include tall wood-specific high-rise and sprinkler requirements; methods of demonstrating fire-resistance ratings; fire design for penetrations, connections and abutting panels; allowances for exposed timber, exterior walls, concealed spaces, and more. The science and safety of tall mass timber buildings require strategies for designing these projects under the 2021 IBC.