Tall Wood Corner with Ricky McLain | April 2022
Apr 25, 2022 Ricky McLain
Although America wasn’t the first country to realize tall mass timber structures, the suggestion that it is new to these types of projects is fast becoming out of date.
U.S. interest in tall timber buildings, i.e., buildings that exceed height and area limits for wood construction prescribed in the 2018 and previous versions of the International Building Code (IBC), has steadily increased over the past several years. With the introduction of three new construction types in the 2021 IBC—Types IV-A, IV-B and IV-C, which allow up to 18, 12 and nine stories of mass timber construction respectively—these projects are also getting built. Currently, six mass timber buildings that exceed the 2018 prescriptive height limits are complete or under construction, and more than 140 are in design. In 2021 alone, tall projects such as INTRO in Cleveland, Ascent in Milwaukee, 11 E Lenox in Boston, 80M in Washington DC, and Apex Plaza in Charlottesville, VA either started or completed the mass timber portion of construction. At the time of this newsletter, several others are set to break ground.
As more design teams look to leverage the new tall wood opportunities in the 2021 IBC, a fundamental understanding of how to design these structures is necessary. Aspects unique to the new construction types include the ability to achieve fire-resistance ratings of mass timber elements through a combination of timber charring and noncombustible protection, special inspection requirements for components such as connections and anchorage systems, and limits on the amount of mass timber ceilings that can be exposed as a function of floor or fire areas.
WoodWorks recently updated its publication, Tall Wood Buildings in the 2021 IBC – Up to 18 Stories of Mass Timber. This document provides information for those looking to gain a more comprehensive understanding of the new construction types as well as the work of the International Code Council’s Ad Hoc Committee on Tall Wood Buildings in developing 17 tall mass timber-related code changes which led to the new code allowances. Included in the document is a summary of allowable building sizes, required fire-resistance ratings, amounts of permissible timber exposure, an overview of testing and research which facilitated the approval of the changes, and much more.
Read more about Tall Mass Timber.