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Expert Tips

Status of Building Code Allowances for Tall Mass Timber in the IBC

Jurisdictions that have adopted the tall mass timber code provisions in the 2021 and/or 2024 IBC International Building Code (IBC), either in whole or with local amendments.

Outdoor view mock-up of tall wood based building

Status as of February 2024

The 2021 International Building Code (IBC) has been published and is available for purchase through the International Code Council. This version of the code includes three new construction types—IV-A, IV-B and IV-C—that allow the use of mass timber or noncombustible materials in buildings up to 18, 12 and nine stories (respectively). Additionally, Group A changes to be incorporated in the 2024 IBC have been voted on and results ratified by ICC. One significant change relative to construction type IV-B is the allowance for exposure of mass timber ceilings and integral beams. The 2021 IBC permitted these areas to have 20% exposure while the 2024 IBC will permit 100% exposure. See the full code change language, which was approved as submitted, here.

The following jurisdictions have adopted the tall mass timber provisions in the 2021 and/or 2024 IBC, either whole or with local amendments.

For more information on the code changes, including design implications of the new construction types, see this WoodWorks paper and the ICC/American Wood Council document, Mass Timber Buildings and the IBC.

Several changes to the tall mass timber provisions within the 2021 IBC, which will be reflected in the 2024 IBC, have been approved during the ICC Group A cycle. These changes were voted on in late 2021 and ratified by ICC in 2022. Most notable, code change G147 will increase the allowable amount of exposed timber on ceiling and integral beam surfaces in Type IV-B from 20% to 100%. For additional information on this topic, see this WoodWorks expert tip.

For free project assistance related to the design of tall mass timber projects, or for general education related to the tall mass timber-related code changes, contact the WoodWorks Regional Director local to you. For information on the safety of tall mass timber buildings, development of the code changes and other related topics, see resources available from the American Wood Council and the Mass Timber Code Coalition.