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

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.

• Alabama – adoption of the 2021 IBC
• Alaska – adoption of the 2021 IBC
• Arkansas – adoption of the 2021 IBC
• California – adoption of the 2021 IBC as part of the 2022 California Building Code
• City of Denver, Colorado – adoption of the 2022 Denver Building & Fire Code which incorporates the 2024 IBC allowances for tall mass timber
• City of Nashville, TN – adoption of the tall mass timber provisions from the 2021 IBC as an amendment to the Nashville Metropolitan Code
• Colorado – adoption of the 2021 IBC
• Connecticut – adoption of the 2021 IBC
• Georgia – Appendix P to the 2018 IBC
• Idaho – Amendments to the Idaho Building Code
• Illinois – adoption of the 2021 IBC
• Louisiana – adoption of the 2021 IBC
• Maine – Emergency Rule 3, amendments to the Maine Uniform Building and Energy Code (Section 5, item 25)
• Maryland – adoption of the 2021 IBC
• Memphis and Shelby Counties, TN – Adoption of the 2021 IBC
• Montana – adoption of the 2021 IBC
• New Jersey – adoption of the 2021 IBC
• New Mexico – adoption of the 2021 IBC
• North Dakota – adoption of the 2021 IBC
• Ohio – Adoption of the 2021 IBC
• Oregon – 2022 Oregon Structural Specialty Code
• South Carolina – adoption of the 2021 IBC
• South Dakota – adoption of the 2021 IBC
• Utah – adoption of the 2021 IBC
• Virginia – Adoption of the 2021 IBC
• Washington – Amendments to the 2021 IBC including some of the 2024 IBC allowances for tall mass timber
• Wyoming – adoption of the 2021 IBC

• Texas Jurisdictions:
  • City of Abilene – adoption of the 2021 IBC
  • City of Allen – adoption of the 2021 IBC
  • City of Arlington – Adoption of the 2021 IBC
  • City of Austin – adoption of the 2021 IBC
  • City of Bryan – adoption of the 2021 IBC
  • City of Carrollton – adoption of the 2021 IBC
  • City of Dallas – Ordinance 32198 which incorporates some 2021 and 2024 IBC allowances for tall mass timber
  • City of Fort Worth – adoption of the 2021 IBC
  • City of Frisco – adoption of the 2021 IBC
  • City of Grand Prairie – adoption of the 2021 IBC
  • City of Houston – Adoption of the 2021 IBC
  • City of Irving  – Adoption of the 2021 IBC
  • City of McKinney – Adoption of the 2021 IBC
  • City of Plano – adoption of the 2021 IBC
  • City of Richardson – Adoption of the 2021 IBC
  • City of San Antonio – adoption of the 2021 IBC
  • City of San Marcos – Adoption of the 2021 IBC

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.