Our previous post in November 2021, “Mass Timber – Exposed Wood in Type IV-B Construction”, provided insight into the allowances for exposed mass timber elements, specifically with Type IV-B construction, based on the 2021 IBC.
The proposal G147-21 has been approved as submitted for changes to Section 602.4.2.2.2 to be included in the 2024 IBC, expanding the allowable percentage of exposed mass timber elements in dwelling units or fire areas of Type IV-B buildings. The approved provisions are as follows:
- Ceilings are permitted to expose an area less than or equal to 100% of the floor area.
- Walls and attached columns are permitted to expose an area less than or equal to 40% of the floor area.
- A mix of both exposed walls and ceilings are permitted, using a mixed unprotected area equation, provided in Section 602.4.2.2.3.
This code change follows the recommendations from the ICC Tall Wood Building Ad-Hoc Committee, based on tests from the Research Institute of Sweden with fully exposed mass timber ceilings demonstrating satisfactory results with respect to performance objectives set for these building materials.
It should be noted that the 2024 IBC has not been finalized, and the base code will not be adopted for years; however, the approval of this code change provides opportunities for potential variances to allow for more exposed mass timber elements in Type IV-B buildings. For additional information or request for assistance on your project, please contact us at info@crcfire.com.