In 2015 the International Code Council formed an Ad Hoc Committee on Tall Wood Buildings to explore code changes to permit larger structures than currently allowed to be constructed of mass timber framing.
The committee recommended 14 code changes for approval:
- IBC Section 602.4 Type IV construction (G108-18)
- IBC Section 703.8 Tested noncombustible protection contribution (FS5-18)
- IBC Section 722.7 Calculated noncombustible protection contribution (FS81-18)
- IBC Section 703.9 Sealing of adjacent mass timber elements (FS6-18)
- IBC Section 718.2.1 Fireblocking materials (FS73-18)
- IBC Section 403.3.2 High rise sprinkler water supply (G28-18)
- IFC Section 701.6 Owner’s responsibility (F88-18)
- IFC Section 3314.7 Fire safety during construction (F266-18)
- IBC Table 504.3 (G75-18)
- IBC Table 504.4 (G80-18)
- IBC Table 506.2 (G84-18)
- IBC Section 3102.3 Special construction (G146-18)
- IBC Appendix D Fire Districts (G152-18)
- IBC Sections 508.4.4.1 and 509.4.1.1 Fire barriers at separated occupancies and incidental uses (G89-18)
A few of these in more detail:
- Creation of new Construction Types in Table 602.
- Type IV-A where the Mass Timber is protected with noncombustible material.
- Type IV-B where a limited amount of exposed mass timber elements are allowed.
- Type IV-C where mass timber is permitted to be unprotected.
Changes to the Allowable Building Heights in Table 504.
- Type IV-A buildings up to 270 ft sprinklered and 120 ft nonsprinklered
- Type IV-B buildings up to 180 ft sprinklered and 90 ft nonsprinklered
- Type IV-C buildings up to 85 ft sprinklered and 65 ft nonsprinklered.
- This would include A, B, E, F, M, S, U, I-4 and R Occupancies. More restrictive requirements would apply for other occupancies.
You can find more detail on the committee activities here: https://www.iccsafe.org/codes-tech-support/cs/icc-ad-hoc-committee-on-tall-wood-buildings/
There were Public Comment Hearings at the ICC Annual Conference in Richmond Oct. 21 to 29. This is being followed up by an Online Governmental Consensus Vote that will determine if these provisions move on to be included in the 2021 International Building Code.
Despite the back-up and documentation for these provisions that I’ve seen, this still makes me uncomfortable. As was noticeable from the project looming over the walkway immediately adjacent to the convention center at CSI’s convention in Long Beach, we already have construction teams stretching the limits of Type V construction and building wood framed structures to 75 feet on top of concrete podiums in urban areas. Do we need to go even taller and more dense with combustible members to support the timber industry? What will it take for us to learn the lessons from building fires of the past?