Regulatory framing: Changes to the International Building Code
The 2015 International Building Code (IBC), adopted by most states, was the first to recognize cross-laminated timber (CLT), specifically for use in Type IV buildings. Other mass-timber products are allowed in Type III and Type V buildings. All three of these building types cap residential construction at five stories and business construction at six stories.
The regulatory framework for mass timber is expanding upward, however, allowing for taller buildings to be built with CLT and other mass-timber products. In January 2019, the International Code Council approved key proposals to the 2021 IBC that allow for larger wood buildings:Type IV-A allows for a maximum of 18 stories (270 feet), with gypsum wallboard on all mass-timber elements Type IV-B allows for a maximum of 12 stories (180 feet) and a limited area of exposed mass-timber walls and ceilings Type IV-C allows for a maximum of nine s