Early in design we determined our mass timber building would be 12 stories. That would classify us as a Type IV-B. The first hurdle we encountered was timber exposure limits.
In the 2021 IBC, Type IV-B construction is only allowed to expose 20% of the CLT in the building. That meant wrapping 80% of the beautiful wood with non-reusable, wasteful drywall. It defeated both purposes of aesthetics and carbon reduction, and the added costs would have made our project infeasible.
Fortunately the group who wrote the 2021 IBC tall wood codes had created a proposal to amend the 2024 IBC called G147-21. This proposed 100% allowable exposure in Type IV-B based on new CLT fire testing that was performed.
We joined them in Pittsburgh to testify before the International Code Council in support of this amendment. We had opposition from Ready-Mix Concrete and gypcrete lobbyists, who seem to be afraid of mass timber.
Fortunately our data was solid and we won on the ICC floor, and later this amendment was approved by code officials around the country and officially codified into the 2024 IBC.
So now (If your City has adopted this 2024 IBC provision) you can build 12 stories of mass timber and expose all of the wood! This was a huge milestone for us as our project would likely have died without it.
In September we testified before the ICC proposing changes to the International Bldg Codes that would loosen unnecessary restrictions on Mass Timber construction.
Today I learned our proposals passed and will be adopted into the 2024 IBC!
Huge win for Sustainable Development!