Overview of North American CLT Fire Testing and Code Adoption

Abstract

Cross laminated timber (CLT) is becoming more widely available in North America. However, it has not yet achieved widespread use in construction in the United States because provisions for CLT have only recently been added to model building codes. For example, CLT was recognized for the first time in the 2015 International Building Code (IBC), and the 2021 IBC will allow wood buildings made of CLT and other types of mass timber to be constructed up to 18 stories high. The changes to the 2021 IBC were implemented after several years of work from an ICC Ad-Hoc committee on tall wood buildings including fire testing supervised by the US Forest Service, Forest Products Laboratory. The fire tests involved five compartment fire test scenarios on a two-story building and specifically examined occupant egress and firefighter safety in corridors near the compartments. In addition to the fire tests performed by the Forest Products Laboratory, more large-scale fire tests were performed for the revision of the PRG-320 standard; the product standard for CLT in North America. These tests examined the heat resistance of adhesives used in CLT. This paper highlights the important changes to the IBC and the PRG-320 standard as well as summarizes the tests used to validate these changes.