Cross-laminated timber (CLT) panels have the potential to provide excellent fire resistance often comparable to typical massive assemblies of non-combustible construction. Due to the inherent nature of thick timber members to slowly char at a predictable rate, massive wood systems can maintain significant structural capacity for extended durations when exposed to fire.
In order to facilitate the acceptance of future code provisions for the design of CLT panels for fire resistance, a one-year research project was launched at FPInnovations in April 2010. The main objective of the project is to develop and validate a generic procedure to calculate the fire-resistance ratings of CLT wall and floor assemblies. A series of full-scale fire-resistance experiments is currently under way to allow a comparison between the fire resistance rating measured during a standard fire-resistance test and that calculated using the proposed procedure.
In light of the fact that the research project is just beginning, a simple but conservative design procedure is presented in this chapter, following the current state-of-the-art information from Europe and North America. The Canadian Standard for Engineering Design in Wood (CSA O86) can be used to calculate the fire-resistance rating of CLT panels along with the same methodology that is currently used for calculating the fire-resistance ratings of glued-laminated timber and “heavy” timber in the United States, New Zealand and Europe. This method is called the reduced (or effective) cross-section method and allows the use of the design values that can be found in CSA O86. It is recommended that a qualified fire protection engineer undertake or oversee the design of CLT assemblies for fire resistance. The fire protection engineer should work closely with the structural engineer so that the implications of fire exposure to the structural design are considered.