The current study aims at evaluating the integrity failure (i.e. passage of hot gases or flames through the assembly) of CLT assemblies connected together using four types of commonly used panel-to-panel joints when exposed to the standard CAN/ULC S101 “Standard Method of Fire Endurance Tests of Building Construction Materials” [1] fire resistance time-temperature curve. The four types of joints include: 1) half-lapped, 2) internal spline, 3) single surface spline and 4) double surface splines.