A full-scale demonstration fire was conducted at National Research Council Canada (NRCC) to show that a 2-hr non-standard severe design fire in an apartment would have little or no effect on an adjacent elevator or stair shaft. The test was performed to support the approval of an alternative solution for a deemed-to-satisfy 2-hr noncombustible construction assembly, intended for the construction of a tall wood building in Quebec City (Canada). Throughout the duration of the fire no impact was observed in the CLT shaft: there was no evidence of temperature rise and no apparent smoke leakage. This suggests there was little to no effect of the design fire on the structure of the CLT shaft itself.