The Ontario Building Code | Rooftop Enclosures
184.108.40.206. Rooftop Enclosures
(1) Rooftop enclosures provided for elevator machinery, stairways and service rooms, used for no purpose other than for service to the building, shall not be considered as a storey in calculating the building height.
9.10.5. Permitted Openings in Wall and Ceiling Assemblies