The Ontario Building Code | Exceptions in Determining Building Height

3.2.1.1. Exceptions in Determining building Height

(1) A rooftop enclosure provided for elevator machinery, a stairway or aservice room used for no purpose other than for service to the building, shall not be considered as a storey in calculating the building height.

(2) Space under tiers of seats in a buildingof the arena type shall not be considered as adding to the building height provided the space is used only for dressing rooms, concession stands and similar purposes incidental to the major occupancy of the building.

(3) Except as required by Sentence (5), the space above a mezzanine need not be considered as a storey in calculating building height provided,

(a) the aggregate area of mezzanines that are not superimposed does not exceed 40% of the open area of the room in which they are located, and

(b) except as permitted in Sentence (8) and Sentence 3.3.2.11.(3) the space above the mezzanineis used as an open area without partitions or subdividing walls higher than 1 070 mm above the mezzaninefloor.

(4) Except as required by Sentence (5), the space above a mezzanine need not be considered as a storey in calculating the building height provided,

(a) the aggregate area of mezzanines that are not superimposed and do not meet the conditions of Sentence (3) does not exceed 10% of the floor area in which they are located, and

(b) the area of mezzaninein a suite does not exceed 10% of the area of that suite.

(5) Except as permitted by Sentences (6) and (7), each level of mezzanine that is partly or wholly superimposed above the first level of mezzanine shall be considered as a storey in calculating the building height.

(6) Platforms intended solely for periodic inspection and elevated catwalks need not be considered as floor assemblies or mezzaninesfor the purpose of determining building heightprovided,

(a) they are not used for storage,

(b) they are constructed with noncombustible materials unless the buildingis permitted to be of combustible construction, and

(c) where they are intended to be occupied, they have an occupant load of not more than four persons.

(7) Mezzanines, elevated walkways and platforms that are intended to be occupied in Group F, Division 2 or 3 major occupancies need not be considered as storeys in calculating building height provided,

(a) the building is of noncombustible construction, and

(b) the occupant load is not more than four persons.

(8) The space above a mezzanine conforming to Sentence (3) is permitted to include an enclosed space whose area does not exceed 10% of the open area of the room in which the mezzanineis located, provided the enclosed space does not obstruct visual communication between the open space above the mezzanine and the room in which it is located.

(9) A service space in which facilities are included to permit a person to enter and to undertake maintenance and other operations pertaining to building services from within the service space need not be considered a storey if it conforms to Articles 3.2.5.15. and 3.3.1.23. and Sentences 3.2.4.20.(12), 3.2.7.3.(2), 3.3.1.3.(7), 3.4.2.4.(3) and 3.4.4.4.(9).