Building size and construction relative to occupancy (Fire Protection)

Last updated October 22, 2026

Values this chapter turns on

perimeter within 15 m of streets to face 2 streets: 50%; perimeter within 15 m of streets to face 2 streets
max basement compartment if not sprinklered: 600 m²; max basement compartment if not sprinklered
crawl space height that makes it a basement: 1.8 m; crawl space height that makes it a basement
mezzanine share of a room not counted as a storey: 40%; mezzanine share of a room not counted as a storey

Subsection 3.2.2. decides how a building must be built for its occupancy, height and area: combustible or noncombustible, sprinklered or not, and what ratings the floors, roofs, mezzanines and supports need. It is also where most Part 3 sprinkler requirements come from. To use it you first need the right building height, building area and number of streets faced, then you pick the construction article.

Building height, area and multiple major occupancies

Building height counts storeys from the first storey to the roof (OBC Div. A 1.4.1.2.). Not counted (OBC Div. B 3.2.1.1.):

a rooftop enclosure used only for elevator machinery, a stair or a service room;
space under arena seating used for dressing rooms and concessions;
the space above mezzanines totalling not more than 40% of the room's open area, kept open above (partitions not over 1,070 mm), or not more than 10% of the floor area when not open;
inspection platforms and catwalks not used for storage.

Each superimposed level of mezzanine above the first counts as a storey.

The floor over a basement is a fire separation rated to the construction article but at least 45 min (3.2.1.4.). In a building not required to be sprinklered by 3.2.2.18., each basement is either sprinklered or divided into 600 m² fire compartments (3.2.1.5.). A basement storage garage can be treated as a separate building if the floor above and exposed basement walls are 2 h noncombustible fire separations (3.2.1.2.).

Multiple major occupancies. The height and area of the entire building are always used (3.2.2.5.). Where occupancies sit side by side, the most restrictive requirements apply to the whole building (3.2.2.6.). Where one occupancy is entirely above another, each portion follows the article for its own occupancy as if the whole building were that occupancy, and the floor between them is rated for the lower occupancy (3.2.2.7.). Occupancies totalling not more than 10% of a storey can be ignored for 3.2.2., unless F1 or F2 (3.2.2.8.).

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Streets, crawl spaces and roof occupancies

Every building must face a street, and an access route meeting 3.2.5. counts as a street (OBC Div. B 3.2.2.10.). The number of streets faced depends on how much of the perimeter is within 15 m of a street:

Perimeter within 15 m of streets	Streets faced
less than 50% (the building still faces its street)	1
at least 50%	2
at least 75%	3

Buildings under 3.2.2.51. and 3.2.2.60. have their own threshold for one street: at least 25% of the perimeter within 15 m of a street, or at least 10% where the exterior cladding meets Sentence 3.1.4.8.(2) (3.2.2.10.(3)).

Tunnels and enclosed bridges are never streets. A street itself must be at least 9 m wide and dedicated for public use.

A crawl space counts as a basement if it is over 1.8 m high, used for any occupancy, carries flue pipes, or is a plenum in combustible construction (3.2.2.9.). Otherwise the floor over it need not be rated. A roof that supports an occupancy (a roof terrace) is built to the article's rules for floor assemblies (3.2.2.13.).

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Sprinkler triggers and impeded egress zones

OBC Div. B 3.2.2.18. is the master list: a building governed by any article listed in Sentence (1) must be sprinklered throughout (almost every article with "Sprinklered" in its title is listed; check the list, because 3.2.2.64. carries that word in its title but is not listed), with the system meeting 3.2.4.7. to 3.2.4.9. (alarm connection and supervision) and 3.2.5.12. (design standard). Sentence (2) adds a rule that catches candidates: if any storey must be sprinklered, every storey below it must be sprinklered too.

Other triggers in this area:

Gymnasiums, pools, arenas and rinks may drop the roof and equipment-mezzanine rating in 3.2.2.25., 3.2.2.30. and 3.2.2.32. if the roof carries only normal loads and no part is less than 6 m above the floor or balcony (3.2.2.17.).
A building with an impeded egress zone escapes the B1 articles if it is sprinklered, 1 storey, has no contained use area, sleeping, F1 or mercantile occupancy, the zone stays within one fire compartment, and its occupant load is not more than 100 (3.2.2.19.).

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Construction articles by Group

Each article in 3.2.2.20. to 3.2.2.93. has the same structure: conditions (height, area, sprinklers), then construction type, then ratings for floors, mezzanines, roofs and supports. Its title tells you most of it. Some values to practise:

Article	Limits	Construction and floor rating
3.2.2.25. A2	up to 2 storeys, table area (1 storey 1,600 m² facing 1 street)	combustible permitted; 45 min if combustible
3.2.2.54. C	up to 3 storeys, 3 storeys 600 m² facing 1 street	combustible; 45 min floors
3.2.2.55. C sprinklered	3 storeys up to 1,800 m²	combustible; 45 min floors
3.2.2.62. D	up to 3 storeys, 2 storeys 2,400 / 3,000 / 3,600 m²	combustible; 45 min if combustible
3.2.2.66. E	any height and area	noncombustible, sprinklered, 2 h floors
3.2.2.70. E	up to 2 storeys, 2 storeys 600 m² facing 1 street	combustible; 45 min floors
3.2.2.75. F1	1 storey, 800 m²	combustible permitted

Common traps:

Using the area of one storey of a portion rather than the building area of the entire building.
Forgetting that choosing an article listed in 3.2.2.18.(1) makes sprinklers mandatory throughout the building.
Reading the wrong row (storeys) or column (streets) in an area table.

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Chapter review

Chapter at a glance

One line per section: the idea to carry into the exam. Then the answers that most often catch candidates out.

Chapter at a glance: the key idea in each section
Section	Key idea
Building height, area and multiple major occupancies	Building height counts storeys from the first storey to the roof.
Streets, crawl spaces and roof occupancies	Every building must face a street, and an access route meeting 3.2.5. counts as a street.
Construction articles by Group	Each article in 3.2.2.20. to 3.2.2.93. has the same structure: conditions (height, area, sprinklers), then construction type, then ratings for floors, mezzanines, roofs and…

Building height, area and multiple major occupancies
Building height counts storeys from the first storey to the roof.
Streets, crawl spaces and roof occupancies
Every building must face a street, and an access route meeting 3.2.5. counts as a street.
Construction articles by Group
Each article in 3.2.2.20. to 3.2.2.93. has the same structure: conditions (height, area, sprinklers), then construction type, then ratings for floors, mezzanines, roofs and…

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Questions on Building size and construction relative to occupancy, in the exam format, every answer explained and cited to its article. Sign in to start; a free account gets the free questions.

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Code cited in this chapter

Based on the official 2024 Building Code Compendium on ontario.ca.

OBC Div. A 1.4.1.2.(1) Building height (in storeys)
Building height (in storeys) means the number of storeys contained between the roof and the floor of the first storey.
Open OBC Div. A 1.4.1.2.(1) in the code viewer
OBC Div. B 3.2.1.1. Exceptions in Determining Building Height
(1)A rooftop enclosure provided for elevator machinery, a stairway or a service 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 building of 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 (See Note A-3.2.1.1.(3)(a))
(b)except as permitted in Sentences (7) and 3.3.2.13.(3) the space above the mezzanine is used as an open area without partitions or subdividing walls higher than 1,070 mm above the mezzanine floor.
(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 a mezzanine in a suite does not exceed 10% of the area of that suite.
(5)Except as permitted by Sentence (6), 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 maintenance catwalks need not be considered as floor assemblies or mezzanines for the purpose of calculating building height, provided
(a)they are not used for storage, and
(b)they are constructed with noncombustible materials unless the building is permitted to be of combustible construction.
(7)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 mezzanine is 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. (See Note A-3.2.1.1.(3)(a)
(8)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 3.2.5.14. and 3.3.1.25., and Sentences 3.2.4.18.(11), 3.2.7.3.(2), 3.3.1.3.(7), 3.4.2.4.(3) and 3.4.4.4.(9). (See Note A-3.2.1.1.(8))
Open OBC Div. B 3.2.1.1. in the code viewer
OBC Div. B 3.2.1.4. Floor Assembly Over Basement
(1)Except as permitted by Sentence 3.2.2.47.(3), 3.2.2.49.(3), 3.2.2.50.(3), 3.2.2.52.(3), 3.2.2.53.(3), 3.2.2.54.(3), 3.2.2.55.(3) or 3.2.2.93.(3), a floor assembly immediately above a basement shall be constructed as a fire separation having a fire-resistance rating conforming to the requirements of Articles 3.2.2.20. to 3.2.2.93. for a floor assembly, but not less than 45 min
(2)All loadbearing walls, columns and arches supporting a floor assembly immediately above a basement shall have a fire-resistance rating not less than that required by Sentence (1) for the floor assembly.
Open OBC Div. B 3.2.1.4. in the code viewer
OBC Div. B 3.2.1.5. Fire Containment in Basements
(1)Except as permitted by Sentences (2) and 3.2.2.15.(3), in a building in which an automatic sprinkler system is not required to be installed by Articles 3.2.2.18., every basement shall
(a)be sprinklered throughout, or
(b)be subdivided into fire compartments not more than 600 m² in area by a fire separation having a fire-resistance rating not less than that required for the floor assembly immediately above the basement.
(2)An open-air storey need not conform to Sentence (1).
Open OBC Div. B 3.2.1.5. in the code viewer
OBC Div. B 3.2.1.2. Storage Garage Considered as a Separate Building
(1)A basement used primarily as a storage garage is permitted to be considered as a separate building for the purposes of Subsection 3.2.2. and Sentences 3.2.5.12.(2) and (3), provided the floor and roof assemblies above the basement and the exterior walls of the basement above the adjoining ground level are constructed as fire separations of noncombustible construction having a fire-resistance rating not less than 2 h and protected in conformance with Clause 3.1.10.2.(4)(a), except as permitted by Sentence (2). (See Notes A-3.1.10.2.(4) and A-3.2.5.12(2))
(2)The exterior wall of a basement that is required to be a fire separation with a fire-resistance rating in accordance with Sentence (1) is permitted to be penetrated by openings that are not protected by closures provided
(a)the storage garage is sprinklered throughout,
(b)every opening in the exterior wall is separated from storeys above the opening by a projection of the floor or roof assembly above the basement, extending not less than
(i)1 m beyond the exterior face of the storage garage if the upper storeys are required to be of noncombustible construction, or
(ii)2 m beyond the exterior face of the storage garage if the upper storeys are permitted to be of combustible construction or encapsulated mass timber construction, or
(c)the exterior walls of any storeys located above the floor or roof assembly referred to in Sentence (1) are recessed behind the outer edge of the assembly by not less than
(i)1 m if the upper storeys are required to be of noncombustible construction, or
(ii)2 m if the upper storeys are permitted to be of combustible construction or encapsulated mass timber construction.
(3)The floor or roof assembly projection referred to in Clause (2)(b) shall have a fire-resistance rating not less than 2 h and shall have no openings within the projection.
Open OBC Div. B 3.2.1.2. in the code viewer
OBC Div. B 3.2.2.5. Applicable Building Height and Area
(1)In determining the fire safety requirements of a building in relation to each of the major occupancies contained therein, the building height and building area of the entire building shall be used.
(2)For the purposes of Sentence (1), a retirement home is deemed to be a separate major occupancy.
Open OBC Div. B 3.2.2.5. in the code viewer
OBC Div. B 3.2.2.6. Multiple Major Occupancies
(1)Except as permitted by Articles 3.2.2.7. and 3.2.2.8., and Sentences 3.2.2.48.(4), 3.2.2.51.(5), 3.2.2.57.(3) and 3.2.2.60.(4) and 3.2.2.93.(5) to (7), in a building containing more than one major occupancy, the requirements of this Subsection for the most restricted major occupancy contained shall apply to the whole building.
(2)For the purposes of Sentence (1), a retirement home is deemed to be a separate major occupancy.
(3)In a building or part thereof constructed in conformance with Article 3.2.2.48., 3.2.2.57. or 3.2.2.93. containing more than one major occupancy, the most restrictive encapsulation requirements of Article 3.1.6.4. and Table 3.2.2.93. for any major occupancy contained within a storey shall apply to the encapsulation required on the interior of a public corridor or exit within that storey.
Open OBC Div. B 3.2.2.6. in the code viewer
OBC Div. B 3.2.2.7. Superimposed Major Occupancies
(1)Except as permitted in Article 3.2.2.8. and Sentences 3.2.2.18.(2), 3.2.2.48.(4), 3.2.2.51.(5), 3.2.2.57.(3), 3.2.2.60.(4) and 3.2.2.93.(5) to (7), in a building in which one major occupancy is located entirely above another major occupancy, the requirements in this Subsection for each portion of the building containing a major occupancy shall apply to that portion as if the entire building were of that major occupancy.
(2)If one major occupancy is located above another major occupancy, the fire-resistance rating of the floor assembly between the major occupancies shall be determined on the basis of the requirements of this Subsection for the lower major occupancy. (See also Article 3.1.3.1.)
(3)For the purposes of Sentences (1) and (2), a retirement home is deemed to be a separate major occupancy.
(4)In a building or part thereof constructed in conformance with Article 3.2.2.48., 3.2.2.57. or 3.2.2.93., if one major occupancy is located above another major occupancy,
(a)the most restrictive encapsulation requirements of Article 3.1.6.4. and Table 3.2.2.93. for any major occupancy contained within the building shall apply to the encapsulation required on the interior of vertical service spaces and exit stairs, and
(b)the encapsulation requirements of Article 3.1.6.4. and Table 3.2.2.93. for a mass timber floor assembly between the major occupancies shall be determined on the basis of the requirements for,
(i)the upper major occupancy for the encapsulation of the upper surface of the mass timber floor assembly, and
(ii)the lower major occupancy for the encapsulation of the underside of the mass timber floor assembly.
Open OBC Div. B 3.2.2.7. in the code viewer

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OBC Div. B 3.2.2.8. Exceptions for Major Occupancies
(1)In a building in which the aggregate area of all major occupancies in a particular Group or Division is not more than 10% of the floor area of the storey in which they are located, these major occupancies need not be considered as major occupancies for the purposes of this Subsection, provided they are not classified as Group F, Division 1 or 2 occupancies.
(2)For the purposes of Sentence (1), a retirement home is deemed to be a separate major occupancy.
(3)A helicopter landing area on the roof of a building need not be considered a major occupancy for purposes of Subsection 3.2.2. where such landing area is not more than 10% of the area of the roof.
Open OBC Div. B 3.2.2.8. in the code viewer
OBC Div. B 3.2.2.10. Streets
(1)Every building shall face a street located in conformance with the requirements of Articles 3.2.5.4 and 3.2.5.5 for access routes.
(2)For the purposes of Subsections 3.2.2. and 3.2.5. an access route conforming to Subsection 3.2.5. is permitted to be considered as a street.
(3)A building conforming to Article 3.2.2.51. or 3.2.2.60. is considered to face one street, where
(a)not less than 25% of the building perimeter is located within 15 m of a street or streets, or
(b)not less than 10% of the building perimeter is located within 15 m of a street or streets, provided the exterior cladding conforms to Sentence 3.1.4.8.(2).
(4)A building is considered to face 2 streets provided not less than 50% of the building perimeter is located within 15 m of the street or streets.
(5)A building is considered to face 3 streets provided not less than 75% of the building perimeter is located within 15 m of the street or streets.
(6)Enclosed spaces, tunnels, bridges and similar structures, even though used for vehicular or pedestrian traffic, are not considered as streets for the purpose of this Part.
Open OBC Div. B 3.2.2.10. in the code viewer
OBC Div. B 3.2.2.51. Group C, up to 6 Storeys, Sprinklered, Combustible Construction
(1)A building classified as Group C, other than a retirement home, is permitted to conform to Sentence (2) provided
(a)it is sprinklered throughout,
(b)it is not more than 6 storeys in building height,
(c)it has a height of not more than 18 m, measured between the floor of the first storey and the uppermost floor level that does not serve a rooftop enclosure for elevator machinery, a stairway or a service room used only for service to the building, and
(d)it has a building area of not more than
(i)9,000 m² if 1 storey in building height,
(ii)4,500 m² if 2 storeys in building height,
(iii)3,000 m² if 3 storeys in building height,
(iv)2,250 m² if 4 storeys in building height,
(v)1,800 m² if 5 storeys in building height, or
(vi)1,500 m² if 6 storeys in building height.
(2)Buildings referred to in Sentence (1) are permitted to be of combustible construction or noncombustible construction used singly or in combination, and
(a)except as permitted by Sentence (3), floor assemblies shall be fire separations with a fire-resistance rating not less than 1 h.
(b)roof assemblies shall have a fire-resistance rating not less than 1 h,
(c)except as provided by Sentence (4), where the roof assembly has a height greater than 25 m measured from the floor of the first storey to the highest point of the roof assembly, the roof assembly shall be constructed of noncombustible construction, or fire-retardant-treated wood conforming to Article 3.1.4.5.,
(d)mezzanines shall have a fire-resistance rating not less than 1 h, and
(e)loadbearing walls, columns and arches shall have a fire-resistance rating not less than that required for the supported assembly.
(3)In a building that contains dwelling units that have more than one storey, subject to the requirements of Sentence 3.3.4.2.(3), the floor assemblies, including those over basements, which are entirely contained within these dwelling units, shall have a fire-resistance rating not less than 1 h but need not be constructed as fire separations.
(4)Where buildings conforming to Sentence (2) include non-contiguous roof assemblies at different elevations, the roof assemblies are permitted to be evaluated separately to determine which ones are required to be constructed in accordance with Clause (2)(c).
(5)Group A, Division 2 major occupancies, Group E major occupancies and storage garages located in a building or part thereof within the scope of this Article are permitted to be constructed in accordance with this Article, provided
(a)the Group A, Division 2 major occupancy and Group E major occupancy are located below the third storey, and
(b)the storage garage is located below the fourth storey. (See also Article 4.4.2.1.) (See Note A-3.2.2.51.(5) and 3.2.2.60.(4))
Open OBC Div. B 3.2.2.51. in the code viewer
OBC Div. B 3.2.2.60. Group D, up to 6 Storeys, Sprinklered
(1)A building classified as Group D is permitted to conform to Sentence (2) provided
(a)it is sprinklered throughout,
(b)it is not more than 6 storeys in building height,
(c)it has a height of not more than 18 m measured between the floor of the first storey and the uppermost floor level that does not serve a rooftop enclosure for elevator machinery, a stairway or a service room used only for service to the building, and
(d)it has a building area of not more than
(i)18,000 m² if 1 storey in building height,
(ii)9,000 m² if 2 storeys in building height,
(iii)6,000 m² if 3 storeys in building height,
(iv)4,500 m² if 4 storeys in building height,
(v)3,600 m² if 5 storeys in building height, or
(vi)3,000 m² if 6 storeys in building height.
(2)The building referred to in Sentence (1) is permitted to be of combustible construction or noncombustible construction used singly or in combination, and
(a)floor assemblies shall be fire separations with a fire-resistance rating not less than 1 h,
(b)roof assemblies shall have a fire-resistance rating not less than 1 h,
(c)except as provided by Sentence (3), where the roof assembly has a height greater than 25 m measured from the floor of the first storey to the highest point of the roof assembly, the roof assembly shall be constructed of noncombustible construction or fire-retardant-treated wood conforming to Article 3.1.4.5.,
(d)mezzanines shall have a fire-resistance rating not less than 1 h, and
(e)loadbearing walls, columns and arches shall have a fire-resistance rating not less than that required for the supported assembly.
(3)Where buildings conforming to Sentence (2) include non-contiguous roof assemblies at different elevations, the roof assemblies are permitted to be evaluated separately to determine which ones are required to be constructed in accordance with Clause (2)(c).
(4)Group A, Division 2 major occupancies, Group E major occupancies, Group F, Division 2 and 3 major occupancies and storage garages located in a building or part thereof within the scope of this Article are permitted to be constructed in accordance with this Article, provided
(a)the Group A, Division 2 major occupancy, Group E major occupancy and Group F, Division 2 or 3 major occupancy are located below the third storey, and
(b)storage garages are located below the fourth storey. (See also Article 4.4.2.1.)(See Note A-3.2.2.51.(5) and 3.2.2.60.(4))
Open OBC Div. B 3.2.2.60. in the code viewer
OBC Div. A 1.4.1.2.(1) Street
Street means any highway, road, boulevard, square or other improved thoroughfare that is 9 m or more in width, that has been dedicated or deeded for public use and that is accessible to fire department vehicles and equipment.
Open OBC Div. A 1.4.1.2.(1) in the code viewer
OBC Div. B 3.2.2.9. Crawl Spaces
(1)For the purposes of Articles 3.1.11.6., 3.2.1.4. and 3.2.1.5., a crawl space shall be considered as a basement if it is
(a)more than 1.8 m high between the lowest part of the floor assembly and the ground or other surface below,
(b)used for any occupancy,
(c)used for the passage of flue pipes, or
(d)used as a plenum in combustible construction.
(2)A floor assembly immediately above a crawl space is not required to be constructed as a fire separation and is not required to have a fire-resistance rating provided the crawl space is not required to be considered as a basement by Sentence (1).
Open OBC Div. B 3.2.2.9. in the code viewer
OBC Div. B 3.2.2.13. Occupancy on Roof
(1)A portion of a roof that supports an occupancy shall be constructed in conformance with the fire separation requirements of Articles 3.2.2.20. to 3.2.2.93. for floor assemblies.
Open OBC Div. B 3.2.2.13. in the code viewer
OBC Div. B 3.2.2.18. Automatic Sprinkler System Required
(1)Except as permitted by Sentence (2), an automatic sprinkler system conforming to the requirements of Articles 3.2.4.7., 3.2.4.8., 3.2.4.9. and 3.2.5.12. shall be installed throughout a building regulated by one or more of Articles 3.2.2.20., 3.2.2.21., 3.2.2.22., 3.2.2.23., 3.2.2.24., 3.2.2.26., 3.2.2.27., 3.2.2.29., 3.2.2.31., 3.2.2.33., 3.2.2.36., 3.2.2.37., 3.2.2.38., 3.2.2.39., 3.2.2.40., 3.2.2.41., 3.2.2.42., 3.2.2.43., 3.2.2.44., 3.2.2.45., 3.2.2.46., 3.2.2.47., 3.2.2.48., 3.2.2.49., 3.2.2.51., 3.2.2.52., 3.2.2.55., 3.2.2.55A., 3.2.2.55B., 3.2.2.55C., 3.2.2.55D., 3.2.2.55.E., 3.2.2.56., 3.2.2.57., 3.2.2.59., 3.2.2.60., 3.2.2.61., 3.2.2.63., 3.2.2.65., 3.2.2.66., 3.2.2.67., 3.2.2.69., 3.2.2.71., 3.2.2.72., 3.2.2.73., 3.2.2.74., 3.2.2.76., 3.2.2.77., 3.2.2.79., 3.2.2.81., 3.2.2.82., 3.2.2.84., 3.2.2.86., 3.2.2.88., 3.2.2.90. and 3.2.2.93.
(2)If a storey in a building or a floor area is required to have an automatic sprinkler system installed throughout in accordance with one or more of Articles 3.2.2.20. to 3.2.2.93. or Section 3.3., the automatic sprinkler system shall also be installed throughout all lower storeys in the building notwithstanding permission in Articles 3.2.2.20. to 3.2.2.93. to construct one or more of those storeys without installing automatic sprinkler protection. (See Note A-3.2.2.18.(2))
Open OBC Div. B 3.2.2.18. in the code viewer
OBC Div. B 3.2.2.17. Roof Assemblies and Mezzanines in Gymnasiums, Swimming Pools, Arenas and Rinks
(1)The requirements for a roof assembly to have a fire-resistance rating stated in Articles 3.2.2.25., 3.2.2.30. and 3.2.2.32. are permitted to be waived for gymnasiums, swimming pools, arenas, and rinks, provided
(a)the roof carries no loads other than normal roof loads, including permanent access walks, and ventilating, sound and lighting equipment, and
(b)except as provided in Sentence (3), no part of the roof assembly is less than 6 m above the main floor or balcony. (See Note A-3.2.2.17.(1))
(2)The requirements for a mezzanine to have a fire-resistance rating stated in Articles 3.2.2.25., 3.2.2.30. and 3.2.2.32. are permitted to be waived for gymnasiums, swimming pools, arenas, and rinks, provided
(a)the mezzanine is not required to be considered as a storey as per Sentences 3.2.1.1.(3) to (5),
(b)the mezzanine is used only for ventilating, sound and lighting equipment, and
(c)except as provided in Sentence (3), no part of the mezzanine is less than 6 m above the main floor or balcony.
(3)The restrictions concerning minimum distance stated in Clauses (1)(b) and (2)(c) shall not apply to
(a)an inclined and stepped floor ascending from the main floor that is used for seating purposes only, or
(b)a balcony used for seating purposes only.
Open OBC Div. B 3.2.2.17. in the code viewer
OBC Div. A 1.4.1.2.(1) Impeded egress zone
Impeded egress zone means a supervised area in which occupants have free movement but require the release, by security personnel, of security doors at the boundary before they are able to leave the area, but does not include a contained use area.
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OBC Div. B 3.2.2.19. Buildings Containing Impeded Egress Zones
(1)A building containing an impeded egress zone and conforming to the appropriate requirements of Articles 3.2.2.20. to 3.2.2.93. is not required to conform to the requirements of Articles 3.2.2.36. and 3.2.2.37. for a Group B, Division 1 major occupancy provided
(a)the building is sprinklered throughout,
(b)it is not more than 1 storey in building height,
(c)it does not include
(i)a contained use area,
(ii)sleeping accommodation,
(iii)a high-hazard industrial occupancy, or
(iv)a mercantile occupancy,
(d)the building area is not more than 6,400 m² if the building includes a medium-hazard industrial occupancy,
(e)the impeded egress zone does not extend beyond the boundaries of the fire compartment in which it is located, and
(f)the occupant load of the impeded egress zone is not more than 100.
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OBC Div. B 3.2.2.25. Group A, Division 2, up to 2 Storeys
(1)A building classified as Group A, Division 2 is permitted to conform to Sentence (2) provided
(a)it is not more than 2 storeys in building height, and
(b)it has a building area not more than the value in Table 3.2.2.25.
(2)The building referred to in Sentence (1) is permitted to be of combustible construction or noncombustible construction used singly or in combination, and
(a)floor assemblies shall be fire separations and, if of combustible construction, shall have a fire-resistance rating not less than 45 min,
(b)except as permitted by Article 3.2.2.17., mezzanines shall have, if of combustible construction, a fire-resistance rating not less 45 min,
(c)except as permitted by Article 3.2.2.17., roof assemblies shall have, if of combustible construction, a fire-resistance rating not less than 45 min, except that in a building not more than 1 storey in building height, the fire-resistance rating is permitted to be waived provided the roof assembly is constructed as a fire-retardant-treated wood roof system conforming to Article 3.1.14.1., and the building area is not more than
(i)800 m² if facing one street,
(ii)1,000 m² if facing 2 streets, or
(iii)1,200 m² if facing 3 streets, and
(d)loadbearing walls, columns and arches supporting an assembly required to have a fire-resistance rating shall
(i)have a fire-resistance rating not less than 45 min, or
(ii)be of noncombustible construction.
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OBC Div. B 3.2.2.54. Group C, up to 3 Storeys
(1)A building classified as Group C, other than a retirement home, is permitted to conform to Sentence (2) provided
(a)it is not more than 3 storeys in building height, and
(b)it has a building area not more than the value in Table 3.2.2.54.
(2)The building referred to in Sentence (1) is permitted to be of combustible construction or noncombustible construction used singly or in combination, and
(a)except as permitted by Sentences (3) and (4), floor assemblies shall be fire separations with a fire-resistance rating not less than 45 min,
(b)mezzanines shall have, if of combustible construction, a fire-resistance rating not less than 45 min, and
(c)loadbearing walls, columns and arches shall have a fire-resistance rating not less than that required for the supported assembly.
(3)In a building that contains dwelling units that have more than one storey, subject to the requirements of Sentence 3.3.4.2.(3), the floor assemblies, including floors over basements, that are entirely contained within these dwelling units, shall have a fire-resistance rating not less than 45 min but need not be constructed as fire separations.
(4)In a building in which there is no dwelling unit above another dwelling unit, the fire-resistance rating for floor assemblies entirely within the dwelling unit is waived.
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OBC Div. B 3.2.2.55. Group C, up to 3 Storeys, Sprinklered
(1)A building classified as Group C, other than a retirement home, is permitted to conform to Sentence (2) provided
(a)except as permitted by Sentences 3.2.2.7.(1) and 3.2.2.18.(2), the building is sprinklered throughout,
(b)it is not more than 3 storeys in building height, and
(c)it has a building area not more than
(i)5,400 m² if 1 storey in building height,
(ii)2,700 m² if 2 storeys in building height, or
(iii)1,800 m² if 3 storeys in building height.
(2)The building referred to in Sentence (1) is permitted to be of combustible construction or noncombustible construction used singly or in combination, and
(a)except as permitted by Sentences (3) and (4), floor assemblies shall be fire separations with a fire-resistance rating not less than 45 min,
(b)mezzanines shall have, if of combustible construction a fire-resistance rating not less than 45 min, and
(c)loadbearing walls, columns and arches shall have a fire-resistance rating not less than that required for the supported assembly.
(3)In a building that contains dwelling units that have more than one storey, subject to the requirements of Sentence 3.3.4.2.(3), the floor assemblies, including floors over basements, that are entirely contained within these dwelling units, shall have a fire-resistance rating not less than 45 min but need not be constructed as fire separations.
(4)In a building in which there is no dwelling unit above another dwelling unit, the fire-resistance rating for floor assemblies entirely within the dwelling unit is waived.
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OBC Div. B 3.2.2.62. Group D, up to 3 Storeys
(1)A building classified as Group D is permitted to conform to Sentence (2) provided
(a)it is not more than 3 storeys in building height, and
(b)it has a building area not more than the value in Table 3.2.2.62.
(2)The building referred to in Sentence (1) is permitted to be of combustible construction or noncombustible construction used singly or in combination, and
(a)floor assemblies shall be fire separations and, if of combustible construction, shall have a fire-resistance rating not less than 45 min,
(b)mezzanines shall have, if of combustible construction, a fire-resistance rating not less than 45 min,
(c)roof assemblies shall have, if of combustible construction, a fire-resistance rating not less than 45 min, except that in a building not more than 1 storey in building height, the fire-resistance rating is permitted to be waived provided the roof assembly is constructed as a fire-retardant-treated wood roof system conforming to Article 3.1.14.1., and the building area is not more than
(i)2,400 m² if facing one street,
(ii)3,000 m² if facing 2 streets, or
(iii)3,600 m² if facing 3 streets, and
(d)loadbearing walls, columns and arches supporting an assembly required to have a fire-resistance rating shall
(i)have a fire-resistance rating not less than 45 min, or
(ii)be of noncombustible construction.
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OBC Div. B 3.2.2.66. Group E, Any Height, Any Area, Sprinklered
(1)Except as permitted by Articles 3.2.2.67. to 3.2.2.71. and 3.2.2.93., a building classified as Group E shall conform to Sentence (2).
(2)Except as permitted by Article 3.2.2.16., the building referred to in Sentence (1) shall be of noncombustible construction, and
(a)except as permitted by Sentences 3.2.2.7.(1) and 3.2.2.18.(2), the building shall be sprinklered throughout,
(b)floor assemblies shall be fire separations with a fire-resistance rating not less than 2 h,
(c)mezzanines shall have a fire-resistance rating not less 1 h, and
(d)loadbearing walls, columns and arches shall have a fire-resistance rating not less than that required for the supported assembly.
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OBC Div. B 3.2.2.70. Group E, up to 2 Storeys
(1)A building classified as Group E is permitted to conform to Sentence (2) provided
(a)it is not more than 2 storeys in building height, and
(b)it has a building area not more than the value in Table 3.2.2.70.
(2)The building referred to in Sentence (1) is permitted to be of combustible construction or noncombustible construction used singly or in combination, and
(a)floor assemblies shall be fire separations with a fire-resistance rating not less than 45 min, and
(b)loadbearing walls, columns and arches shall have a fire-resistance rating not less than that required for the supported assembly.
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OBC Div. B 3.2.2.75. Group F, Division 1, One Storey
(1)A building classified as Group F, Division 1 is permitted to be of combustible construction or noncombustible construction used singly or in combination provided
(a)it is not more than 1 storey in building height, and
(b)it has a building area not more than 800 m².
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