Building size and construction relative to occupancy (Large Buildings)

Last updated October 22, 2026

Values this chapter turns on

height limit for 6 storey combustible Group C or D: 18 m; height limit for 6 storey combustible Group C or D
minimum width of a street for building area tables: 9 m; minimum width of a street for building area tables
of perimeter within 15 m of streets to face 2 streets: 50%; of perimeter within 15 m of streets to face 2 streets
max area, sprinklered 1 storey F-2 building: 9,600 m²; max area, sprinklered 1 storey F-2 building

Subsection 3.2.2. is the heart of Part 3 design and the most heavily used part of the code on a Large Buildings exam. For each major occupancy it offers a ladder of "construction articles" (3.2.2.20. to 3.2.2.93.). Each one says: if the building is no taller than X storeys, no larger than Y m² and (sometimes) sprinklered, it may be built of a stated construction type with stated fire-resistance ratings. Your job on the exam is to find the article that fits, then read off what it requires. Subsection 3.2.1. sets the ground rules for counting storeys first.

Counting building height (3.2.1.)

Building height is the number of storeys between the roof and the floor of the first storey. Article 3.2.1.1. removes several things from the count:

a rooftop enclosure used only for elevator machinery, a stairway or a service room;
space under arena-type seating used only for dressing rooms, concessions and similar uses;
a mezzanine that stays open above (no partitions over 1,070 mm) and whose non-superimposed area is not more than 40% of the room's open area (Sentence (3));
other mezzanines whose total is not more than 10% of the floor area, and not more than 10% of a suite's area (Sentence (4));
inspection platforms and maintenance catwalks not used for storage.

Any mezzanine level stacked partly or wholly above the first mezzanine level counts as a storey (Sentence (5)), and its floor must then meet the floor assembly rules of the applicable construction article (3.2.1.6.).

Other general rules in 3.2.1.:

Rule	Key value	Source
Basement storage garage treated as a separate building	2 h noncombustible fire separations above and at exposed walls	3.2.1.2.
Projection or recess protecting unprotected garage openings	1 m (noncombustible above), 2 m (combustible or encapsulated mass timber above)	3.2.1.2.
Roof treated as part of an exterior wall	pitched 60° or more, next to occupied space	3.2.1.3.
Floor over a basement	fire separation, rated as the article requires, never under 45 min	3.2.1.4.
Unsprinklered basement in a building not required to be sprinklered	fire compartments of not more than 600 m²	3.2.1.5.

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Multiple major occupancies (3.2.2.4. to 3.2.2.8.)

When a building has more than one major occupancy:

Always use the building height and building area of the entire building (3.2.2.5.).
If the occupancies sit side by side, the requirements for the most restricted occupancy apply to the whole building (3.2.2.6.).
If one occupancy sits entirely above another, each portion is designed as if the whole building were that occupancy, and the floor between them is rated for the lower occupancy (3.2.2.7.). Also check Table 3.1.3.1. for the separation between major occupancies.
An occupancy group that totals not more than 10% of the floor area of its storey can be ignored for 3.2.2., unless it is Group F, Division 1 or 2 (3.2.2.8.).

A retirement home counts as a separate major occupancy for all of these rules (3.2.2.4.). Some articles, for example 3.2.2.51., 3.2.2.60. and the encapsulated mass timber articles, let certain lower occupancies (assembly, mercantile, storage garages) be built to the main article if they stay below a stated storey.

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Facing streets (3.2.2.10.)

Many tables give larger areas when a building faces more streets. A street is a public thoroughfare at least 9 m wide that fire trucks can use (Div. A definition), and a compliant access route may count as a street (3.2.2.10.).

Building faces	Share of perimeter within 15 m of a street
1 street, 3.2.2.51. or 3.2.2.60. buildings	25%, or 10% with cladding to 3.1.4.8.(2)
2 streets	50%
3 streets	75%

Tunnels, bridges and enclosed spaces never count as streets.

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Sprinklers and below-grade storeys

Article 3.2.2.18. lists every construction article that demands a sprinkler system throughout. Its second Sentence is a common trap: once any storey must be sprinklered, all lower storeys must be too, even if their own article would allow none.

A building that goes more than one storey below ground needs sprinklered basements and fire separation floors below ground rated 3 h for Group E or Group F, Division 1 or 2, and 2 h otherwise (3.2.2.15.). An occupied roof is built like a floor assembly (3.2.2.13.).

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How the construction articles are laid out

For each Group the articles start with an "any height, any area, sprinklered" noncombustible article, then step down to smaller, less demanding options. Headings tell you the essentials: Group, storeys, "increased area", "sprinklered", construction type. Areas come either from the text (usually for sprinklered articles) or from a table by storeys and streets (usually unsprinklered).

A few anchors worth remembering (check the article before you rely on them):

Article	Group	Storeys	Sprinklered	Construction
3.2.2.52.	C	up to 4	yes	combustible allowed
3.2.2.54.	C	up to 3	no	combustible allowed
3.2.2.58.	D	up to 6	no	noncombustible
3.2.2.60.	D	up to 6, 18 m	yes	combustible allowed
3.2.2.68.	E	up to 3	no	combustible allowed
3.2.2.75.	F1	1	no	combustible, 800 m²
3.2.2.92.	F3 open-air garage	22 m	no	noncombustible, no ratings
3.2.2.93.	several	by table	yes	encapsulated mass timber

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Worked examples

Example 1: Group D office. 4 storeys, sprinklered, 4,000 m², light wood frame wanted, top floor 13 m above the first floor. Article 3.2.2.61. (up to 4 storeys, sprinklered) caps area at 3,600 m², so it fails. Article 3.2.2.60. allows 4,500 m² at 4 storeys and up to 18 m, so it works, provided the street rule of 3.2.2.10.(3) is met. Then read Sentence (2): 1 h floors and roof, rated loadbearing supports, and the roof rule for heights over 25 m.

Example 2: Group C apartments. 3 storeys, 1,100 m², faces 2 streets, combustible. Unsprinklered options: 3.2.2.54. allows 750 m² (fails); 3.2.2.53. allows 1,000 m² (fails); 3.2.2.50. allows 5,000 m² but needs noncombustible construction. Sprinklered: 3.2.2.55. allows 1,800 m² at 3 storeys with combustible construction and 45 min floors. The designer chooses between noncombustible construction and sprinklers.

Example 3: Group F, Division 2 warehouse. 1 storey, 5,000 m². Table 3.2.2.78. tops out at 1,500 m², and 3.2.2.81. (sprinklered) at 4,500 m². Article 3.2.2.79. allows 9,600 m² for 1 storey if sprinklered, with combustible construction permitted. A medium-hazard building this size must be sprinklered.

Example 4: mixed use. 3 storeys, Group E on the first storey and Group C above, 900 m², unsprinklered, faces 2 streets. The store is checked as a 3 storey Group E building: Table 3.2.2.68. gives 1,000 m², so it passes. The apartments are checked as a 3 storey Group C building: 3.2.2.54. gives only 750 m², but 3.2.2.53. gives 1,000 m², so it passes with 1 h floors and roof. The floor between the store and the apartments takes its rating from the Group E article.

Common traps

Using only the storeys an occupancy occupies. The height and area of the entire building always apply.
Forgetting the 18 m height limit in 3.2.2.51. and 3.2.2.60., measured to the uppermost floor level, not the roof.
Mixing up 3.2.2.62. and 3.2.2.63. (unsprinklered and sprinklered Group D, up to 3 storeys) or similar neighbours. Read the heading.
Interpolating Table 3.2.2.93. Its note forbids it.

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
Counting building height (3.2.1.)	Building height is the number of storeys between the roof and the floor of the first storey.
Multiple major occupancies (3.2.2.4. to 3.2.2.8.)	A retirement home counts as a separate major occupancy for all of these rules.
Facing streets (3.2.2.10.)	Many tables give larger areas when a building faces more streets.
Sprinklers and below-grade storeys	A building that goes more than one storey below ground needs sprinklered basements and fire separation floors below ground rated 3 h for Group E or Group F, Division 1 or 2, and 2…
How the construction articles are laid out	For each Group the articles start with an "any height, any area, sprinklered" noncombustible article, then step down to smaller, less demanding options.

Counting building height (3.2.1.)
Building height is the number of storeys between the roof and the floor of the first storey.
Multiple major occupancies (3.2.2.4. to 3.2.2.8.)
A retirement home counts as a separate major occupancy for all of these rules.
Facing streets (3.2.2.10.)
Many tables give larger areas when a building faces more streets.
Sprinklers and below-grade storeys
A building that goes more than one storey below ground needs sprinklered basements and fire separation floors below ground rated 3 h for Group E or Group F, Division 1 or 2, and 2…
How the construction articles are laid out
For each Group the articles start with an "any height, any area, sprinklered" noncombustible article, then step down to smaller, less demanding options.

Usual exam traps

Using only the storeys an occupancy occupies. The height and area of the entire building always apply.
Forgetting the 18 m height limit in 3.2.2.51. and 3.2.2.60., measured to the uppermost floor level, not the roof.
Mixing up 3.2.2.62. and 3.2.2.63. (unsprinklered and sprinklered Group D, up to 3 storeys) or similar neighbours. Read the heading.
Interpolating Table 3.2.2.93. Its note forbids it.

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Questions on Building size and construction relative to occupancy (3.2.1, 3.2.2), in the exam format, every answer explained and cited to its article. Sign in to start; a free account gets the free questions.

Practice this chapter Free Large Buildings quiz

Code cited in this chapter

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

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 3.2.1.6. Mezzanines
(1)The floor assembly of a mezzanine that is required to be considered as a storey in calculating the building height shall be constructed in conformance with the fire separation requirements for floor assemblies in Articles 3.2.2.20. to 3.2.2.93.
Open OBC Div. B 3.2.1.6. 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 3.2.1.3. Roof Considered as a Wall
(1)For the purposes of this Section any part of a roof that is pitched at an angle of 60° or more to the horizontal and is adjacent to a space intended for occupancy within a building shall be considered as part of an exterior wall of the building.
Open OBC Div. B 3.2.1.3. 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 3.2.2.5. 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

Show all 26 articles

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
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 3.2.2.4. Buildings with Multiple Major Occupancies
(1)The requirements restricting fire spread and collapse for a building of a single major occupancy classification are provided in this Subsection according to its building height and building area.
(2)If a building contains more than one major occupancy, classified in more than one Group or Division, the requirements of this Subsection concerning building size and construction relative to major occupancy shall apply according to Articles 3.2.2.5. to 3.2.2.8.
(3)For the purposes of Sentences (1) and (2), a retirement home is deemed to be a separate major occupancy.
Open OBC Div. B 3.2.2.4. 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 3.2.2.10. 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 3.2.2.18. 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 3.2.2.15. Storeys Below Ground
(1)If a building is erected entirely below the adjoining finished ground level and does not extend more than one storey below that ground level, the minimum precautions against fire spread and collapse shall be the same as are required for basements under a building of 1 storey in building height having the same occupancy and building area.
(2)If any portion of a building is erected entirely below the adjoining finished ground level and extends more than 1 storey below that ground level, the following minimum precautions against fire spread and collapse shall be taken:
(a)except as permitted by Sentence (3), the basements shall be sprinklered throughout,
(b)a floor assembly below the ground level shall be constructed as a fire separation with a fire-resistance rating not less than
(i)3 h if the basements are used as Group E or Group F, Division 1 or 2 occupancies, or
(ii)2 h if the basements are not used as Group E or Group F, Division 1 or 2 occupancies, and
(c)all loadbearing walls, columns and arches shall have a fire-resistance rating not less than that required for the construction that they support.
(3)If the first storey of a building is not required to be sprinklered, sprinklers are not required in the storey immediately below the first storey, provided the storey below
(a)contains only residential occupancies, and
(b)has at least one unobstructed access opening conforming to Sentence 3.2.5.1.(2) installed on that storey for each 15 m of wall length in at least one wall required by this Subsection to face a street.
Open OBC Div. B 3.2.2.15. 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 3.2.2.52. Group C, up to 4 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 4 storeys in building height, and
(c)it has a building area not more than
(i)7,200 m² if 1 storey in building height,
(ii)3,600 m² if 2 storeys in building height,
(iii)2,400 m² if 3 storeys in building height, or
(iv)1,800 m² if 4 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 1 h,
(b)mezzanines shall have a fire-resistance rating not less than 1 h, 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 1 h 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 3.2.2.54. 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 3.2.2.58. Group D, up to 6 Storeys
(1)A building classified as Group D is permitted to conform to Sentence (2) provided
(a)it is not more than 6 storeys in building height, and
(b)it has a building area not more than the value in Table 3.2.2.58.
(2)The building referred to in Sentence (1) shall be of noncombustible construction, and
(a)floor assemblies shall be fire separations with a fire-resistance rating not less than 1 h,
(b)mezzanines shall have a fire-resistance rating not less than 1 h,
(c)roof assemblies shall have a fire-resistance rating not less than 1 h, except that in a building not more than 1 storey in building height this requirement is waived, 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 3.2.2.60. 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))
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OBC Div. B 3.2.2.68. Group E, up to 3 Storeys
(1)A building classified as Group E 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 3.2.2.68.
(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,
(b)mezzanines shall have, if of combustible construction, a fire-resistance rating not less than 45 min,
(c)roof assemblies shall have 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 of noncombustible construction or is constructed as a fire-retardant-treated wood roof system conforming to Article 3.1.14.1.,
(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, and
(e)loadbearing walls, columns and arches supporting a fire separation shall have a fire-resistance rating not less than that required for the fire separation.
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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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OBC Div. B 3.2.2.92. Group F, Division 3, Storage Garages up to 22 m High
(1)A building used as a storage garage with all storeys constructed as open-air storeys and having no other occupancy above it is permitted to have its floor, wall, ceiling and roof assemblies constructed without a fire-resistance rating provided it is
(a)of noncombustible construction,
(b)not more than 22 m high, measured between grade and the ceiling level of the top storey,
(c)not more than 10,000 m² in building area, and
(d)designed so that every portion of each floor area is within 60 m of an exterior wall opening.
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OBC Div. B 3.2.2.93. Encapsulated Mass Timber Construction , Various Occupancies, Heights and Areas, Sprinklered
(1)A building that is classified as Group A, Division 2, Group B, Division 3, Group C other than a retirement home, Group D, Group E, or Group F, Division 2 or 3, 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)the building has a building height not exceeding the number of storeys shown in Table 3.2.2.93. for the applicable major occupancy and minimum encapsulation rating,
(c)the building has a maximum height that conforms to the value shown in Table 3.2.2.93. for the applicable major occupancy and minimum encapsulation rating that is 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,
(d)the building has a maximum building area that conforms to the value shown in Table 3.2.2.93. for the applicable major occupancy, and
(e)except as provided in Sentences 3.1.6.3.(4) and 3.1.6.7.(1) and Article 3.1.6.4., the encapsulation rating conforms to the value shown in Table 3.2.2.93. for the applicable major occupancy and maximum building height. (See Note A-3.2.2.93.(1) and Table 3.2.2.93. See also Articles 3.2.2.48. and 3.2.2.57.)
(2)Except as provided in Article 3.2.2.16., the building referred to in Sentence (1) is permitted to be of encapsulated mass timber construction or noncombustible construction used singly or in combination, and,
(a)except as provided in Sentence (3), floor assemblies shall be fire separations with a fire-resistance rating not less than 2 h.
(b)mezzanines shall have a fire-resistance rating not less than 1 h, 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 classified as a Group C major occupancy 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 1 h but need not be constructed as fire separations.
(4)In buildings referred to in Sentence (1) where the roof assembly of an exit stairway or vertical service space used as an elevator hoistway has a height greater than 55 m measured from grade to the highest point of the roof assembly, the enclosure for the stairway or hoistway shall be of encapsulated mass timber construction or constructed of concrete.
(5)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 and the corresponding Group A, Division 2, Group C, or Group D major occupancy requirements contained in Table 3.2.2.93., provided
(a)the Group E major occupancy is located below the third storey, and
(b)the storage garage is located below the fifth storey. (See also Article 4.4.2.1.)(See Note A-3.2.2.48.(4), 3.2.2.57.(3) and 3.2.2.93.(5) to (7))
(6)Group A, Division 2 major occupancies located in a building or part of a building within the scope of this Article are permitted to be constructed in accordance with this Article and the corresponding Group C, or Group D major occupancy requirements contained in Table 3.2.2.93., provided they are located below the fourth storey. (See Note A-3.2.2.48.(4), 3.2.2.57.(3) and 3.2.2.93.(5) to (7))
(7)Group F, Division 2 and 3 major occupancies located in a building or part thereof within the scope of this Article are permitted to be constructed in accordance with this Article and the corresponding Group D major occupancy requirements contained in Table 3.2.2.93., provided they are located below the third storey. (See Note A-3.2.2.48.(4), 3.2.2.57.(3) and 3.2.2.93.(5) to (7))
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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 3.2.2.79. Group F, Division 2, up to 4 Storeys, Sprinklered
(1)A building classified as Group F, Division 2 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 4 storeys in building height, and
(c)it has a building area not more than
(i)9,600 m² if 1 storey in building height,
(ii)4,800 m² if 2 storeys in building height,
(iii)3,200 m² if 3 storeys in building height, or
(iv)2,400 m² if 4 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 45 min,
(b)mezzanines shall have, if of combustible construction, a fire-resistance rating not less than 45 min,
(c)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, and
(d)loadbearing walls, columns and arches supporting a fire separation shall have a fire-resistance rating not less than that required for the supported assembly.
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