Classification, construction types and fire-resistance (3.1) (Large Buildings)

Last updated October 22, 2026

Values this chapter turns on

separation between F-1 and Group D or E: 3 h; separation between F-1 and Group D or E
min mass timber floor or wall, one side exposed: 96 mm; min mass timber floor or wall, one side exposed
min square mass timber column, four sides exposed: 224 mm; min square mass timber column, four sides exposed
max combustible ceiling finish, noncombustible building: 25 mm; max combustible ceiling finish, noncombustible building

Section 3.1. is the toolkit the rest of Part 3 relies on: classification, occupancy separations, construction types, ratings, closures, firewalls, finishes and occupant load. The high-building finish rules in 3.1.13.7. are excluded from this exam.

Classification and multiple occupancies

Every building or part is classified by major occupancy under Table 3.1.2.1., and a building with several major occupancies is classified by all of them (OBC Div. B 3.1.2.1.). Occupancies in the same Group (or same Division, where the Group has Divisions) count as one major occupancy (OBC Div. B 3.1.2.2.).

The special classification Articles are favourite exam material:

Situation	Classification allowed	Source
Arena used occasionally for trade shows	A-3	3.1.2.3.
Police station with detention quarters, 1 storey, up to 600 m²	B-2 instead of B-1	3.1.2.4.
Care occupancy suite, up to 10 sleeping, up to 2 needing help to evacuate	Group C	3.1.2.5.
Baled combustible fibre storage	F-2	3.1.2.6.
Restaurant for up to 30 persons	Group E	3.1.2.7.

Separations. Major occupancies are separated by fire separations rated per Table 3.1.3.1. (OBC Div. B 3.1.3.1.). Typical values: 1 h between most Group A Divisions and Groups C or D, 2 h between Group B and almost everything, 3 h between Group D or E and F-1. Two notes change the answer often enough to check every time:

A building of not more than 3 storeys with not more than two dwelling units alongside a Group E store needs only 1 h between them (Sentence 3.1.3.1.(2)).
A-2 next to Group C in a building under 3.2.2.51., or A-2 next to Group D under 3.2.2.60., needs 2 h.

Prohibited combinations (OBC Div. B 3.1.3.2.): F-1 may not share a building with Group A, B or C; an F-2 building may contain not more than one residential suite (live/work buildings excepted); buildings under 3.2.2.51. or 3.2.2.60. may not contain a retirement home.

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Combustible, noncombustible and encapsulated mass timber construction

Heavy timber may replace rated combustible construction when no rating over 45 min is required (OBC Div. B 3.1.4.6.); member sizes come from Table 3.1.4.7., with separate rows for roof-only members and members carrying floors.

Noncombustible construction allows the combustible exceptions in 3.1.5.2. to 3.1.5.29. (OBC Div. B 3.1.5.1.). Frequently tested:

Combustible ceiling finishes up to 25 mm thick: flame-spread 25, with up to 10% of each fire compartment's ceiling at 150 (OBC Div. B 3.1.5.12.).
Wood-framed partitions: allowed in unsprinklered fire compartments up to 600 m² if not fire separations, in buildings up to 3 storeys, or in sprinklered floor areas. Never in care, care and treatment, detention or retirement home spaces, and never as exit or vertical service space enclosures (OBC Div. B 3.1.5.16.).
Combustible cladding: building up to 3 storeys or sprinklered, and the wall assembly passes the fire test criteria (flames not more than 5 m above the opening) (OBC Div. B 3.1.5.5.).
A combustible mezzanine in a live/work unit: the lesser of 25% of the unit area or 20 m² (OBC Div. B 3.1.5.27.).

In encapsulated mass timber construction, structural members must meet the minimum sizes of Table 3.1.6.3. (OBC Div. B 3.1.6.3.): 96 mm for floors, roofs and walls exposed on one side, 192 mm for walls exposed on two sides, 192 by 192 mm for beams and columns exposed on 2 or 3 sides, and 224 by 224 mm on 4 sides. Deemed-to-comply layers (OBC Div. B 3.1.6.6.):

Protection	Deemed encapsulation rating
38 mm concrete or gypsum-concrete topping (top side)	50 min
1 layer 12.7 mm Type X gypsum board	25 min
2 layers 12.7 mm Type X	50 min
2 layers 15.9 mm Type X	70 min
3 layers 12.7 mm Type X	80 min

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Fire-resistance ratings and supporting construction

Ratings come from tests or SB-2. Floors, roofs and ceilings are rated from below, firewalls and interior vertical separations from each side, and exterior walls from inside (OBC Div. B 3.1.7.3.). Loadbearing walls, columns and arches in the storey below a rated floor or roof need at least the same rating, except where they support only a service room or service space (OBC Div. B 3.1.7.5.).

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Fire separations and closures

A required fire separation must be continuous, and openings need closures (OBC Div. B 3.1.8.1.). Closure ratings come from Table 3.1.8.4.: the closure rating is usually lower than the wall rating. Key pairs:

Fire separation	Closure
45 min or 1 h	45 min
2 h	1.5 h
3 h	2 h

A 20 min door is allowed between a public corridor and a suite, a corridor and sleeping rooms, or a corridor and classrooms or offices in A-2, where the separation needs not more than 1 h, and in buildings up to 3 storeys where it needs not more than 45 min (OBC Div. B 3.1.8.12.).

Opening size is capped at 11 m² with no side over 3.7 m if either side is unsprinklered, or 22 m² and 6 m if both sides are sprinklered (OBC Div. B 3.1.8.6.). Hold-open devices must release on the right signal and are never allowed on an exit stair door in a building over 3 storeys (OBC Div. B 3.1.8.14.).

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Penetrations, firewalls and fire blocks

Penetrations are sealed by a firestop with an F rating at least equal to the separation's rating, or cast in place where the penetrating item is steel, ferrous, copper, concrete or masonry (OBC Div. B 3.1.9.1.). Firewalls need the stricter FT rating. Small noncombustible outlet boxes (up to 0.016 m² each, 0.065 m² per 9.3 m², 3 mm gap) may skip the firestop (OBC Div. B 3.1.9.3.).

Firewalls are 4 h where they serve Group E or F-1/F-2 floor areas (upper portions serving other occupancies may drop to 2 h) and 2 h otherwise, built of masonry or concrete unless the 2 h alternative applies (OBC Div. B 3.1.10.2.). Parapets are 150 mm for 2 h and 900 mm for 4 h firewalls, not needed where adjoining roofs differ by more than 3 m (OBC Div. B 3.1.10.4.). Openings total not more than 25% of the firewall length per storey (OBC Div. B 3.1.10.5.).

Fire blocks cut concealed wall spaces at each floor and at 20 m horizontally and 3 m vertically (OBC Div. B 3.1.11.2.). Unsprinklered horizontal concealed spaces in combustible floors and roofs are limited to 600 m² and 60 m (flame-spread 25 or less) or 300 m² and 20 m (over 25) (OBC Div. B 3.1.11.5.).

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Flame spread, finishes and roofs

The general limit for wall and ceiling finishes is 150 (OBC Div. B 3.1.13.2.), tightened by Table 3.1.13.2.: 25 in exits, vertical service spaces and certain lobbies, and 75 in unsprinklered A-1 and Group B spaces. Doors may be up to 200 (not in A-1), and residential suite bathrooms up to 200 (OBC Div. B 3.1.13.3.). Public corridors, classroom corridors and similar get 75 on walls (or 25 upper, 150 lower) and 25 on ceilings, all relaxed to 150 when sprinklered (OBC Div. B 3.1.13.6.). Roof coverings need Class A, B or C, with exemptions such as small A-2 buildings with noncombustible underlay (OBC Div. B 3.1.15.2.).

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Occupant load and other site items

Occupant load is the number of fixed seats, 2 persons per sleeping room in a dwelling unit, or the design number but not less than the table value (OBC Div. B 3.1.17.1.). For a room with several uses, take the value giving the most people. Mezzanines count as part of the floor area. Public pools use a formula based on deep and shallow water area (OBC Div. B 3.1.17.2.).

Clearances to overhead power lines run from 1 m to 3.7 m, with a 1.8 m swing assumed when unknown (OBC Div. B 3.1.20.1.). Glass in guards follows SB-13 (OBC Div. B 3.1.21.1.).

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Common traps

Matching a closure rating to the wall rating. Above 45 min, the closure is rated lower than the separation.
Forgetting firewall penetrations need FT, not just F.
Using the 600 m² fire block compartment when exposed materials exceed flame-spread 25.
Applying the 75 corridor limit in a sprinklered floor area, where 150 applies.

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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
Classification and multiple occupancies	Every building or part is classified by major occupancy under, and a building with several major occupancies is classified by all of them.
Combustible, noncombustible and encapsulated mass timber construction	Heavy timber may replace rated combustible construction when no rating over 45 min is required; member sizes come from, with separate rows for roof-only members and members…
Fire-resistance ratings and supporting construction	Ratings come from tests or SB-2. Floors, roofs and ceilings are rated from below, firewalls and interior vertical separations from each side, and exterior walls from inside.
Fire separations and closures	A required fire separation must be continuous, and openings need closures.
Penetrations, firewalls and fire blocks	Penetrations are sealed by a firestop with an F rating at least equal to the separation's rating, or cast in place where the penetrating item is steel, ferrous, copper, concrete…
Flame spread, finishes and roofs	The general limit for wall and ceiling finishes is 150, tightened by: 25 in exits, vertical service spaces and certain lobbies, and 75 in unsprinklered A-1 and Group B spaces.
Occupant load and other site items	Occupant load is the number of fixed seats, 2 persons per sleeping room in a dwelling unit, or the design number but not less than the table value.

Classification and multiple occupancies
Every building or part is classified by major occupancy under, and a building with several major occupancies is classified by all of them.
Combustible, noncombustible and encapsulated mass timber construction
Heavy timber may replace rated combustible construction when no rating over 45 min is required; member sizes come from, with separate rows for roof-only members and members…
Fire-resistance ratings and supporting construction
Ratings come from tests or SB-2. Floors, roofs and ceilings are rated from below, firewalls and interior vertical separations from each side, and exterior walls from inside.
Fire separations and closures
A required fire separation must be continuous, and openings need closures.
Penetrations, firewalls and fire blocks
Penetrations are sealed by a firestop with an F rating at least equal to the separation's rating, or cast in place where the penetrating item is steel, ferrous, copper, concrete…
Flame spread, finishes and roofs
The general limit for wall and ceiling finishes is 150, tightened by: 25 in exits, vertical service spaces and certain lobbies, and 75 in unsprinklered A-1 and Group B spaces.
Occupant load and other site items
Occupant load is the number of fixed seats, 2 persons per sleeping room in a dwelling unit, or the design number but not less than the table value.

Usual exam traps

Matching a closure rating to the wall rating. Above 45 min, the closure is rated lower than the separation.
Forgetting firewall penetrations need FT, not just F.
Using the 600 m² fire block compartment when exposed materials exceed flame-spread 25.
Applying the 75 corridor limit in a sprinklered floor area, where 150 applies.

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Questions on Classification, construction types and fire-resistance (3.1), 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. B Table 3.1.2.1. Major Occupancy Classification
Table 3.1.2.1. Major Occupancy Classification Forming Part of Sentences 3.1.2.1.(1), 3.1.2.2.(1) and 3.11.2.1.(3) Group | Division | Description of Major Occupancy A | 1 | Assembly occupancies intended for the production and viewing of the performing arts A | 2 | Assembly occupancies not elsewhere classified in Group A A | 3 | Assembly occupancies of the arena type A | 4 | Assembly occupancies in which occupants are gathered in the open air B | 1 | Detention occupancies B | 2 | Care and treatment occupancies B | 3 | Care occupancies C | N/A | Residential occupancies D | N/A | Business and personal services occupancies E | N/A | Mercantile occupancies F | 1 | High-hazard industrial occupancies F | 2 | Medium-hazard industrial occupancies F | 3 | Low-hazard industrial occupancies
Open OBC Div. B Table 3.1.2.1. in the code viewer
OBC Div. B 3.1.2.1. Classification of Buildings
(1)Except as permitted by Articles 3.1.2.3. to 3.1.2.7., every building or part thereof shall be classified according to its major occupancy as belonging to one of the Groups or Divisions described in Table 3.1.2.1. (See Note A-3.1.2.1.(1))
(2)A building intended for use by more than one major occupancy shall be classified according to all major occupancies for which it is used or intended to be used.
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OBC Div. B 3.1.2.2. Occupancies of the Same Classification
(1)Any building is deemed to be occupied by a single major occupancy, notwithstanding its use for more than one major occupancy, provided that all occupancies are classified as belonging to the same Group classification or, where the Group is divided into Divisions, as belonging to the same Division classification described in Table 3.1.2.1.
Open OBC Div. B 3.1.2.2. in the code viewer
OBC Div. B 3.1.2.3. Arena-Type Buildings
(1)An arena-type building intended for occasional use for trade shows and similar exhibition purposes shall be classified as Group A, Division 3 occupancy.
Open OBC Div. B 3.1.2.3. in the code viewer
OBC Div. B 3.1.2.4. Police Stations
(1)A police station with detention quarters is permitted to be classified as a Group B, Division 2 major occupancy provided the station is not more than 1 storey in building height and 600 m² in building area.
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OBC Div. B 3.1.2.5. Group B, Division 3 Occupancies
(1)Group B, Division 3 occupancies are permitted to be classified as Group C major occupancies within the application of Part 3 provided
(a)the occupants live as a single housekeeping unit in a suite with sleeping accommodation for not more than 10 persons, and
(b)not more than two occupants require assistance in evacuation in case of an emergency.
Open OBC Div. B 3.1.2.5. in the code viewer
OBC Div. B 3.1.2.6. Storage of Combustible Fibres
(1)Buildings or parts of thereof used for the storage of baled combustible fibres shall be classified as medium-hazard industrial occupancies.
Open OBC Div. B 3.1.2.6. in the code viewer
OBC Div. B 3.1.2.7. Restaurants
(1)A restaurant is permitted to be classified as a Group E major occupancy within the application of Part 3 provided the restaurant is designed to accommodate not more than 30 persons consuming food or drink.
Open OBC Div. B 3.1.2.7. in the code viewer

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OBC Div. B Table 3.1.3.1. Major Occupancy Fire Separations—Minimum Fire-Resistance Rating of Fire Separation, h[1]
Table 3.1.3.1. Major Occupancy Fire Separations—Minimum Fire-Resistance Rating of Fire Separation, h[1] Forming Part of Sentence 3.1.3.1.(1) Major Occupancy | Adjoining Major Occupancy A-1 | Adjoining Major Occupancy A-2 | Adjoining Major Occupancy A-3 | Adjoining Major Occupancy A-4 | Adjoining Major Occupancy B-1 | Adjoining Major Occupancy B-2 | Adjoining Major Occupancy B-3 | Adjoining Major Occupancy C | Adjoining Major Occupancy D | Adjoining Major Occupancy E | Adjoining Major Occupancy F-1 | Adjoining Major Occupancy F-2 | Adjoining Major Occupancy F-3 A-1 | N/A | 1 | 1 | 1 | 2 | 2 | 2 | 1 | 1 | 2 | [2] | 2 | 1 A-2 | 1 | N/A | 1 | 1 | 2 | 2 | 2 | 1[3] | 1[4] | 2 | [2] | 2 | 1 A-3 | 1 | 1 | N/A | 1 | 2 | 2 | 2 | 1 | 1 | 2 | [2] | 2 | 1 A-4 | 1 | 1 | 1 | N/A | 2 | 2 | 2 | 1 | 1 | 2 | [2] | 2 | 1 B-1 | 2 | 2 | 2 | 2 | N/A | 2 | 2 | 2 | 2 | 2 | [2] | 2 | 2 B-2 | 2 | 2 | 2 | 2 | 2 | N/A | 1 | 2 | 2 | 2 | [2] | 2 | 2 B-3 | 2 | 2 | 2 | 2 | 2 | 1 | N/A | 2 | 2 | 2 | [2] | 2 | 2 C | 1 | 1[3] | 1 | 1 | 2 | 2 | 2 | N/A | 1 | 2[5] | [2] | 2[6] | 1 D | 1 | 1[4] | 1 | 1 | 2 | 2 | 2 | 1 | N/A | N/A | 3 | N/A | N/A E | 2 | 2 | 2 | 2 | 2 | 2 | 2 | 2[5] | N/A | N/A | 3 | N/A | N/A F-1 | [2] | [2] | [2] | [2] | [2] | [2] | [2] | [2] | 3 | 3 | N/A | 2 | 2 F-2 | 2 | 2 | 2 | 2 | 2 | 2 | 2 | 2[6] | N/A | N/A | 2 | N/A | N/A F-3 | 1 | 1 | 1 | 1 | 2 | 2 | 2 | 1 | N/A | N/A | 2 | N/A | N/A Notes to Table 3.1.3.1.: (1) Section 3.3. contains requirements for the separation of occupancies and tenancies that are in addition to the requirements for the separation of major occupancies. (2) See Sentence 3.1.3.2.(1). (3) Where the building or part thereof is constructed in accordance with Article 3.2.2.51., a fire separation with a 2 h fire-resistance rating is required between the Group C and Group A, Division 2 major occupancies. (4) Where the building or part thereof is constructed in accordance with Article 3.2.2.60., a fire separation with a 2 h fire-resistance rating is required between the Group D and Group A, Division 2 major occupancies. (5) See Sentence 3.1.3.1.(2). (6) See Sentence 3.1.3.2.(2).
Open OBC Div. B Table 3.1.3.1. in the code viewer
OBC Div. B 3.1.3.1. Separation of Major Occupancies
(1)Except as permitted by Sentences (2) and (3), major occupancies shall be separated from adjoining major occupancies by fire separations having fire-resistance ratings conforming to Table 3.1.3.1.
(2)In a building not more than 3 storeys in building height, if not more than two dwelling units are contained together with a Group E major occupancy, the fire-resistance rating of the fire separation between the two major occupancies need not be more than 1 h.
(3)In a building conforming to the requirements of Articles 3.2.8.2. to 3.2.8.8., the requirements of Sentence (1) for fire separations between major occupancies do not apply at the vertical plane around the perimeter of an opening through the horizontal fire separation.
Open OBC Div. B 3.1.3.1. in the code viewer
OBC Div. B 3.1.3.2. Prohibition of Occupancy Combinations
(1)No major occupancy of Group F, Division 1 shall be contained within a building with any occupancy classified as Group A, B or C.
(2)Except as provided in Sentence (4) and Sentence 3.10.2.4.(9), not more than one suite of residential occupancy shall be contained within a building classified as a Group F, Division 2 major occupancy.
(3)A sleeping room or sleeping area shall not open directly into a room or area where food is intended to be stored, prepared, processed, distributed, served, sold or offered for sale. (See Note A-3.1.3.2.(3))
(4)A Group F, Division 2 major occupancy is permitted in a building containing only live/work units if the occupancy is for the exclusive use of the occupants of the live/work units.
(5)A building within the scope of Article 3.2.2.51. or 3.2.2.60. shall not contain a retirement home.
Open OBC Div. B 3.1.3.2. in the code viewer
OBC Div. B 3.1.4.6. Heavy Timber Construction Alternative
(1)If combustible construction is permitted and is not required to have a fire-resistance rating more than 45 min, heavy timber construction is permitted to be used.
(2)If heavy timber construction is permitted, it shall conform to Article 3.1.4.7.
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OBC Div. B Table 3.1.4.7. Heavy Timber Dimensions
Table 3.1.4.7. Heavy Timber Dimensions Forming Part of Sentence 3.1.4.7.(2) Supported Assembly | Structural Element | Solid Sawn (width × depth), mm × mm | Glued-Laminated (width × depth), mm × mm | Round (diam), mm Roofs only | Columns | 140×191 | 130×190 | 180 Roofs only | Arches supported on the tops of walls or abutments | 89×140 | 80×152 | N/A Roofs only | Beams, girders and trusses | 89×140 | 80×152 | N/A Roofs only | Arches supported at or near the floor line | 140×140 | 130×152 | N/A Floors, floors plus roofs | Columns | 191×191 | 175×190 | 200 Floors, floors plus roofs | Beams, girders, trusses and arches | 140×241 or 191×191 | 130×228 or 175×190 | N/A
Open OBC Div. B Table 3.1.4.7. in the code viewer
OBC Div. B 3.1.5.1. Noncombustible Materials)
(1)Except as permitted by Sentences (2) to (4) and Articles 3.1.5.2. to 3.1.5.29., 3.1.13.4. and 3.2.2.16., a building or part of a building required to be of noncombustible construction, shall be constructed with noncombustible materials. (See also Subsection 3.1.13. for the requirements regarding the flame-spread rating of interior finishes.)
(2)Notwithstanding the definition of noncombustible materials stated in Article 1.4.1.2. of Division A, a material is permitted to be used in noncombustible construction provided that, when tested in accordance with ULC S135, "Standard Test Method for the Determination of Combustibility Parameters of Building Materials Using an Oxygen Consumption Calorimeter (Cone Calorimeter)", at a heat flux of 50 kW/m²,
(a)its average total heat release is not more than 3 MJ/m²,
(b)its average total smoke extinction area is not more than 1.0 m², and
(c)the test duration is extended beyond the time stipulated in the referenced standard until it is clear that there is no further release of heat or smoke.
(3)If a material referred to in Sentence (2) consists of a number of discrete layers and testing reveals that the surface layer or layers protect the underlying layers such that complete combustion of the underlying layers does not occur, the test shall be repeated by removing the outer layers sequentially until all layers have been exposed during testing, or until complete combustion has occurred.
(4)The acceptance criteria for a material tested in accordance with Sentence (3) shall be based on the cumulative emissions from all layers, which must not exceed the criteria stated in Clauses (2)(a) and (b).
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OBC Div. B 3.1.5.12. Combustible Interior Finishes
(1)Except permitted in Sentences (2) and (3), combustible interior wall and ceiling finishes referred to in Clause 3.1.13.1.(2)(b) that are not more than 1 mm thick are permitted in a building required to be of noncombustible construction.
(2)Combustible interior wall finishes, other than foamed plastics, that are not more than 25 mm thick are permitted in a building required to be of noncombustible construction, provided they have a flame-spread rating not more than 150 on any exposed surface or any surface that would be exposed by cutting through the material in any direction.
(3)Except as provided in Sentence (4), combustible interior ceiling finishes, other than foamed plastics, that are not more than 25 mm thick are permitted in a building required to be of noncombustible construction, provided they have a flame-spread rating not more than 25 on any exposed surface or on any surface that would be exposed by cutting through the material in any direction, except that not more than 10% of the ceiling area within each fire compartment is permitted to have a flame-spread rating not more than 150.
(4)Combustible interior ceiling finishes made of fire-retardant-treated wood are permitted in a building required to be of noncombustible construction, provided they are not more than 25 mm thick or are exposed fire-retardant-treated wood battens.
Open OBC Div. B 3.1.5.12. in the code viewer
OBC Div. B 3.1.5.16. Combustible Elements in Partitions
(1)Except as permitted by Sentence (2), solid lumber partitions not less than 38 mm thick and wood framing in partitions located in a fire compartment not more than 600 m² in area are permitted to be used in a building required to be of noncombustible construction in a floor area that is not sprinklered provided the partitions
(a)are not required fire separations, and
(b)are not located in a care, care and treatment or detention occupancy or in a retirement home.
(2)Partitions installed in a building of noncombustible construction are permitted to contain wood framing provided
(a)the building is not more than 3 storeys in building height,
(b)the partitions are not located in a care, care and treatment or detention occupancy or in a retirement home, and
(c)the partitions are not installed as enclosures for exits or vertical service spaces.
(3)Solid lumber partitions not less than 38 mm thick and partitions that contain wood framing are permitted to be used in a building required to be of noncombustible construction provided
(a)the floor area containing the partitions is sprinklered throughout, and
(b)the partitions are not
(i)located in a care, care and treatment or detention occupancy or in a retirement home,
(ii)installed as enclosures for exits or vertical service spaces, or
(iii)used to satisfy the requirements of Clause 3.2.8.1.(1)(a).
Open OBC Div. B 3.1.5.16. in the code viewer
OBC Div. B 3.1.5.5. Combustible Cladding on Exterior Walls
(1)Except as provided in Sentences (2) and (3), combustible cladding is permitted to be used on an exterior wall assembly in a building required to be of noncombustible construction, provided
(a)the building is
(i)not more than 3 storeys in building height, or
(ii)sprinklered throughout, and
(b)except as provided in Sentence (4), when tested in accordance with CAN/ULC-S134, "Standard Method of Fire Test of Exterior Wall Assemblies," the wall assembly satisfies the following criteria for testing and conditions of acceptance: (See Note A-3.1.5.5.(1)(b))
(i)flaming on or in the wall assembly does not spread more than 5 m above the opening, and (See Note A-3.1.5.5.(1)(b)(i))
(ii)the heat flux during the flame exposure on the wall assembly is not more than 35 kW/m² measured at 3.5 mabove the opening. (See Note A-3.1.5.5.(1)(b)(ii))
(2)Except as permitted by Articles 3.2.3.10. and 3.2.3.11., where the limiting distance in Tables 3.2.3.1.-B to 3.2.3.1.-E permits an area of unprotected openings of not more than 10% of the exposing building face, the construction requirements of Table 3.2.3.7. shall be met.
(3)A wall assembly permitted by Sentence (1) that includes combustible cladding of fire-retardant-treated wood shall be tested for fire exposure after the cladding has been subjected to an accelerated weathering test as specified in ASTM D2898, "Standard Practice for Accelerated Weathering of Fire-Retardant-Treated Wood for Fire Testing."
(4)Exterior wall assemblies constructed in accordance with Section 6 of MMAH Supplementary Standard SB-2, "Fire Performance Ratings" are deemed to comply with Clause (1)(b).
Open OBC Div. B 3.1.5.5. in the code viewer
OBC Div. B 3.1.5.27. Combustible Mezzanines
(1)In a building required to be of noncombustible construction, a mezzanine located within a live/work unit is permitted to be of combustible construction, provided the area of the mezzanine is not more than 25% of the floor area of the live/work unit or 20 m², whichever is less, and has no obstructions more than 1,070 mm above the floor.
Open OBC Div. B 3.1.5.27. in the code viewer
OBC Div. B Table 3.1.6.3. Minimum Dimensions of Structural Mass Timber Elements in Encapsulated Mass Timber Construction
Table 3.1.6.3. — Minimum Dimensions of Structural Mass Timber Elements in Encapsulated Mass Timber Construction Forming Part of Sentences 3.1.6.3.(2), 3.1.6.8.(1) and 3.1.6.17.(1) Structural Wood Elements | Minimum Thickness, mm | Minimum Width x Depth, mm x mm Walls that are fire separations or exterior walls (1-sided fire exposure) | 96 | N/A Walls that require a fire-resistance rating, but are not fire separations (2-sided fire exposure) | 192 | N/A Floors[1] and roofs (1-sided fire exposure) | 96 | N/A Beams, columns and arches (2- or 3-sided fire exposure) | N/A | 192 x 192 Beams, columns and arches (4-sided fire exposure) | N/A | 224 x 224 Notes to Table 3.1.6.3.: (1) The minimum dimensions for floor assemblies are also applicable to mezzanines and exterior balconies.
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OBC Div. B 3.1.6.3. Structural Mass Timber Elements
(1)Except as otherwise provided in this Subsection and Articles 3.2.2.16. and 3.2.3.19., a building or part of a building permitted to be of encapsulated mass timber construction is permitted to include structural mass timber elements, including beams, columns, arches and wall, floor and roof assemblies, provided they comply with Sentences (2) and (3).
(2)Structural mass timber elements referred to in Sentence (1) shall
(a)except as provided in Sentence (4), be arranged in heavy solid masses containing no concealed spaces,
(b)have essentially smooth flat surfaces with no thin sections or sharp projections, and
(c)except as provided in Sentence 3.1.6.17.(1), conform to the minimum dimensions stated in Table 3.1.6.3.
(3)Adhesives used in structural mass timber elements referred to in Sentence (1) that are constructed of cross-laminated timber shall conform to the elevated temperature performance requirements in ANSI/APA PRG 320, "Standard for Performance-Rated Cross-Laminated Timber."
(4)Concealed spaces are permitted within structural mass timber elements referred to in Sentence (2) and need not conform to Sentence 3.1.6.4.(1) provided the concealed spaces are,
(a)sprinklered and divided into compartments by fire blocks in conformance with Subsection 3.1.11.,
(b)completely filled with rock or slag fibre insulation conforming to CAN/ULC-S702.1 "Standard for Mineral Fibre Thermal Insulation for Buildings, Part 1: Material Specification," and having a density not less than 32 kg/m²,
(c)if horizontal, lined with not less than a single layer of 12.7 mm thick Type X gypsum board or noncombustible material providing an encapsulation rating of not less than 25 min, or
(d)if vertical, lined with not less than a single layer of 12.7 mm thick Type X gypsum board or noncombustible material providing an encapsulation rating of not less than 25 min and vertically divided into compartments by fire blocks in conformance with Subsection 3.1.11.
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OBC Div. B 3.1.6.6. Encapsulation Materials
(1)Gypsum-concrete topping and concrete not less than 38 mm thick are deemed to have an encapsulation rating of 50 min when installed on the upper side of a mass timber floor or roof assembly.
(2)One layer of Type X gypsum board conforming to ASTM C1396/C1396 m, "Standard Specification for Gypsum Board," or CAN/CSA-A82.27-M, "Gypsum Board," not less than 12.7 mm thick, are deemed to have an encapsulation rating of 25 min when installed on a mass timber element in accordance with Sentence (6).
(3)Two layers of Type X gypsum board conforming to ASTM C1396/C1396 m, "Standard Specification for Gypsum Board," or CAN/CSA-A82.27-M, "Gypsum Board," each not less than 12.7 mm thick, are deemed to have an encapsulation rating of 50 min when installed on a mass timber element in accordance with Sentence (6).
(4)Two layers of Type X gypsum board conforming to ASTM C1396/C1396 m, "Standard Specification for Gypsum Board," or CAN/CSA-A82.27-M, "Gypsum Board," each not less than 15.9 mm thick, are deemed to have an encapsulation rating of 70 min when installed on a mass timber element in accordance with Sentence (6).
(5)Three layers of Type X gypsum board conforming to ASTM C1396/C1396 m, "Standard Specification for Gypsum Board," or CAN/CSA-A82.27-M, "Gypsum Board," each not less than 12.7 mm thick, are deemed to have an encapsulation rating of 80 min when installed on a mass timber element in accordance with Sentence (6).
(6)The gypsum board described in Sentences (2) to (5) shall be
(a)fastened with a minimum of two rows of screws in each layer
(i)directly to the mass timber element with screws of sufficient length to penetrate not less than 20 mm into the mass timber element that are spaced not more than 400 mm o.c. and 20 mm to 38 mm from the boards' edges, or
(ii)to wood furring or resilient metal or steel furring channels not more than 25 mm thick spaced not more than 400 mm o.c. on the mass timber element,
(b)for multiple layer systems, installed with the joints in each layer staggered from those in the adjacent layer, and
(c)installed in conformance with ASTM C840, "Standard Specification for Application and Finishing of Gypsum Board," except that, for multiple layer systems, their joints need not be taped and finished. (See Note A-3.1.6.6.(6))
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OBC Div. B 3.1.7.3. Exposure Conditions for Rating
(1)Floor, roof and ceiling assemblies shall be rated for exposure to fire on the underside.
(2)Firewalls and interior vertical fire separations shall be rated for exposure to fire on each side.
(3)Exterior walls shall be rated for exposure to fire from inside the building.
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OBC Div. B 3.1.7.5. Rating of Supporting Construction
(1)Except as permitted by Sentence (2) and by Articles 3.2.2.20. to 3.2.2.93. for mixed types of construction, all loadbearing walls, columns and arches in the storey immediately below a floor or roof assembly required to have a fire-resistance rating shall have a fire-resistance rating not less than that required for the supported floor or roof assembly.
(2)Loadbearing walls, columns and arches supporting a service room or service space need not conform to Sentence (1).
(3)Except as provided in Sentence (4) and except for noncombustible roof assemblies required by Clauses 3.2.2.51.(2)(c) and 3.2.2.60.(2)(c), if an assembly is required to be of noncombustible construction and have a fire-resistance rating, it shall be supported by noncombustible construction.
(4)Except for portions of a building constructed in accordance with Article 3.2.2.7. that are required to be of noncombustible construction, assemblies of noncombustible construction in buildings or portions of buildings permitted to be of encapsulated mass timber construction are permitted to be supported by encapsulated mass timber construction.
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OBC Div. B 3.1.8.1. General Requirements
(1)Any wall, partition or floor assembly required to be a fire separation shall
(a)except as permitted by Sentence (2), be constructed as a continuous element in conformance with Article 3.1.8.3., and
(b)as required in this Part, have a fire-resistance rating as specified. (See Note A-3.1.8.1.(1)(b))
(2)Openings in a fire separation shall be protected with closures, shafts or other means in conformance with Articles 3.1.8.4. to 3.1.8.20. and Subsections 3.1.9. and 3.2.8. (See Note A-3.1.8.1.(2))
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OBC Div. B Table 3.1.8.4. Fire-Protection Rating of Closures
Table 3.1.8.4. — Fire-Protection Rating of Closures Forming Part of Sentence 3.1.8.4.(2) Fire Separation | Closure 30 min | 20 min 45 min | 45 min 1 h | 45 min 1.5 h | 1 h 2 h | 1.5 h 3 h | 2 h 4 h | 3 h
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OBC Div. B 3.1.8.12. Twenty-Minute Closures
(1)A door assembly having a fire-protection rating not less than 20 min is permitted to be used as a closure in
(a)a fire separation not required to have a fire-resistance rating more than 1 h, located between
(i)a public corridor and a suite,
(ii)a corridor and adjacent sleeping rooms, or
(iii)a corridor and adjacent classrooms, offices and libraries in Group A, Division 2 major occupancies, or
(b)a fire separation not required to have a fire-resistance rating more than 45 min, located in a building not more than 3 storeys in building height.
(2)The requirements for noncombustible sills and combustible floor coverings in NFPA 80, "Standard for Fire Doors and Other Opening Protectives," do not apply to a door described in Sentence (1).
(3)A door described in Sentence (1) shall have clearances of not more than 6 mm at the bottom and not more than 3 mm at the sides and top.
(4)In elementary and secondary schools, a door assembly conforming to Articles 9.10.13.2. and 9.10.13.3. is permitted to be used as a closure in a fire separation having a fire-resistance rating of 30 min.
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OBC Div. B 3.1.8.6. Maximum Openings
(1)The size of an opening in an interior fire separation required to be protected with a closure shall be not more than 11 m², with no dimension more than 3.7 m, if a fire compartment on either side of the fire separation is not sprinklered.
(2)The size of an opening in an interior fire separation required to be protected with a closure shall be not more than 22 m², with no dimension more than 6 m, provided the fire compartments on both sides of the fire separation are sprinklered.
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OBC Div. B 3.1.8.14. Hold-Open Devices
(1)Except as provided in Sentences 3.1.8.10.(2) and 3.1.8.11.(3), a hold-open device is permitted to be used on a closure in a required fire separation, other than on an exit stair door in a building more than 3 storeys in building height and on a door for a vestibule required by Article 3.3.5.7., provided the device is designed to release the closure in conformance with this Article.
(2)Except as provided in Sentences (5) and (6), where the building is provided with a fire alarm system, a hold-open device permitted by Sentence (1) shall release
(a)in a single-stage system, upon any signal from the fire alarm system, and
(b)in a 2-stage system,
(i)upon any alert signal from the fire alarm system, or
(ii)upon actuation of any adjacent smoke detectors.
(3)Where the building is provided with a fire alarm system, a hold-open device permitted by Sentence (1) shall release upon a signal from a smoke detector connected to the fire alarm system and located as described in CAN/ULC-S524, "Standard for Installation of Fire Alarm Systems," where the hold-open device is used on
(a)an exit door,
(b)a door opening into a public corridor,
(c)an egress door referred to in Sentence 3.4.2.4.(2),
(d)a closure serving an assembly, care, care and treatment, detention, or residential occupancy,
(e)a door in a fire separation referred to in Clause 3.3.1.7.(1)(b) or Sentence 3.3.3.5.(4) or 3.3.4.11.(4), or
(f)a door required to function as part of a smoke control system.
(4)Where the building is not provided with a fire alarm system, a hold-open device permitted by Sentence (1) shall release upon a signal from a smoke alarm located on either side of the fire separation at ceiling level within 1.5 m horizontally of the closure opening in the fire separation, where the hold-open device is used on closures described in Clauses (3)(a) to (e).
(5)Where a hold-open device is used on closures other than those described in Sentences (3) and (4), it is permitted to be released upon actuation of a heat-actuated device.
(6)A hold-open device used on a door located between a corridor used by the public and an adjacent sleeping room in a care and treatment occupancy need not release automatically as stated in Sentence (2).
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OBC Div. B 3.1.9.1. Firestops
(1)Except as provided in Sentences (2) to (7) and Article 3.1.9.3., penetrations of a fire separation or a membrane forming part of an assembly required to have a fire-resistance rating shall be
(a)sealed by a firestop that, when subjected to the fire test method in CAN/ULC-S115, "Standard Method of Fire Tests of Firestop Systems," has an F rating not less than the required fire-resistance rating of the fire separation, or
(b)cast-in-place, where the item penetrating the fire separation is steel, ferrous, copper, concrete or masonry. (See Note A-3.1.9.1.(1)(b))
(See also Article 3.1.9.4. for requirements regarding penetrations by combustible drain, waste and vent piping.)
(2)Except as permitted in Sentence (6), penetrations of a firewall or a horizontal fire separation that is required to have a fire-resistance rating in conformance with Article 3.2.1.2. shall be sealed at the penetration by a firestop that, when subjected to the fire test method in CAN/ULC-S115, "Standard Method of Fire Tests of Firestop Systems," has an FT rating not less than the fire-resistance rating for the fire separation.
(3)Except as permitted in Sentences (6) and (7), penetrations of a fire separation in conformance with Sentence 3.6.4.2.(2) shall be sealed by a firestop that, when subjected to the fire test method in CAN/ULC-S115, "Standard Method of Fire Tests of Firestop Systems," has an FT rating not less than the fire-resistance rating for the fire separation of the assembly.
(4)Sprinklers are permitted to penetrate a fire separation or a membrane forming part of an assembly required to have a fire-resistance rating without having to meet the firestop requirements of Sentences (1) to (3), provided the annular space created by the penetration of a fire sprinkler is covered by a metal escutcheon plate in accordance with NFPA 13, "Standard for the Installation of Sprinkler Systems."
(5)Unless specifically designed with a firestop, fire dampers are permitted to penetrate a fire separation or a membrane forming part of an assembly required to have a fire-resistance rating without having to meet the firestop requirements of Sentences (1) to (3), provided the fire damper is installed in conformance with NFPA 80, "Standard for Fire Doors and Other Opening Protectives."
(6)Service equipment penetrations through a horizontal fire separation having a fire-resistance rating as described in Sentences (2) and (3) that are contained within the cavity of a wall above and below the horizontal fire separation are permitted to be sealed at the penetration by a firestop that, when subjected to the fire test method in CAN/ULC-S115, "Standard Method of Fire Tests of Firestop Systems," has an F rating not less than the fire-resistance rating for the fire separation.
(7)Service equipment penetrations through a horizontal fire separation having a fire-resistance rating as described in Sentence (3) are permitted to be sealed at the penetration by a firestop that, when subjected to the fire test method in CAN/ULC-S115, "Standard Method of Fire Tests of Firestop Systems," has an F rating not less than the fire-resistance rating for the fire separation, provided the penetration
(a)is contained within the concealed space of a floor or ceiling assembly having a fire-resistance rating,
(b)is located above a ceiling membrane that is a horizontal fire separation, or
(c)is contained within a horizontal service space conforming to Subsection 3.6.4. that is directly above or below the floor.
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OBC Div. B 3.1.9.3. Penetration by Outlet Boxes (See also Note A-3.1.9.2.(1))
(1)Except as provided in Sentence (3), outlet boxes are permitted to penetrate the membrane of an assembly required to have a fire-resistance rating, provided they are sealed at the penetration by a firestop that has an FT rating not less than the fire-resistance rating of the fire separation when subjected to the fire test method in CAN/ULC-S115, "Standard Method of Fire Tests of Firestop Systems."
(2)Combustible outlet boxes are permitted to penetrate the membrane of an assembly required to have a fire-resistance rating, provided they are sealed at the penetration by a firestop that, when subjected to the fire test method in CAN/ULC-S115, "Standard Method of Fire Tests of Firestop Systems," has an FT rating not less than the fire-resistance rating for the fire separation.
(3)Except as provided in Sentences 3.1.9.1.(2) and (3), noncombustible outlet boxes that penetrate a vertical fire separation or a membrane forming part of an assembly required to have a fire-resistance rating need not conform to Sentence (1), provided
(a)they do not exceed,
(i)0.016 m² in area, and
(ii)an aggregate area of 0.065 m² in any 9.3 m² of surface area, and
(b)the annular space between the membrane and noncombustible electrical outlet boxes does not exceed 3 mm.
(4)Outlet boxes on opposite sides of a vertical fire separation having a fire-resistance rating shall be separated by
(a)a horizontal distance of not less than 600 mm,
(b)a fire block conforming to Article 3.1.11.7., or
(c)a firestop installed on each outlet box that has an FT rating not less than the fire-resistance rating of the fire separation when subjected to the fire test method in CAN/ULC-S115, "Standard Method of Fire Tests of Firestop Systems."
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OBC Div. B 3.1.10.2. Rating of Firewalls
(1)A firewall that separates a building or buildings with floor areas containing a Group E or a Group F, Division 1 or 2 major occupancy shall be constructed as a fire separation of noncombustible construction having a fire-resistance rating not less than 4 h, except that where the upper portion of a firewall separates floor areas containing other than Group E or Group F, Division 1 or 2 major occupancies, the fire-resistance rating of the upper portion of the firewall is permitted to be not less than 2 h.
(2)A firewall that separates a building or buildings with floor areas containing major occupancies other than Group E or Group F, Division 1 or 2 shall be constructed as a fire separation of noncombustible construction having a fire-resistance rating not less than 2 h.
(3)Except as permitted by Sentence (4), the required fire-resistance rating of a firewall, except for closures, shall be provided by masonry or concrete.
(4)A firewall permitted to have a fire-resistance rating not more than 2 h need not be constructed of masonry or concrete provided
(a)the assembly providing the fire-resistance rating is protected against damage that would compromise the integrity of the assembly,
(b)the design conforms to Article 4.1.5.17.,
(c)the level of performance of the firewall is not less than of masonry or concrete in the areas of
(i)performance during fire conditions,
(ii)mechanical damage during the normal use of the building, and
(iii)resistance to damage from moisture,
(d)the firewall separates buildings or buildings with floor areas that do not contain
(i)a Group B, Division 1 major occupancy, or
(ii)a Group B, Division 2 major occupancy, and
(e)the firewall does not separate a building regulated by the provisions of Subsection 3.2.6. or a building within the scope of Article 3.2.2.51. or 3.2.2.60. from another building unless the buildings on both sides of the firewall are sprinklered. (See Note A-3.1.10.2.(4))
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OBC Div. B 3.1.10.4. Parapets
(1)Except as permitted by Sentences (2) and 3.1.10.3.(2), a firewall shall extend above the roof surface to form a parapet not less than
(a)150 mm high for a firewall required to have a fire-resistance rating not less than 2 h, and
(b)900 mm high for a firewall required to have a fire-resistance rating not less than 4 h.
(2)A firewall that separates 2 buildings with roofs at different elevations need not extend above the upper roof surface to form a parapet, provided the difference in elevation between the roofs is more than 3 m.
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OBC Div. B 3.1.10.5. Maximum Openings
(1)Openings in a firewall shall conform to the size limits described in Article 3.1.8.6.
(2)The aggregate width of openings in a firewall within a storey shall be not more than 25% of the entire length of the firewall.
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OBC Div. B 3.1.11.2. Fire Blocks in Wall Assemblies
(1)Except as permitted by Sentence (2), fire blocks conforming to Article 3.1.11.7. shall be provided to block off concealed spaces within a wall assembly
(a)at every floor level,
(b)at every ceiling level where the ceiling forms part of an assembly required to have a fire-resistance rating, and
(c)so that the maximum horizontal dimension is not more than 20 m and the maximum vertical dimension is not more than 3 m.
(2)Fire blocks conforming to Sentence (1) are not required provided
(a)the wall space is filled with insulation,
(b)the exposed construction materials and any insulation within the wall space are noncombustible,
(c)the exposed materials within the wall space, including insulation but not including wiring, piping or similar services, have a flame-spread rating not more than 25 on any exposed surface, or on any surface that would be exposed by cutting through the material in any direction, and fire blocks are installed so that the vertical distance between them is not more than 10 m, or
(d)the insulated wall assembly contains not more than one concealed air space, and the horizontal thickness of that air space is not more than 25 mm.
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OBC Div. B 3.1.11.5. Fire Blocks in Horizontal Concealed Spaces
(1)Except for crawl spaces conforming to Sentence 3.1.11.6.(1) and as required in Sentence (3), horizontal concealed spaces within a floor assembly or roof assembly of combustible construction, in which sprinklers are not installed, shall be separated by construction conforming to Article 3.1.11.7. into compartments
(a)not more than 600 m² in area with no dimension more than 60 m, if the exposed construction materials within the space have a flame-spread rating not more than 25, and
(b)not more than 300 m² in area with no dimension more than 20 m, if the exposed construction materials within the space have a flame-spread rating more than 25.
(See Note A-3.1.11.5.(1))
(2)A concealed space in an exterior cornice, a mansard style roof, a balcony or a canopy in which exposed construction materials within the space have a flame-spread rating more than 25, shall be separated by construction conforming to Article 3.1.11.7.
(a)at locations where the concealed space extends across the ends of required vertical fire separations, and
(b)so that the maximum dimension in the concealed space is not more than 20 m.
(3)Except as provided by Sentence (5), in buildings or parts thereof conforming to Article 3.2.2.51. or 3.2.2.60., horizontal concealed spaces within a floor assembly or roof assembly of combustible construction shall be separated by construction conforming to Article 3.1.11.7. into compartments that are
(a)not more than 600 m² in area with no dimension more than 60 m, if the exposed construction materials within the space have a flame-spread rating not more than 25, and
(b)not more than 300 m² in area with no dimension more than 20 m, if the exposed construction materials within the space have a flame-spread rating more than 25. (See Note A-3.1.11.5.(3) and (4))
(4)Except for crawl spaces conforming to Sentence 3.1.11.6.(1) and except as provided in Sentence (5), in buildings or parts thereof conforming to Article 3.2.2.48., 3.2.2.57. or 3.2.2.93., horizontal concealed spaces within a floor assembly or roof assembly of encapsulated mass timber construction shall be separated by construction conforming to Article 3.1.11.7. into compartments that are
(a)not more than 600 m² in area with no dimension more than 60 m, if the exposed construction materials within the space have a flame-spread rating not more than 25, and
(b)not more than 300 m² in area with no dimension more than 20 m, if the exposed construction materials within the space have a flame-spread rating more than 25. (See Note A-3.1.11.5.(3) and (4))
(5)Fire blocks conforming to Sentences (3) and (4) are not required where the horizontal concealed space within the floor or roof assembly is entirely filled with noncombustible insulation such that any air gap between the top of the insulation and the floor or roof deck does not exceed 50 mm.
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OBC Div. B 3.1.13.2. Flame-Spread Rating
(1)Except as otherwise required or permitted by this Subsection, the flame-spread rating of interior wall and ceiling finishes, including glazing and skylights, shall be not more than 150 and shall conform to Table 3.1.13.2.
(2)Except as permitted by Sentence (3), doors, other than those in Group A, Division 1 occupancies, need not conform to Sentence (1) provided they have a flame-spread rating not more than 200. (See Note A-3.1.13.2.(2))
(3)Doors within a dwelling unit need not conform to Sentences (1) and (2).
(4)Up to 10% of the total wall area and 10% of the total ceiling area of a wall or ceiling finish that is required by Sentence (1) to have a flame-spread rating less than 150 is permitted to have a flame-spread rating not more than 150, except that up to 25% of the total wall area of lobbies described in Sentence 3.4.4.2.(2) is permitted to have a flame-spread rating not more than 150.
(5)Except in the case of Group A, Division 1 occupancies, combustible doors, skylights, glazing and light diffusers and lenses shall not be considered in the calculation of wall and ceiling areas described in Sentence (4).
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OBC Div. B Table 3.1.13.2. Flame-Spread Ratings
Table 3.1.13.2. Flame-Spread Ratings Forming Part of Sentence 3.1.13.2.(1) Occupancy, Location or Element | Maximum Flame-Spread Rating — Sprinklered Walls and Ceilings | Maximum Flame-Spread Rating — Not Sprinklered Walls and Ceilings Group A, Division 1 occupancies, including doors, skylights, glazing and light diffusers and lenses | 150 | 75 Group B occupancies | 150 | 75 Exits[1] | 25 | 25 Lobbies described in Sentence 3.4.4.2.(2) | 25 | 25 Covered vehicular passageways, except for roof assemblies of heavy timber construction in the passageways | 25 | 25 Vertical service spaces | 25 | 25 Notes to Table 3.1.13.2.: (1) See Articles 3.1.13.8. and 3.1.13.10.
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OBC Div. B 3.1.13.3. Bathrooms in Residential Suites
(1)The flame-spread rating of interior wall and ceiling finishes for a bathroom within a suite of residential occupancy shall be not more than 200.
(2)Plumbing fixtures shall have a flame-spread rating not more than 200.
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OBC Div. B 3.1.13.6. Corridors
(1)Except as permitted by Sentences (2) and (3), the flame-spread rating shall be not more than 75 for the interior wall finish of
(a)a public corridor,
(b)a corridor used by the public in,
(i)an assembly occupancy, or
(ii)a care, care and treatment or detention occupancy,
(c)a corridor serving classrooms, or
(d)a corridor serving sleeping rooms in a care, care and treatment or detention occupancy.
(2)The flame-spread rating for corridors specified in Sentence (1) is permitted to be waived, provided the flame-spread rating is not more than
(a)25 on the upper half of the wall, and
(b)150 on the lower half of the wall.
(3)Where the floor area is sprinklered throughout, the flame-spread ratings for corridors specified in Sentences (1) and (2) shall be not more than 150.
(4)The flame-spread ratings specified in Sentences (1), (2) and (3) apply to occupancies in the corridor as well as to the corridor itself.
(5)Except as provided in Sentence (6), the interior ceiling finish of corridors and occupancies referred to in Sentences (1) and (4) shall have a flame-spread rating not more than 25.
(6)Where the floor area is sprinklered throughout, the flame-spread rating of the interior ceiling finish of corridors and occupancies referred to in Sentences (1) and (4) shall be not more than 150.
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OBC Div. B 3.1.15.2. Roof Coverings
(1)Except as provided by Sentences (2) to (4), every roof covering shall have a Class A, B or C classification as determined in accordance with Article 3.1.15.1.
(2)A roof covering is not required to have a Class A, B or C classification for
(a)a tent,
(b)an air-supported structure,
(c)a building of Group A, Division 2 occupancy not more than 2 storeys in building height and not more than 1,000 m² in building area, provided the roof covering is underlaid with noncombustible material, or
(d)a steel building system described in Article 4.3.4.3., provided the roof covering consists of brick, masonry, concrete, metal sheets or metal shingles.
(3)Except as provided in Sentence (5), roof coverings on buildings conforming to Article 3.2.2.51. or 3.2.2.60. shall have a Class A classification where the roof height is greater than 25 m measured from the floor of the first storey to the highest point of the roof.
(4)Except as provided in Sentence (5), roof coverings in buildings or parts of buildings permitted to be of encapsulated mass timber construction shall have a Class A classification if the roof height is greater than 25 m measured from the floor of the first storey to the highest point of the roof.
(5)Where buildings or parts thereof conforming to Article 3.2.2.48., 3.2.2.51., 3.2.2.57., 3.2.2.60. or 3.2.2.93. include non-contiguous roof assemblies at different elevations, the roof coverings referred to in Sentences (3) and (4) are permitted to be evaluated separately to determine the roof covering classification required.
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OBC Div. B 3.1.17.1. Occupant Load Determination
(1)The occupant load of a floor area or part of a floor area, shall be based on
(a)the number of seats in an assembly occupancy having fixed seats,
(b)2 persons per sleeping room in a dwelling unit, or
(c)the number of persons for which the area is designed, but not less than that determined from Table 3.1.17.1. for occupancies other than those described in Clauses (a) and (b), unless it can be shown that the area will be occupied by fewer persons.
(2)If a floor area or part thereof it has been designed for an occupant load other than that determined from Table 3.1.17.1., a permanent sign indicating that occupant load shall be posted in a conspicuous location.
(3)For the purposes of this Article, mezzanines, tiers and balconies shall be regarded as part of the floor area.
(4)If a room or group of rooms is intended for different occupancies at different times, the value to be used from Table 3.1.17.1. shall be the value that gives the greatest number of persons for the occupancies concerned.
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OBC Div. B 3.1.17.2. Public Pools
(1)The occupant load of a public pool, except a wave action pool, shall be determined by the following formula:
occupant load = D/2.5 + S/1.4
where.
D = the water surface area in square metres of the part of the pool that is deeper than 1,350 mm; and
S = the water surface area in square metres of the part of the pool that is 1,350 mm in depth or less.
(2)The occupant load of a wave action pool shall be determined by the following formula:
occupant load = D/2.5 + S/1.1
where,
D = the water surface area in square metres of the part of the pool where the still water depth is greater than 1,000 mm; and
S = the water surface area in square metres of the part of the pool where the still water depth is 1,000 mm or less
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OBC Div. B 3.1.20.1. Clearance to Buildings
(1)A building shall not be located beneath existing above ground electrical conductors.
(2)The horizontal clearance measured from the maximum conductor swing to the building, including balconies, fire escapes, flat roofs or other accessible projections beyond the face of the building, shall,
(a)be not less than 1 m, for electrical conductors carrying voltages 750 V or less, except where necessary to connect to the electrical wiring of the building,
(b)be not less than 3 m, for electrical conductors carrying voltages greater than 750 V but not exceeding 46 kV,
(c)be not less than 3.7 m, for electrical conductors carrying voltages greater than 46 kV but not exceeding 69 kV, or
(d)conform to the requirements of CAN/CSA-C22.3 No.1, "Overhead Systems," for electrical conductors carrying voltages greater than 69 kV.
(3)Where the swing of an above ground electrical conductor not owned or operated by an electrical supply authority is not known, a swing of not less than 1.8 m shall be used.
(4)Sentences (1) to (3) do not apply to a building containing electrical equipment and electrical installations used exclusively in the generation, transformation or transmission of electrical power or energy intended for sale or distribution to the public.
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OBC Div. B 3.1.21.1. Glass
(1)Except as provided in Sentence 3.3.4.7.(2), glass in guards shall conform to MMAH Supplementary Standard SB-13, "Glass in Guards."
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