Part 3 classification, construction and building size (Small Buildings)

Last updated October 22, 2026

Values this chapter turns on

closure rating in a 1 h fire separation: 45 min; closure rating in a 1 h fire separation
firewall rating for Group E, F-1 or F-2 areas: 4 h; firewall rating for Group E, F-1 or F-2 areas
parapet above the roof for a 4 h firewall: 900 mm; parapet above the roof for a 4 h firewall
area per person for office occupant load: 9.30 m²; area per person for office occupant load

The Small Buildings syllabus pulls in a list of Part 3 articles: noncombustible materials, closures and firewalls, occupant load, building height and area, and the construction rules ("3.2.2. articles") for Groups C, D, E and F. This chapter covers them in plain language. Confirm exact wording in the Compendium.

Materials, fire separations, closures and firewalls

Heavy timber. Heavy timber construction relies on large, solid wood members with flat surfaces and no thin sections. The minimum member sizes sit in a table, and the article also sets plank floor and roof deck thicknesses, for example a heavy timber floor of plank at least 64 mm thick when splined or tongued and grooved (OBC Div. B 3.1.4.7., Table 3.1.4.7.).

Noncombustible construction and cladding. Where a building must be of noncombustible construction, it is built with noncombustible materials unless one of the listed exceptions applies (3.1.5.1.). Combustible cladding can still be used on such a building if it is not more than 3 storeys or is sprinklered, and the wall assembly passes the fire test described in the article (3.1.5.5.). Foamed plastic insulation in noncombustible construction needs a thermal barrier, such as 12.7 mm gypsum board, masonry or concrete (3.1.5.15.).

Closures. A door or other closure in a fire separation needs a fire-protection rating that matches the separation's fire-resistance rating, read from Table 3.1.8.4.. Note that the closure rating is often lower than the wall rating.

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

Fire dampers sit in the plane of the separation, close on a fusible link or other heat or smoke device, and need an access door for inspection (3.1.8.10.). Hold-open devices are allowed on most closures, but they must release on the right signal. Where there is no fire alarm system, a door such as an exit door must release on a smoke alarm on either side of the separation, within 1.5 m of the opening (3.1.8.14.). Combustible drain, waste and vent piping may pass through a rated separation only with a firestop having an F rating at least equal to the separation, and never in a vertical service space (3.1.9.4.).

Firewalls. A firewall is a noncombustible fire separation that subdivides a building or separates two buildings (Div. A definition). Key numbers from 3.1.10.2. and 3.1.10.4.:

Item	Value
Rating where Group E or F-1/F-2 floor areas are separated	4 h
Rating for other occupancies	2 h
Parapet above roof, 2 h firewall	150 mm
Parapet above roof, 4 h firewall	900 mm
Openings in a storey, total width	25% of firewall length

The rating comes from masonry or concrete, except that a 2 h firewall may use another assembly meeting the listed conditions. No parapet is needed where two roofs differ in height by more than 3 m. Openings are limited by 3.1.10.5., and lower-rated framing must not pull the firewall down if it fails (3.1.10.1.).

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Flame spread, occupant load and clearance to conductors

Flame-spread ratings come from the standard test in 3.1.12.1., or may be assigned from MMAH Supplementary Standard SB-2. Combustible light diffusers and lenses may exceed the normal flame-spread limits outside Group A, Division 1, if they meet the conditions in 3.1.13.4.. In a rated corridor or exit shaft, each diffuser must be small (not more than 1 m²) and spaced at least 1.2 m apart.

Occupant load is the number of persons the space is designed for (Div. A definition). Under 3.1.17.1. it is based on fixed seats, on 2 persons per sleeping room in a dwelling unit, or on the design number but not less than the area per person in Table 3.1.17.1.. Where an area serves different uses at different times, use the value that gives more people.

Clearance to power lines. No building goes under existing overhead conductors. Horizontal clearance from the maximum conductor swing is at least 1 m for 750 V or less, 3 m above 750 V up to 46 kV, and 3.7 m above 46 kV up to 69 kV (3.1.20.1.). If the swing of a private line is unknown, assume 1.8 m.

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Building height, area and multiple major occupancies

Height. Building height counts storeys between the roof and the first storey floor (Div. A definition). A rooftop enclosure for elevator machinery, a stair or a service room is not a storey (3.2.1.1.). A mezzanine is not a storey if mezzanines total not more than 40% of the open area of the room and the space above stays open (no partitions over 1,070 mm), or if they total not more than 10% of the floor area. A second, superimposed mezzanine level counts as a storey.

Basements. The floor over a basement must be a fire separation of at least 45 min (3.2.1.4.). Where sprinklers are not otherwise required, a basement is either sprinklered or split into fire compartments of not more than 600 m² (3.2.1.5.). A pitched roof of 60° or more next to occupied space is treated as a wall (3.2.1.3.).

Several major occupancies. Use the height and area of the whole building for every occupancy (3.2.2.5.). If the occupancies share storeys, the most restricted one governs the whole building (3.2.2.6.). If one occupancy sits entirely above another, each portion is treated as if the whole building were that occupancy, and the floor between them is rated for the lower occupancy (3.2.2.7.). A small occupancy that is not more than 10% of the storey's floor area can be ignored for 3.2.2., unless it is Group F, Division 1 or 2 (3.2.2.8.). A retirement home is always a separate major occupancy.

Some steel elements need no fire protection at all, such as a lintel over an opening up to 2 m wide in a loadbearing wall (3.2.2.3.).

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Streets, balconies, roofs and storeys below ground

Every building must face a street (3.2.2.10.). A building "faces" 2 streets when at least 50% of its perimeter is within 15 m of a street, and 3 streets at 75%. More streets means a larger permitted area in the construction tables. A crawl space is treated as a basement if it is over 1.8 m high, used for an occupancy, carries flue pipes, or is a plenum in combustible construction (3.2.2.9.).

Exterior balconies follow the construction type for the building (3.2.2.11.); a roof that supports an occupancy is built like a floor assembly (3.2.2.13.); a 1-storey rooftop enclosure for elevator machinery or a service room needs no rating (3.2.2.14.). Where a building goes more than 1 storey below ground, the basements are sprinklered and the floors below grade are 2 h (3 h for Group E or F-1/F-2) (3.2.2.15.).

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Construction requirements by Group: C, D, E and F

Each 3.2.2. article sets a maximum height and a building area that grows with the streets faced. 3.2.2.18. lists the articles that need sprinklers; none below is on that list. Selected values:

Article	Use	1 storey, 1 street	Floors
3.2.2.54.	Group C, up to 3 storeys	1,800 m²	45 min fire separation
3.2.2.62.	Group D, up to 3 storeys	4,800 m²	fire separation, 45 min if combustible
3.2.2.68.	Group E, up to 3 storeys	1,500 m²	45 min fire separation
3.2.2.80.	Group F-2, up to 2 storeys	1,000 m²	fire separation, 45 min if combustible
3.2.2.87.	Group F-3, up to 2 storeys	1,600 m²	fire separation, 45 min if combustible

Related articles are 3.2.2.64. (Group D, 2 storeys; its Compendium heading mentions sprinklers, but neither the article text nor 3.2.2.18. calls for them, so check the current wording), 3.2.2.70. (Group E, 2 storeys) and 3.2.2.89. (Group F-3, 1 storey, heavy timber or noncombustible, up to 5,600 m² facing one street).

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Common traps

Mixing up the closure rating and the wall rating: a 1 h wall takes a 45 min door.
Using the floor area of one storey instead of building area (the largest horizontal area above grade).
Forgetting that the 10% exception never applies to Group F, Division 1 or 2.
Rating the floor between stacked occupancies for the upper occupancy. It is the lower one.
Reading the wrong row (number of storeys) or column (streets faced) in the area tables.

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
Materials, fire separations, closures and firewalls	Noncombustible construction and cladding.
Flame spread, occupant load and clearance to conductors	Flame-spread ratings come from the standard test in, or may be assigned from MMAH Supplementary Standard SB-2. Combustible light diffusers and lenses may exceed the normal…
Building height, area and multiple major occupancies	Some steel elements need no fire protection at all, such as a lintel over an opening up to 2 m wide in a loadbearing wall.
Streets, balconies, roofs and storeys below ground	Every building must face a street.
Construction requirements by Group: C, D, E and F	Each 3.2.2. article sets a maximum height and a building area that grows with the streets faced.

Materials, fire separations, closures and firewalls
Noncombustible construction and cladding.
Flame spread, occupant load and clearance to conductors
Flame-spread ratings come from the standard test in, or may be assigned from MMAH Supplementary Standard SB-2. Combustible light diffusers and lenses may exceed the normal…
Building height, area and multiple major occupancies
Some steel elements need no fire protection at all, such as a lintel over an opening up to 2 m wide in a loadbearing wall.
Streets, balconies, roofs and storeys below ground
Every building must face a street.
Construction requirements by Group: C, D, E and F
Each 3.2.2. article sets a maximum height and a building area that grows with the streets faced.

Usual exam traps

Mixing up the closure rating and the wall rating: a 1 h wall takes a 45 min door.
Using the floor area of one storey instead of building area (the largest horizontal area above grade).
Forgetting that the 10% exception never applies to Group F, Division 1 or 2.
Rating the floor between stacked occupancies for the upper occupancy. It is the lower one.
Reading the wrong row (number of storeys) or column (streets faced) in the area tables.

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Questions on Part 3 classification, construction and building size, 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 Small Buildings calculations

Code cited in this chapter

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

OBC Div. B 3.1.4.7. Heavy Timber Construction
(1)Wood elements in heavy timber construction shall be arranged in heavy solid masses and with essentially smooth flat surfaces to avoid thin sections and sharp projections.
(2)Except as permitted by Sentences (3) to (6) and (12), the minimum dimensions of wood elements in heavy timber construction shall conform to Table 3.1.4.7.
(3)Where splice plates are used at splices of roof arches supported on the tops of walls or abutments, roof trusses, roof beams and roof girders in heavy timber construction, they shall be not less than 64 mm thick.
(4)Floors in heavy timber construction shall be of glued-laminated or solid sawn plank not less than
(a)64 mm thick, splined or tongued and grooved, or
(b)38 mm wide and 89 mm deep set on edge and well-spiked together.
(5)Floors in heavy timber construction shall be laid
(a)so that no continuous line of end joints will occur except at points of support, and covered with
(i)tongued and grooved flooring not less than 19 mm thick laid crosswise or diagonally, or
(ii)tongued and grooved phenolic-bonded plywood, strandboard or waferboard not less than 12.5 mm thick, and
(b)not closer than 15 mm to the walls to provide for expansion, with the gap covered at the top or bottom.
(6)Roofs in heavy timber construction shall be of tongued and grooved phenolic-bonded plywood, strandboard or waferboard not less than 28 mm thick, or glued-laminated or solid sawn plank that is
(a)not less than 38 mm thick, splined or tongued and grooved, or
(b)not less than 38 mm wide and 64 mm deep set on edge and laid so that no continuous line of end joints will occur except at the points of support.
(7)Wood columns in heavy timber construction shall be continuous or superimposed throughout all storeys.
(8)Superimposed wood columns in heavy timber construction shall be connected by
(a)reinforced concrete or metal caps with brackets,
(b)steel or iron caps with pintles and base plates, or
(c)timber splice plates fastened to the columns by metal connectors housed within the contact faces.
(9)Where beams and girders in heavy timber construction enter masonry, wall plates, boxes of the self-releasing type or hangers shall be used.
(10)Wood girders and beams in heavy timber construction shall be closely fitted to columns, and adjoining ends shall be connected by ties or caps to transfer horizontal loads across the joints.
(11)In heavy timber construction, intermediate wood beams used to support a floor shall be supported on top of the girders or on metal hangers into which the ends of the beams are closely fitted.
(12)Roof arches supported on the tops of walls or abutments, roof trusses, roof beams and roof girders in heavy timber construction are permitted to be not less than 64 mm wide provided
(a)where two or more spaced members are used, the intervening spaces are
(i)blocked solidly throughout, or
(ii)tightly closed by a continuous wood cover plate not less than 38 mm thick secured to the underside of the members, or
(b)the underneath of the roof deck or sheathing is sprinklered.
Open OBC Div. B 3.1.4.7. in the code viewer
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).
Open OBC Div. B 3.1.5.1. 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 3.1.5.15. Foamed Plastic Insulation)
(1)Foamed plastic insulation is permitted to be installed above roof decks, outside of foundation walls below ground level and beneath concrete slabs-on-ground of a building required to be of noncombustible construction.
(2)Except as provided in Sentences (3), (4) and 3.1.5.7.(1), foamed plastic insulation with a flame-spread rating not more than 500 on any exposed surface, or any surface that would be exposed by cutting through the material in any direction, is permitted in a building required to be of noncombustible construction, provided the insulation is protected from adjacent space in the building, other than adjacent concealed spaces within wall assemblies, by a thermal barrier consisting of
(a)not less than 12.7 mm thick gypsum board mechanically fastened to a supporting assembly independent of the insulation,
(b)lath and plaster, mechanically fastened to a supporting assembly independent of the insulation,
(c)masonry,
(d)concrete, or
(e)any thermal barrier that meets the requirements of classification B when tested in conformance with CAN/ULC-S124, "Standard Method of Test for the Evaluation of Protective Coverings for Foamed Plastic".
(3)Foamed plastic insulation with a flame-spread rating more than 25 but not more than 500 on any exposed surface, or any surface that would be exposed by cutting through the material in any direction, is permitted in the exterior walls of a building required to be of noncombustible construction that is not sprinklered and is more than 18 m high, measured from grade to the underside of the roof, provided the insulation is protected from adjacent space in the building, other than adjacent concealed spaces within wall assemblies, by a thermal barrier consisting of
(a)gypsum board not less than 12.7 mm thick, mechanically fastened to a supporting assembly independent of the insulation and with all joints either backed or taped and filled,
(b)lath and plaster, mechanically fastened to a supporting assembly independent of the insulation,
(c)masonry or concrete not less than 25 mm thick, or
(d)any thermal barrier that, when tested in conformance with CAN/ULC-S101, "Standard Method of Fire Endurance Tests of Building Construction and Materials," does not develop an average temperature rise more than 140°C or a maximum temperature rise more than 180°C at any point on its unexposed face within 10 min. (See Note A-3.1.5.14.(5)(d)) (See also Article 3.2.3.7.)
(4)Foamed plastic insulation with a flame-spread rating more than 25 but not more than 500 on any exposed surface, or any surface that would be exposed by cutting through the material in any direction, is permitted in the interior walls, within ceilings and within roof assemblies of a building required to be of noncombustible construction that is not sprinklered and is more than 18 m high, measured from grade to the underside of the roof, provided the insulation is protected from adjacent space in the building, other than adjacent concealed spaces within wall assemblies, by a thermal barrier consisting of
(a)Type X gypsum board not less than 15.9 mm thick, mechanically fastened to a supporting assembly independent of the insulation and with all joints either backed or taped and filled, conforming to
(i)ASTM C1177 / C1177 M, "Standard Specification for Glass Mat Gypsum Substrate for Use as Sheathing,
(ii)ASTM C1178 / C1178 M, "Standard Specification for Coated Glass Mat Water-Resistant Gypsum Backing Panel,"
(iii)ASTM C1396 / C1396 M, "Standard Specification for Gypsum Board," or
(iv)CAN/CSA-A82.27-M, "Gypsum Board,"
(b)non-loadbearing masonry or concrete not less than 50 mm thick,
(c)loadbearing masonry or concrete not less than 75 mm thick, or
(d)any thermal barrier that, when tested in conformance with CAN/ULC-S101, "Standard Method of Fire Endurance Tests of Building Construction and Materials,"
(i)does not develop an average temperature rise more than 140°C or a maximum temperature rise more than 180°C at any point on its unexposed face within 20 min, and
(ii)remains in place for not less than 40 min.
Open OBC Div. B 3.1.5.15. in the code viewer
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
Open OBC Div. B Table 3.1.8.4. in the code viewer
OBC Div. B 3.1.8.10. Installation of Fire Dampers
(1)A fire damper shall be installed in the plane of the fire separation so as to stay in place should the duct become dislodged during a fire. (See Note A-3.1.8.10.(1))
(2)A fire damper shall be arranged so as to close automatically upon the operation of a fusible link conforming to ULC-S505, "Standard for Fusible Links for Fire Protection Services," or other heat-actuated or smoke-actuated device.
(3)A heat-actuated device referred to in Sentence (2) shall
(a)be located where it is readily affected by an abnormal rise of temperature in the duct, and
(b)have a temperature rating approximately 30°C above the maximum temperature that would exist in the system either with the system in operation or shut down.
(4)A fire damper tested in the vertical or horizontal position shall be installed in the position in which it was tested.
(5)A tightly fitted access door shall be installed for each fire damper to provide access for the inspection of the damper and the resetting of the release device. (See Note A-3.1.8.10.(5))
Open OBC Div. B 3.1.8.10. in the code viewer
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).
Open OBC Div. B 3.1.8.14. in the code viewer

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OBC Div. B 3.1.9.4. Combustible Piping Penetrations
(1)Combustible sprinkler piping is permitted to penetrate a fire separation provided the fire compartments on each side of the fire separation are sprinklered.
(2)Combustible water distribution piping is permitted to penetrate a fire separation that is required to have a fire-resistance rating, provided the piping is protected at the penetration with a firestop in conformance with Clause (4)(a) or (b).
(3)Except as permitted by Sentences (4), (5), (7) and (8), combustible piping shall not be used in a drain, waste and vent piping system if any part of that system penetrates
(a)a fire separation required to have a fire-resistance rating, or
(b)a membrane that forms part of an assembly required to have a fire-resistance rating.
(4)Combustible drain, waste and vent piping is permitted to penetrate a fire separation required to have a fire-resistance rating or a membrane that forms part of an assembly required to have a fire-resistance rating, provided
(a)except as provided in Clause (b), the piping is sealed at the penetration by a firestop that has an F rating not less than the fire-resistance rating required for the fire separation when subjected to the fire test method in CAN/ULC-S115, "Standard Method of Fire Tests of Firestop Systems,"
(b)in buildings more than 3 storeys in building height, the piping is sealed at the penetration by a firestop that has an F rating not less than the fire-resistance rating required for the fire separation when subjected to the fire test method in CAN/ULC-S115, "Standard Method of Fire Tests of Firestop Systems," with a pressure differential of 50 Pa between the exposed and unexposed sides, with the higher pressure on the exposed side, and
(c)the piping is not located in a vertical service space.
(5)Combustible drain, waste and vent piping is permitted on one side of a vertical fire separation provided it is not located in a vertical service space.
(6)Combustible piping for central vacuum systems is permitted to penetrate a fire separation, provided the installation conforms to the requirements that apply to combustible drain, waste and vent piping specified in Sentence (4).
(7)Except as provided in Sentence (8), penetrations of a fire separation that incorporate transitions between combustible and noncombustible drain, waste and vent piping shall be sealed by a firestop that has an F rating not less than the fire-resistance rating required for the fire separation when subjected to the fire test method in CAN/ULC-S115, "Standard Method of Fire Tests of Firestop Systems," with a pressure differential of 50 Pa between the exposed and unexposed sides, with the higher pressure on the exposed side.
(8)Transitions between vertical noncombustible drain, waste and vent piping and combustible branches for drain, waste and vent piping are permitted on either side of a fire separation, provided they are not located in a vertical service space. (See Note A-3.1.9.4.(8))
(9)Combustible piping not more than 25 mm in diameter containing chlorine gas is permitted to penetrate a fire separation between a chlorine gas service room built in conjunction with a public pool or public spa and the remainder of the building, provided the piping is sealed at the penetration by a firestop in conformance with Clause 3.1.9.1.(1)(a).
Open OBC Div. B 3.1.9.4. in the code viewer
OBC Div. A 1.4.1.2.(1) Firewall
Firewall means a type of fire separation of noncombustible construction that subdivides a building or separates adjoining buildings to resist the spread of fire and that has a fire-resistance rating as prescribed in this Code and has structural stability to remain intact under fire conditions for the required fire-rated time.
Open OBC Div. A 1.4.1.2.(1) in the code viewer
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 3.1.10.1. Prevention of Firewall Collapse
(1)Except as permitted by Sentence (2), the connections and supports for structural framing members that are connected to or supported on a firewall and have a fire-resistance rating less than that required for the firewall, shall be designed so that the failure of the framing systems during a fire will not affect the integrity of the firewall during the fire.
(2)Sentence (1) does not apply to a firewall consisting of two separate wall assemblies each tied to its respective building frame but not to each other, provided each wall assembly is
(a)a fire separation having one-half of the fire-resistance rating required for the firewall by Sentences 3.1.10.2.(1) and (2), and
(b)designed so that the collapse of one wall assembly will not cause collapse of the other.
(3)A firewall is permitted to be supported on the structural frame of a building of noncombustible construction provided the supporting frame has a fire-resistance rating not less than that required for the firewall.
(4)Piping, ducts and totally enclosed noncombustible raceways shall be installed so that their collapse will not cause collapse of the firewall.
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OBC Div. B 3.1.12.1. Determination of Ratings
(1)Except as required by Sentence (2) and as permitted by Sentence (3), the flame-spread rating and smoke developed classification of a material, assembly, or structural member shall be determined on the basis of not less than three tests conducted in conformance with CAN/ULC-S102, "Standard Method of Test for Surface Burning Characteristics of Building Materials and Assemblies."
(2)The flame-spread rating and smoke developed classification of a material or assembly shall be determined on the basis of not less than three tests conducted in conformance with CAN/ULC-S102.2, "Standard Method of Test for Surface Burning Characteristics of Flooring, Floor Coverings, and Miscellaneous Materials and Assemblies," if the material or assembly
(a)is designed for use in a relatively horizontal position with only its top surface exposed to air,
(b)cannot be tested in conformance with Sentence (1) without the use of supporting material that is not representative of the intended installation, or
(c)is thermoplastic.
(3)A material, assembly, or structural member is permitted to be assigned a flame-spread rating and smoke developed classification on the basis of MMAH Supplementary Standard SB-2, "Fire Performance Ratings."
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OBC Div. B 3.1.13.4. Light Diffusers and Lenses
(1)The flame-spread rating of combustible light diffusers and lenses in all occupancies other than Group A, Division 1 is permitted to be more than the flame-spread rating limits required elsewhere in this Subsection, provided the light diffusers and lenses
(a)have a flame-spread rating not more than 250 and a smoke developed classification not more than 600 when tested in conformance with CAN/ULC-S102.2, "Standard Method of Test for Surface Burning Characteristics of Flooring, Floor Coverings, and Miscellaneous Materials and Assemblies,"
(b)fall to the bottom of the test apparatus before igniting when tested in conformance with CAN/ULC-S102.3, "Standard Method of Fire Test of Light Diffusers and Lenses,"
(c)are not prevented from falling from the ceiling by construction located beneath the elements, and
(d)are not used in a corridor that is required to be separated from the remainder of the building by a fire separation or in an exit shaft unless individual diffusers or lenses are not more than 1 m² in area and are not less than 1.2 m apart.
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OBC Div. A 1.4.1.2.(1) Occupant load
Occupant load means the number of persons for which a building or part thereof is designed.
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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 Table 3.1.17.1. Occupant Load
Table 3.1.17.1. Occupant Load Forming Part of Article 3.1.17.1. Type of Use of Floor Area or Part Thereof | Area per Person, m[2] Assembly uses | N/A space with fixed seats | [1] space with non-fixed seats | 0.75 stages for theatrical performances | 0.75 space with non-fixed seats and tables | 0.95 standing space | 0.40 stadia and grandstands | 0.60 bowling alleys, pool and billiard rooms | 9.30 classrooms | 1.85 school shops and vocational rooms | 9.30 reading or writing rooms or lounges | 1.85 dining, beverage and cafeteria space | 1.20 laboratories in schools | 4.60 Care, care and treatment or detention uses | N/A B-1 : detention quarters | 11.60 B-2 : treatment and sleeping areas | 10.00 B-3 : sleeping room areas | 10.00 (See also Article 3.7.1.3.) | (See also Article 3.7.1.3.) Residential uses | N/A dwelling units | [2] dormitories | 4.60 Business and personal services uses | N/A personal service shops | 4.60 offices | 9.30 Mercantile uses | N/A basements and first storeys | 3.70 second storeys having a principal entrance from a pedestrian thoroughfare or a parking area | 3.70 other storeys | 5.60 Industrial uses | N/A manufacturing or process rooms | 4.60 storage garages | 46.00 storage spaces (warehouse) | 28.00 aircraft hangars | 46.00 Other uses | N/A cleaning and repair goods | 4.60 kitchens | 9.30 storage | 46.00 public corridors intended for occupancies in addition to pedestrian travel | 3.70[3] Notes to Table 3.1.17.1.: (1) See Clause 3.1.17.1.(1)(a). (2) See Clause 3.1.17.1.(1)(b) (3) See Note A-3.3.
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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. A 1.4.1.2.(1) Building height (in storeys)
Building height (in storeys) means the number of storeys contained between the roof and the floor of the first storey.
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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))
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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.
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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).
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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.
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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.
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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.
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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.
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OBC Div. B 3.2.2.8. Exceptions for Major Occupancies
(1)In a building in which the aggregate area of all major occupancies in a particular Group or Division is not more than 10% of the floor area of the storey in which they are located, these major occupancies need not be considered as major occupancies for the purposes of this Subsection, provided they are not classified as Group F, Division 1 or 2 occupancies.
(2)For the purposes of Sentence (1), a retirement home is deemed to be a separate major occupancy.
(3)A helicopter landing area on the roof of a building need not be considered a major occupancy for purposes of Subsection 3.2.2. where such landing area is not more than 10% of the area of the roof.
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OBC Div. B 3.2.2.3. Exceptions to Structural Fire Protection
(1)Fire protection is not required for
(a)steel lintels above openings not more than 2 m wide in loadbearing walls and not more than 3 m wide in non-loadbearing walls.
(b)steel lintels above openings more than 2 m wide in loadbearing walls and more than 3 m wide in non-loadbearing walls provided the lintels are supported at intervals of not more than 2 m by structural members with the required fire-resistance rating,
(c)the bottom flanges of shelf angles and plates that are not a part of the structural frame,
(d)steel members for framework around elevator hoistway doorways, steel for the support of elevator and dumbwaiter guides, counterweights and other similar equipment, that are entirely enclosed in a hoistway and are not a part of the structural frame of the building,
(e)steel members of stairways and escalators that are not a part of the structural frame of a building,
(f)steel members of porches, exterior balconies, exterior stairways, fire escapes, cornices, marquees and other similar appurtenances, provided they are outside an exterior wall of a building, and
(g)loadbearing steel or concrete members wholly or partly outside a building face in a building not more than 4 storeys in building height and classified as Group A, B, C, D or F, Division 3 major occupancy provided the members are
(i)not less than 1 m away from any unprotected opening in an exterior wall, or
(ii)shielded from heat radiation in the event of a fire within the building by construction that will provide the same degree of protection that would be necessary if the member was located inside the building, with the protection extending on either side of the member a distance equal to the projection of the member from the face of the wall. (See also Article 3.2.3.9.)
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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.
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OBC Div. B 3.2.2.9. Crawl Spaces
(1)For the purposes of Articles 3.1.11.6., 3.2.1.4. and 3.2.1.5., a crawl space shall be considered as a basement if it is
(a)more than 1.8 m high between the lowest part of the floor assembly and the ground or other surface below,
(b)used for any occupancy,
(c)used for the passage of flue pipes, or
(d)used as a plenum in combustible construction.
(2)A floor assembly immediately above a crawl space is not required to be constructed as a fire separation and is not required to have a fire-resistance rating provided the crawl space is not required to be considered as a basement by Sentence (1).
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OBC Div. B 3.2.2.11. Exterior Balconies
(1)Except as provided in Sentence (2), an exterior balcony shall be constructed in accordance with the type of construction required by Articles 3.2.2.20. to 3.2.2.93., as applicable to the occupancy classification of the building.
(2)The floor assembly of an exterior balcony in a building or part thereof conforming to Article 3.2.2.48., 3.2.2.57. or 3.2.2.93. shall
(a)be of noncombustible construction, or
(b)be constructed in accordance with Article 3.1.6.3., but need not comply with Sentence 3.1.6.4.(1).
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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.
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OBC Div. B 3.2.2.14. Rooftop Enclosures
(1)A rooftop enclosure for elevator machinery or for a service room shall be constructed in accordance with the type of construction required by Articles 3.2.2.20. to 3.2.2.93.
(2)A rooftop enclosure for elevator machinery or for a service room, not more than 1 storey high, is not required to have a fire-resistance rating.
(3)A rooftop enclosure for a stairway shall be constructed in accordance with the type of construction required by Articles 3.2.2.20, to 3.2.2.93.
(4)A rooftop enclosure for a stairway need not have a fire-resistance rating nor be constructed as a fire separation.
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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.
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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))
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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 3.2.2.62. Group D, up to 3 Storeys
(1)A building classified as Group D is permitted to conform to Sentence (2) provided
(a)it is not more than 3 storeys in building height, and
(b)it has a building area not more than the value in Table 3.2.2.62.
(2)The building referred to in Sentence (1) is permitted to be of combustible construction or noncombustible construction used singly or in combination, and
(a)floor assemblies shall be fire separations and, if of combustible construction, shall have a fire-resistance rating not less than 45 min,
(b)mezzanines shall have, if of combustible construction, a fire-resistance rating not less than 45 min,
(c)roof assemblies shall have, if of combustible construction, a fire-resistance rating not less than 45 min, except that in a building not more than 1 storey in building height, the fire-resistance rating is permitted to be waived provided the roof assembly is constructed as a fire-retardant-treated wood roof system conforming to Article 3.1.14.1., and the building area is not more than
(i)2,400 m² if facing one street,
(ii)3,000 m² if facing 2 streets, or
(iii)3,600 m² if facing 3 streets, and
(d)loadbearing walls, columns and arches supporting an assembly required to have a fire-resistance rating shall
(i)have a fire-resistance rating not less than 45 min, or
(ii)be of noncombustible construction.
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OBC Div. B 3.2.2.68. 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 3.2.2.80. Group F, Division 2, up to 2 Storeys
(1)A building classified as Group F, Division 2 is permitted to conform to Sentence (2) provided
(a)it is not more than 2 storeys in building height, and
(b)it has a building area not more than the value in Table 3.2.2.80.
(2)The building referred to in Sentence (1) is permitted to be of combustible construction or noncombustible construction used singly or in combination, and
(a)floor assemblies shall be fire separations and, if of combustible construction, shall have a fire-resistance rating not less than 45 min, and
(b)loadbearing walls, columns and arches supporting an assembly required to have a fire-resistance rating shall
(i)have a fire-resistance rating not less than 45 min, or
(ii)be of noncombustible construction.
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OBC Div. B 3.2.2.87. Group F, Division 3, up to 2 Storeys
(1)A building classified as Group F, Division 3 is permitted to conform to Sentence (2) provided
(a)it is not more than 2 storeys in building height, and
(b)it has a building area not more than the value in Table 3.2.2.87.
(2)The building referred to in Sentence (1) is permitted to be of combustible construction or noncombustible construction used singly or in combination, and
(a)floor assemblies shall be fire separations and, if of combustible construction, shall have a fire-resistance rating not less than 45 min, and
(b)loadbearing walls, columns and arches supporting an assembly required to have a fire-resistance rating shall
(i)have a fire-resistance rating not less than 45 min, or
(ii)be of noncombustible construction.
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OBC Div. B 3.2.2.64. Group D, up to 2 Storeys, Sprinklered
(1)A building classified as Group D is permitted to conform to Sentence (2) provided
(a)it is not more than 2 storeys in building height, and
(b)it has a building area not more than the value in Table 3.2.2.64.
(2)The building referred to in Sentence (1) is permitted to be of combustible construction or noncombustible construction used singly or in combination, and
(a)floor assemblies shall be fire separations and, if of combustible construction, shall have a fire-resistance rating not less than 45 min, and
(b)loadbearing walls, columns and arches supporting an assembly required to have a fire-resistance rating shall
(i)have a fire-resistance rating not less than 45 min, or
(ii)be of noncombustible construction.
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OBC Div. B 3.2.2.70. Group E, up to 2 Storeys
(1)A building classified as Group E is permitted to conform to Sentence (2) provided
(a)it is not more than 2 storeys in building height, and
(b)it has a building area not more than the value in Table 3.2.2.70.
(2)The building referred to in Sentence (1) is permitted to be of combustible construction or noncombustible construction used singly or in combination, and
(a)floor assemblies shall be fire separations with a fire-resistance rating not less than 45 min, and
(b)loadbearing walls, columns and arches shall have a fire-resistance rating not less than that required for the supported assembly.
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OBC Div. B 3.2.2.89. Group F, Division 3, One Storey
(1)A building classified as Group F, Division 3 is permitted to be of heavy timber 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
(i)5,600 m² if facing one street,
(ii)7,000 m² if facing 2 streets, or
(iii)8,400 m² if facing 3 streets.
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OBC Div. B Table 3.2.2.54. Maximum Building Area
Table 3.2.2.54. Maximum Building Area Forming Part of Sentence 3.2.2.54.(1) No. of Storeys | Maximum area, m² — Facing 1 Street | Maximum area, m² — Facing 2 Streets | Maximum area, m² — Facing 3 Streets 1 | 1,800 | 2,250 | 2,700 2 | 900 | 1,125 | 1,350 3 | 600 | 750 | 900
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