Fire-resistance ratings, fire separations, penetrations, firewalls and fire blocks (Fire Protection)

Last updated October 22, 2026

Values this chapter turns on

firewall rating with Group E, F1 or F2 on a side: 4 h; firewall rating with Group E, F1 or F2 on a side
closure rating in a 2 h fire separation: 1.5 h; closure rating in a 2 h fire separation
max closure opening if either side unsprinklered: 11 m²; max closure opening if either side unsprinklered
max horizontal run of a fire-blocked wall cavity: 20 m; max horizontal run of a fire-blocked wall cavity

This section is the toolkit of passive fire protection: how ratings are established, how a fire separation stays continuous, what protects openings in it, how services may pass through it, what makes a firewall special and where fire blocks go in concealed spaces. Questions here are mostly direct lookups with numbers, so know where each Article sits in Subsections 3.1.7. to 3.1.11.

Fire-resistance ratings

A rating comes from a CAN/ULC-S101 test, or may be assigned from Supplementary Standard SB-2 (OBC Div. B 3.1.7.1.). The side of exposure matters (3.1.7.3.):

Assembly	Rated for fire exposure from
Floors, roofs, ceilings	the underside
Firewalls and interior vertical fire separations	each side
Exterior walls	inside the building

An exterior wall with a limiting distance of 1.2 m or more escapes the unexposed-side temperature rise limit, if a radiation correction is made (3.1.7.2.). Supporting construction must match: 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 (3.1.7.5.). Over-providing a rating never creates an obligation to exceed the minimum elsewhere (3.1.7.4.).

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Fire separations and closures

A required fire separation is a continuous element, and openings in it are protected by closures (OBC Div. B 3.1.8.1.). Continuity means a concealed space above a vertical fire separation is divided at the separation, and joints where a rated separation meets a floor, ceiling, roof or another separation are sealed by a firestop with a matching FT rating (3.1.8.3.).

Closure ratings. Table 3.1.8.4. links the separation rating to the closure rating. The pattern is mostly "one step down":

Fire separation	Closure (selected)
45 min or 1 h	45 min
2 h	1.5 h
3 h	2 h

A 20 min door is enough in separations up to 1 h between a public corridor and a suite, a corridor and sleeping rooms, or corridor and classrooms/offices in A2, and in any separation up to 45 min in buildings up to 3 storeys (3.1.8.12.). Those doors have tight clearances: 6 mm at the bottom, 3 mm at sides and top.

Opening size (3.1.8.6.): 11 m² and no dimension over 3.7 m if either side is unsprinklered; 22 m² and 6 m if both sides are sprinklered.

Doors. Every door in a fire separation needs a self-closer (exceptions for some classrooms, small business suites and hospital sleeping rooms) and a positive latch (3.1.8.13., 3.1.8.15.). Hold-open devices are allowed except on exit stair doors in buildings over 3 storeys and on 3.3.5.7. vestibule doors; with a fire alarm system they release on any signal from a single-stage system or on the alert signal (or an adjacent smoke detector) in a 2-stage system, and on exit doors, public corridor doors and doors serving assembly, care, detention or residential occupancies they release on a smoke detector (3.1.8.14.).

Dampers. A fire damper goes where a duct penetrates a fire separation, unless waived in 3.1.8.8.; smoke or combination smoke/fire dampers are added where the separation serves a public corridor or an assembly, care, detention or residential occupancy (3.1.8.7.). Fire dampers sit in the plane of the separation; combination dampers in a duct within 610 mm of it (3.1.8.10., 3.1.8.11.).

Glass in closures. Wired glass and glass block may protect openings in separations up to 1 h (3.1.8.16.). Table 3.1.8.17. limits door temperature rise and glazing area by location: for example 0.8 m² of glazing in an exit enclosure door in buildings up to 3 storeys, but 0.0645 m² above that.

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Penetrations and firestops

Penetrations of a fire separation or rated membrane are sealed by a firestop with an F rating at least equal to the separation, tested to CAN/ULC-S115, or cast in place for steel, copper, concrete or masonry items (OBC Div. B 3.1.9.1.). Penetrations of firewalls, and of horizontal separations under 3.2.1.2., need the stricter FT rating. A sprinkler needs no firestop if a metal escutcheon plate per NFPA 13 covers the gap.

Item	Key rule
Noncombustible outlet box, no firestop	max 0.016 m² each, 0.065 m² per 9.3 m², gap max 3 mm (3.1.9.3.)
Boxes on opposite sides of a rated wall	600 mm apart, or fire block, or firestop
Combustible sprinkler pipe	both sides sprinklered (3.1.9.4.)
Combustible DWV pipe	F-rated firestop; over 3 storeys, tested at 50 Pa; never in a vertical service space
Embedded combustible raceway	50 mm concrete cover below (3.1.9.2.)

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Firewalls

A firewall is 4 h noncombustible where either side has Group E, F1 or F2 floor areas, otherwise 2 h (OBC Div. B 3.1.10.2.). The rating must come from masonry or concrete, except that a 2 h firewall may use other construction if it is protected from damage, performs as well as masonry, does not separate B1 or B2 occupancies, and, where it separates a high building or a 3.2.2.51. or 3.2.2.60. building from another building, has sprinklered buildings on both sides. Framing that rests on a firewall must be able to collapse without taking the wall down, or a double firewall (each half rated at half the value) is used (3.1.10.1.). A firewall runs from the ground through all storeys; it may stop under a concrete roof slab rated 1 h (for a 2 h firewall) or 2 h (for a 4 h firewall) with no concealed spaces above the wall (3.1.10.3.).

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Fire blocks in concealed spaces

Fire blocks separate interior wall, ceiling and crawl space cavities from exterior wall and attic cavities (3.1.11.1.). Key limits:

Concealed space	Maximum compartment
Wall cavity	every floor level, 20 m horizontal, 3 m vertical (3.1.11.2.)
Unsprinklered combustible floor or roof, flame spread 25 or less	600 m², 60 m (3.1.11.5.)
Same, flame spread over 25	300 m², 20 m
Crawl space not considered a basement	600 m², 30 m (3.1.11.6.)

Fire blocks must hold 15 min under CAN/ULC-S101, or be 12.7 mm gypsum board, 0.38 mm sheet steel, or in combustible buildings 38 mm lumber or 12.5 mm panels (3.1.11.7.).

Common traps: confusing a fire block (inside concealed spaces) with a firestop (at fire separations and penetrations); using the farm building 900 m² limit in a Part 3 question.

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Chapter review

Chapter at a glance

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

Chapter at a glance: the key idea in each section
Section	Key idea
Fire-resistance ratings	An exterior wall with a limiting distance of 1.2 m or more escapes the unexposed-side temperature rise limit, if a radiation correction is made.
Fire separations and closures	A required fire separation is a continuous element, and openings in it are protected by closures.
Penetrations and firestops	Penetrations of a fire separation or rated membrane are sealed by a firestop with an F rating at least equal to the separation, tested to CAN/ULC-S115, or cast in place for steel…
Firewalls	A firewall is 4 h noncombustible where either side has Group E, F1 or F2 floor areas, otherwise 2 h.
Fire blocks in concealed spaces	Fire blocks separate interior wall, ceiling and crawl space cavities from exterior wall and attic cavities.

Fire-resistance ratings
An exterior wall with a limiting distance of 1.2 m or more escapes the unexposed-side temperature rise limit, if a radiation correction is made.
Fire separations and closures
A required fire separation is a continuous element, and openings in it are protected by closures.
Penetrations and firestops
Penetrations of a fire separation or rated membrane are sealed by a firestop with an F rating at least equal to the separation, tested to CAN/ULC-S115, or cast in place for steel…
Firewalls
A firewall is 4 h noncombustible where either side has Group E, F1 or F2 floor areas, otherwise 2 h.
Fire blocks in concealed spaces
Fire blocks separate interior wall, ceiling and crawl space cavities from exterior wall and attic cavities.

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Questions on Fire-resistance ratings, fire separations, penetrations, firewalls and fire blocks, 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 3.1.7.1. Determination of Ratings
(1)Except as permitted by Sentence (2) and Articles 3.1.7.2. and 3.6.3.5., the rating of a material, assembly of materials or a structural member that is required to have a fire-resistance rating, shall be determined on the basis of the results of tests conducted in conformance with CAN/ULC-S101, "Standard Method of Fire Endurance Tests of Building Construction and Materials."
(2)A material, assembly of materials or a structural member is permitted to be assigned a fire-resistance rating on the basis of MMAH Supplementary Standard SB-2, "Fire Performance Ratings."
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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 3.1.7.2. Exception for Exterior Walls
(1)The limit on the rise of temperature on the unexposed surface of an assembly as required by the tests referred to in Sentence 3.1.7.1.(1) shall not apply to an exterior wall that has a limiting distance of 1.2 m or more, provided correction is made for radiation from the unexposed surface in accordance with Sentence 3.2.3.1.(9).
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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 3.1.7.4. Minimum Fire-Resistance Rating
(1)The use of materials or assemblies having a greater fire-resistance rating than required shall impose no obligation to exceed in whole or in part the minimum fire-resistance ratings required by this Part.
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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 3.1.8.3. Continuity of Fire Separations
(1)Except as permitted by Sentence 3.6.4.2.(2), a horizontal service space or other concealed space located above a required vertical fire separation, including the walls of a vertical shaft, shall be divided at the fire separation by an equivalent fire separation within the service space.
(2)Except as provided in Sentence (5), the continuity of a fire separation having a fire-resistance rating that abuts another fire separation, a floor, a ceiling, or a roof shall be maintained by a firestop conforming to Sentence (3). (See Note A-3.1.8.3.(2))
(3)The firestop required in Sentence (2) shall have an FT rating not less than the fire-resistance rating of the abutting fire separation when subjected to the fire test method in CAN/ULC-S115, "Standard Method of Fire Tests of Firestop Systems."
(4)Except as provided in Sentence (5), joints located in a horizontal plane between a floor and an exterior wall shall be sealed by a firestop that, when subjected to the fire test method in ASTM E2307, "Standard Test Method for Determining Fire Resistance of Perimeter Fire Barriers Using Intermediate-Scale, Multi-storey Test Apparatus," has an F rating not less than the fire-resistance rating of the horizontal fire separation.
(5)Joints between ceilings and walls, between floors and walls, and between walls at corners need not comply with Sentences (2) and (4) where such joints consist of gypsum board that is attached to framing members and arranged so as to restrict the passage of flame and smoke through the joints. (See Note A-3.1.8.3.(5))
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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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Show all 32 articles

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 3.1.8.13. Self-Closing Devices
(1)Except as provided in Sentences (3) to (5) and 3.3.3.2.(5), every door in a fire separation, other than doors to freight elevators and dumbwaiters, shall be equipped with a self-closing device designed to return the door to the closed position after each use.
(2)Reserved.
(3)In a building that is not more than 3 storeys in building height, a self-closing device is not required on a door that is located between a classroom and a corridor providing access to exit from the classroom, except that a self-closing device is required on a door between a hazardous classroom and the corridor in an elementary or secondary school.
(4)In a building that is not more than 3 storeys in building height, a self-closing device is not required on a door between a public corridor and an adjacent room or suite of business and personal services occupancy if the door is not located in.
(a)a dead-end portion of the corridor, or
(b)a corridor that serves a hotel.
(5)Within a fire compartment in a hospital or long-term care home that complies with the requirements of Article 3.3.3.5., a self-closing device is not required on a door that is located between
(a)a patient's or resident's sleeping room and a corridor serving the patient's or resident's sleeping room, or
(b)a patient's or resident's sleeping room and an adjacent room that serves the patient's or resident's sleeping room.
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OBC Div. B 3.1.8.15. Door Latches
(1)Except as permitted by Sentence 3.3.3.2.(5) and Article 3.3.3.5., a swing-type door in a fire separation shall be equipped with a positive latching mechanism designed to hold the door in the closed position after each use.
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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 3.1.8.7. Location of Fire Dampers and Smoke Dampers
(1)Except as provided in Article 3.1.8.8., a fire damper having a fire-protection rating conforming to Sentence 3.1.8.4.(2) shall be installed in conformance with Article 3.1.8.10. in ducts or air-transfer openings that penetrate an assembly required to be a fire separation.
(2)Except as provided in Article 3.1.8.9., a smoke damper or a combination smoke/fire damper shall be installed in conformance with Article 3.1.8.11. in ducts or air-transfer openings that penetrate an assembly required to be a fire separation, where the fire separation
(a)separates a public corridor,
(b)contains an egress door referred to in Sentence 3.4.2.4.(2),
(c)serves an assembly, care, care and treatment, detention or residential occupancy, or
(d)is installed to meet the requirements of Clause 3.3.1.7.(1)(b) or Sentence 3.3.3.5.(4). or 3.3.4.11.(4).
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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))
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OBC Div. B 3.1.8.11. Installation of Smoke Dampers
(1)Where smoke dampers are used as a closure in an air-transfer opening, they shall be installed in the plane of the fire separation.
(2)Where combination smoke/fire dampers are used as a closure in a duct, they shall be installed within 610 mm of the plane of the fire separation, provided there is no inlet or outlet opening between the fire separation and the damper.
(3)Except as required by a smoke control system, smoke dampers and combination smoke/fire dampers shall be configured so as to close automatically upon a signal from an adjacent smoke detector located as described in CAN/ULC-S524, "Standard for Installation of Fire Alarm Systems," within 1.5 m horizontally of the duct or air-transfer opening in the fire separation
(a)on both sides of the air-transfer opening, or
(b)in the duct downstream of the smoke damper or combination smoke/fire damper.
(4)Smoke dampers or combination smoke/fire dampers shall be installed in the vertical or horizontal position in which they were tested.
(5)A tightly fitted access door shall be installed for each smoke damper and combination smoke/fire damper to provide access for their inspection and the resetting of the release device. (See Note A-3.1.8.10.(5))
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OBC Div. B 3.1.8.16. Wired Glass and Glass Block
(1)Except as permitted by Articles 3.1.8.18. and 3.1.8.19. for the separation of exits, an opening in a fire separation having a fire-resistance rating not more than 1 h is permitted to be protected with fixed wired glass assemblies or glass blocks installed in conformance with NFPA 80, "Standard for Fire Doors and Other Opening Protectives." (See also Article 3.3.2.17.)
(2)Wired glass assemblies permitted by Sentence (1) and described in MMAH Supplementary Standard SB-2, "Fire Performance Ratings," are permitted to be used as closures in vertical fire separations without being tested in accordance with Sentence 3.1.8.4.(1).
(3)Glass blocks permitted by Sentence (1) shall be installed in accordance with Subsection 4.3.2. and reinforced with steel reinforcement in each horizontal joint.
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OBC Div. B Table 3.1.8.17. Restrictions on Temperature Rise and Glazing for Closures
Table 3.1.8.17. Restrictions on Temperature Rise and Glazing for Closures Forming Part of Articles of 3.1.8.17. and 3.1.8.18. Location | Minimum Required Fire-Protection Rating of Door | Maximum Temperature Rise on Opaque Portion of Unexposed Side of Door, °C | Maximum Aggregate Area of Wired Glass or Safety Glazing in a Door, m² | Maximum Aggregate Area of Glass Block, Wired Glass or Safety Glazing Panels Not in a Door, m² Between a dead-end corridor and an adjacent occupancy where the corridor provides the only access to exit and is required to have a fire-resistance rating | Less than 45 min | No limit | No limit | No limit Between a dead-end corridor and an adjacent occupancy where the corridor provides the only access to exit and is required to have a fire-resistance rating | 45 min | 250 after 30 min | 0.0645 | 0.0645 Between an exit enclosure and the remainder of the floor area in buildings not more than 3 storeys in building height | All ratings | No limit | 0.8 | 0.8 Between an exit enclosure and the remainder of the floor area (except as permitted above) | 45 min | 250 after 30 min | 0.0645 | 0.0645 Between an exit enclosure and the remainder of the floor area (except as permitted above) | 1.5 h | 250 after 1 h | 0.0645 | 0.0645 Between an exit enclosure and the remainder of the floor area (except as permitted above) | 2 h | 250 after 1 h | 0.0645 | 0.0645 In a firewall | 45 min | 250 after 30 min | 0.0645 | 0 In a firewall | 1.5 h | 250 after 30 min | 0.0645 | 0 In a firewall | 3 h | 250 after 1 h | 0 | 0
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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 3.1.9.4. 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).
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OBC Div. B 3.1.9.2. Service Equipment Penetrations
(1)Ducts, electrical outlet boxes, pipes, totally enclosed raceways, optical fibre cables, electrical wires and cables, and other similar service equipment are permitted to penetrate a fire separation or a membrane forming part of an assembly required to have a fire-resistance rating, provided they are protected at the penetration with a firestop conforming to Sentence 3.1.9.1.(1). (See Note A-3.1.9.2.(1))
(2)Combustible totally enclosed raceways that are embedded in a concrete floor slab are permitted in an assembly required to have a fire-resistance rating, provided the concrete cover between the raceway and the bottom of the slab is not less than 50 mm.
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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 3.1.10.1. 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 3.1.10.3. Continuity of Firewalls
(1)A firewall shall extend from the ground continuously through, or adjacent to, all storeys of a building or buildings so separated, except that a firewall located above a basement storage garage conforming to Article 3.2.1.2. is permitted to commence at the floor assembly immediately above the storage garage. (See also Sentence 3.1.10.1.(3))
(2)A firewall is permitted to terminate on the underside of a reinforced concrete roof slab provided
(a)the roof slab on both sides of the firewall has a fire-resistance rating not less than
(i)1 h if the firewall is required to have a fire-resistance rating not less than 2 h, or
(ii)2 h if the firewall is required to have a fire-resistance rating not less than 4 h, and
(b)there are no concealed spaces within the roof slab in that portion immediately above the firewall.
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OBC Div. B 3.1.11.1. Separation of Concealed Spaces
(1)Concealed spaces in interior wall, ceiling and crawl spaces shall be separated from concealed spaces in exterior walls and attic or roof spaces by fire blocks conforming to Article 3.1.11.7.
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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 3.1.11.6. Fire Blocks in Crawl Spaces
(1)A crawl space that is not considered as a basement by Article 3.2.2.9. and in which sprinklers are not installed shall be separated by construction conforming to Article 3.1.11.7. into compartments not more than 600 m² in area with no dimension more than 30 m.
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OBC Div. B 3.1.11.7. Fire Block Materials
(1)Except as permitted by Sentences (2) to (5) and (8), fire blocks shall remain in place and prevent the passage of flames for not less than 15 min when subjected to the standard fire exposure in CAN/ULC-S101, "Standard Method of Fire Endurance Tests of Building Construction and Materials."
(2)Gypsum board not less than 12.7 mm thick and sheet steel not less than 0.38 mm thick need not be tested in conformance with Sentence (1) provided all joints have continuous support.
(3)In a building required to be of noncombustible construction, wood nailing elements described in Article 3.1.5.8. need not be tested in conformance with Sentence (1).
(4)In a building or part of a building permitted to be of encapsulated mass timber construction, wood nailing elements referred to in Article 3.1.6.11. need not be tested in conformance with Sentence (1).
(5)In a building permitted to be of combustible construction, in a combustible roof system permitted by Sentences 3.1.5.3.(2) and 3.1.6.7.(1), and in a raised platform permitted by Sentence 3.1.5.10.(2) or 3.1.6.12.(1), fire blocks are permitted to be
(a)solid lumber or a structural composite lumber product conforming to ASTM D5456, "Standard Specification for Evaluation of Structural Composite Lumber Products," not less than 38 mm thick,
(b)phenolic bonded plywood, OSB, waferboard or oriented strandboard not less than 12.5 mm thick with joints supported, or
(c)two thicknesses of lumber or a structural composite lumber product conforming to ASTM D5456, "Standard Specification for Evaluation of Structural Composite Lumber Products," each not less than 19 mm thick with joints staggered, where the width or height of the concealed space requires more than one piece of lumber or structural composite lumber product not less than 38 mm thick to block off the space.
(6)Openings through materials referred to Sentences (1) to (5) shall be protected to maintain the integrity of the construction.
(7)Where materials referred to Sentences (1) to (5) are penetrated by construction elements or by service equipment, a firestop shall be used to seal the penetration. (See Note A-3.1.11.7.(7))
(8)In buildings permitted to be of combustible construction, semi-rigid fibre insulation board produced from glass, rock or slag is permitted to be used to block the vertical space in a double stud wall assembly formed at the intersection of the floor assembly and the walls, provided the width of the vertical space does not exceed 25 mm and the insulation board
(a)has a density not less than 45 kg/m²,
(b)is securely fastened to one set of studs,
(c)extends from below the bottom of the top plates in the lower storey to above the top of the bottom plate in the upper storey, and
(d)completely fills the portion of the vertical space between the headers and between the wall plates. (See Note A-3.1.11.7.(8))
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OBC Div. A 1.4.1.2.(1) Fire block
Fire block means a material, component or system that restricts the spread of fire within a concealed space or from a concealed space to an adjacent space.
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OBC Div. A 1.4.1.2.(1) Firestop
Firestop means a system consisting of a material, component and means of support used to fill gaps between fire separations or between fire separations and other assemblies, or used around items that wholly or partially penetrate a fire separation.
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