Fire separations, door latches and penetrations (Detection, Lighting and Power)

Last updated October 22, 2026

Values this chapter turns on

max outlet box size with no firestop needed: 0.016 m²; max outlet box size with no firestop needed
spacing of outlet boxes on opposite wall faces: 600 mm; spacing of outlet boxes on opposite wall faces
concrete below a combustible raceway in a slab: 50 mm; concrete below a combustible raceway in a slab
max horizontal concealed space in a wall: 20 m; max horizontal concealed space in a wall

For a detection and power examiner, fire separations matter in three places. Hold-open devices are released by the fire alarm system. Every cable, raceway and outlet box that passes through a rated assembly must be firestopped. Concealed spaces need fire blocks. This chapter covers 3.1.8., 3.1.9., 3.1.10.1. and 3.1.11., leaving out the combustible piping sentences the syllabus excludes.

Fire separations, hold-open devices and door latches

A required fire separation must be continuous and carry the rating the Code specifies. Openings in it need closures, shafts or the other protection in 3.1.8., 3.1.9. and 3.2.8. OBC Div. B 3.1.8.1..

Continuity OBC Div. B 3.1.8.3.:

A concealed space above a vertical fire separation must be divided by an equivalent separation, unless 3.6.4.2.(2) applies.
Where a rated separation meets a floor, ceiling, roof or another separation, the joint gets a firestop with an FT rating at least equal to the abutting separation's rating, tested to CAN/ULC-S115.
Joints between floors and exterior walls get a perimeter firestop tested to ASTM E2307.
Gypsum board joints arranged to restrict flame and smoke are exempt.

A "closure" covers the whole assembly: door, shutter, damper, wired glass or glass block, plus hardware, closers, frames and anchors Div. A. Every swing-type door in a fire separation needs a positive latching mechanism that holds it shut after each use OBC Div. B 3.1.8.15..

Hold-open devices

A hold-open device is allowed on a closure in a fire separation OBC Div. B 3.1.8.14., except on:

an exit stair door in a building more than 3 storeys in building height, and
a vestibule door required by 3.3.5.7.

How it must release depends on whether there is a fire alarm and which door it is:

Building and door	Release on
Single-stage fire alarm	Any signal from the system
2-stage fire alarm	Any alert signal, or adjacent smoke detectors
Fire alarm, and an exit door, a door to a public corridor, a closure serving assembly, care, detention or residential occupancy, or a smoke control door	A smoke detector on the fire alarm system, located as CAN/ULC-S524 describes
No fire alarm, same door types (except smoke control doors)	A smoke alarm at ceiling level on either side, within 1.5 m horizontally of the opening
Other closures	A heat-actuated device is acceptable

In a care and treatment occupancy, a door between a public corridor and a sleeping room need not release automatically.

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Penetrations by wiring and services

The base rule: a penetration of a fire separation, or of a membrane in a rated assembly, is either firestopped or cast in place OBC Div. B 3.1.9.1..

Separation	Firestop rating (CAN/ULC-S115)
General fire separation	F rating at least the required fire-resistance rating
Firewall, or a horizontal separation rated under 3.2.1.2.	FT rating at least the separation's rating
Steel, ferrous, copper, concrete or masonry items	May be cast in place instead

Sprinklers may pass through with a metal escutcheon plate per NFPA 13. Fire dampers installed to NFPA 80 need no firestop. Penetrations contained within a wall cavity above and below a rated floor, or within a rated floor or ceiling space, may use an F-rated firestop in place of FT.

Ducts, outlet boxes, pipes, totally enclosed raceways, optical fibre cables, and electrical wires and cables may penetrate if they are firestopped to 3.1.9.1.(1). A combustible raceway may be embedded in a rated concrete slab with at least 50 mm of concrete below it OBC Div. B 3.1.9.2..

Outlet boxes OBC Div. B 3.1.9.3.:

Normally firestopped with an FT rating equal to the separation's rating.
Noncombustible boxes need no firestop if each is not over 0.016 m², the total is not over 0.065 m² in any 9.3 m² of surface, and the annular gap is not over 3 mm.
Boxes on opposite sides of a rated wall must be 600 mm apart horizontally, separated by a fire block, or each firestopped.

Membrane ceilings rated under SB-2 may have duct openings protected as SB-2 describes. Fire stop flaps must conform to CAN/ULC-S112.2 OBC Div. B 3.1.9.5..

Worked example

A rated corridor wall gets noncombustible outlet boxes of 0.012 m² each, with a 2 mm gap at the membrane.

Each box is within 0.016 m². Pass.
How many in a 9.3 m² panel without firestops? 0.065 / 0.012 = 5.4, so 5 boxes.
A box on the other side sits 400 mm away horizontally. That is under 600 mm, so it needs a fire block or a firestop on each box.

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Firewall collapse and fire blocks

Framing connected to or supported on a firewall, with a rating lower than the firewall's, must be designed so that its failure in a fire does not compromise the firewall OBC Div. B 3.1.10.1.. A double firewall avoids this if each leaf is tied to its own frame and carries half the required rating. Piping, ducts and totally enclosed noncombustible raceways must be installed so that their collapse will not bring the firewall down.

A fire block restricts fire spread within or out of a concealed space Div. A. Concealed spaces in interior walls, ceilings and crawl spaces are blocked from those in exterior walls and attics OBC Div. B 3.1.11.1.. In wall assemblies, fire blocks go at every floor, at rated ceilings, and so that no concealed space is over 20 m horizontally or 3 m vertically OBC Div. B 3.1.11.2.. Exceptions include walls filled with insulation, noncombustible materials, materials with a flame-spread rating of 25 or less (then fire blocks every 10 m vertically), or a single air space of 25 mm or less.

Horizontal concealed spaces in combustible floors and roofs without sprinklers are compartmented to 600 m² (60 m maximum dimension) when the exposed materials have a flame-spread rating of 25 or less, otherwise to 300 m² (20 m) OBC Div. B 3.1.11.5.. Fire block materials must hold for 15 min under CAN/ULC-S101. Gypsum board of 12.7 mm or more and sheet steel of 0.38 mm or more are accepted without testing, and any penetration of a fire block needs a firestop OBC Div. B 3.1.11.7..

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Common traps

Putting a hold-open device on an exit stair door in a 4-storey building. Not allowed.
Releasing hold-opens only on the second stage of a 2-stage system. They release on the alert signal.
Specifying an FT rating for an ordinary fire separation penetration. F is the default; FT applies to firewalls and certain horizontal separations.
Confusing 0.016 m² (one box) with 0.065 m² (aggregate).
Forgetting that cables are "service equipment" that needs firestopping.

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 separations, hold-open devices and door latches	A required fire separation must be continuous and carry the rating the Code specifies.
Penetrations by wiring and services	The base rule: a penetration of a fire separation, or of a membrane in a rated assembly, is either firestopped or cast in place.
Firewall collapse and fire blocks	Framing connected to or supported on a firewall, with a rating lower than the firewall's, must be designed so that its failure in a fire does not compromise the firewall.

Fire separations, hold-open devices and door latches
A required fire separation must be continuous and carry the rating the Code specifies.
Penetrations by wiring and services
The base rule: a penetration of a fire separation, or of a membrane in a rated assembly, is either firestopped or cast in place.
Firewall collapse and fire blocks
Framing connected to or supported on a firewall, with a rating lower than the firewall's, must be designed so that its failure in a fire does not compromise the firewall.

Usual exam traps

Putting a hold-open device on an exit stair door in a 4-storey building. Not allowed.
Releasing hold-opens only on the second stage of a 2-stage system. They release on the alert signal.
Specifying an FT rating for an ordinary fire separation penetration. F is the default; FT applies to firewalls and certain horizontal separations.
Confusing 0.016 m² (one box) with 0.065 m² (aggregate).
Forgetting that cables are "service equipment" that needs firestopping.

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Code cited in this chapter

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

OBC Div. B 3.1.8.1. 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))
Open OBC Div. B 3.1.8.1. in the code viewer
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))
Open OBC Div. B 3.1.8.3. in the code viewer
OBC Div. A 1.4.1.2.(1) Closure
Closure means a device or assembly for closing an opening through a fire separation or an exterior wall, such as a door, a shutter, a damper, wired glass or glass block, and includes all components such as hardware, closing devices, frames and anchors.
Open OBC Div. A 1.4.1.2.(1) in the code viewer
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.
Open OBC Div. B 3.1.8.15. 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
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.
Open OBC Div. B 3.1.9.1. in the code viewer
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.
Open OBC Div. B 3.1.9.2. in the code viewer
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."
Open OBC Div. B 3.1.9.3. in the code viewer

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OBC Div. B 3.1.9.5. Openings Through a Membrane Ceiling
(1)A membrane ceiling forming part of an assembly assigned a fire-resistance rating on the basis of MMAH Supplementary Standard SB-2, "Fire Performance Ratings," is permitted to be penetrated by openings leading into ducts within the ceiling space provided
(a)the ducts are sheet steel, and
(b)the number of openings and their protection conform to the requirements of MMAH Supplementary Standard SB-2, "Fire Performance Ratings."
(2)Fire stop flaps in ceiling membranes required in Sentence (1) shall conform to CAN/ULC-S112.2, "Standard Method of Fire Test of Ceiling Firestop Flap Assemblies."
Open OBC Div. B 3.1.9.5. in the code viewer
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.
Open OBC Div. B 3.1.10.1. in the code viewer
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.
Open OBC Div. A 1.4.1.2.(1) in the code viewer
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.
Open OBC Div. B 3.1.11.1. in the code viewer
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.
Open OBC Div. B 3.1.11.2. in the code viewer
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.
Open OBC Div. B 3.1.11.5. in the code viewer
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))
Open OBC Div. B 3.1.11.7. in the code viewer