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Values this chapter turns on
- response time past which limiting distance doubles
- 10 min
- response time past which limiting distance doubles
- min spacing of openings between facing compartments
- 1 m
- min spacing of openings between facing compartments
- soffit zone near a window that needs protection
- 2,500 mm
- soffit zone near a window that needs protection
- line distance where outside members need protection
- 3 m
- line distance where outside members need protection
Subsection 3.2.3. keeps a fire in one building from igniting the next, and keeps a fire in one fire compartment from leaping outside the wall to another compartment of the same building. The first half is about property lines: how much of a wall may be openings and how the wall is built. The second half is about exposure inside one property: walls facing walls, roofs, soffits, canopies and exits.
Limiting distance and area of unprotected openings
The limiting distance is measured at right angles from the exposing building face to the property line, the centre line of a street, lane or public thoroughfare, or an imaginary line between buildings or fire compartments on the same property (definitionOBC Div. A 1.4.1.2.(1) Limiting distanceLimiting distance means the distance from an exposing building face to a property line, the centre line of a street, lane or public thoroughfare, or to an imaginary line between 2 buildings or fire compartments on the same property, measured at right angles to the exposing building face.). The exposing building face is the part of the exterior wall facing one way, from grade to the ceiling of the top storey, or the wall of one fire compartment (definitionOBC Div. A 1.4.1.2.(1) Exposing building faceExposing building face means that part of the exterior wall of a building that faces one direction and is located between ground level and the ceiling of its top storey or, where a building is divided into fire compartments, the exterior wall of a fire compartment that faces one direction.).
3.2.3.1.OBC Div. B 3.2.3.1. Limiting Distance and Area of Unprotected Openings(1) Except as permitted by Articles 3.2.3.10. to 3.2.3.12., the area of unprotected openings in an exposing building face for the applicable limiting distance shall be not more than the value determined in accordance with (a) Table 3.2.3.1.-B or Table 3.2.3.1.-C for an exposing building face conforming to Article… caps unprotected openings as a percentage of the face, using one of four tables:
| Fire compartment | Groups A, (B), C, D, F-3 | Groups E, F-1, F-2 |
|---|---|---|
| Not sprinklered | 3.2.3.1.-B | 3.2.3.1.-C |
| Sprinklered, in a sprinklered building | 3.2.3.1.-DOBC Div. B Table 3.2.3.1-D. Area of Unprotected Opening for Groups A, B, C, D and F, Division 3 Occupancies, %Table 3.2.3.1.-D — Area of Unprotected Opening for Groups A, B, C, D and F, Division 3 Occupancies, % Forming Part of Sentence 3.1.6.9.(5) and Article 3.2.3.1. Exposing Building Face, Maximum Area, m² | Limiting Distance, 0 m | Limiting Distance, 1.2 m | Limiting Distance, 1.5 m | Limiting Distance, 2 m | Limiting… | 3.2.3.1.-E |
Group B appears only in the sprinklered table, which fits the fact that every Group B construction article in 3.2.2. is sprinklered.
Other rules:
- Face area is all wall facing one direction, from finished ground to the uppermost ceiling (3.2.3.2.OBC Div. B 3.2.3.2. Area of Exposing Building Face(1) Except as permitted by Sentences (2) and (3), the area of an exposing building face shall be calculated as the total area of exterior wall facing in one direction on any side of a building measured from the finished ground level to the uppermost ceiling. (2) If a building is divided by fire separations into fire…). Fire separations of at least 45 min let you calculate each compartment alone. In a sprinklered building with an interconnected floor space, each storey of that space may be treated as its own compartment for this purpose, despite the floor openings.
- Slow response. If any storey is unsprinklered and firefighters cannot reach it within 10 min of the alarm, the required limiting distance is doubled.
- Agreements. Owners and the municipality may register an agreement on title that moves the point to which limiting distance is measured.
- Small limiting distance. In an unsprinklered building with a limiting distance of 2 m or less, each opening is also capped by Table 3.2.3.1.-AOBC Div. B Table 3.2.3.1-A. Maximum Concentrated Area of Unprotected OpeningsTable 3.2.3.1.-A Maximum Concentrated Area of Unprotected Openings Forming Part of Sentence 3.2.3.1.(5) Limiting Distance, m | Maximum Area of Individual Unprotected Openings, m² 1.2 | 0.35 1.5 | 0.78 2.0 | 1.88 (for example 0.35 m² at 1.2 m) and openings serving one room are kept 2 m apart.
Construction and protection of exposing building faces
3.2.3.7.OBC Div. B 3.2.3.7. Construction of Exposing Building Face(1) Except as provided by Sentences (3) and (4) and Articles 3.2.3.10. and 3.2.3.11., the fire-resistance rating, construction and cladding for exposing building faces of buildings or fire compartments of Group A, B, C, D or Group F, Division 3 occupancy classification shall comply with Table 3.2.3.7. (2) Except as… and Table 3.2.3.7.OBC Div. B Table 3.2.3.7. Minimum Construction Requirements for Exposing Building FacesTable 3.2.3.7 — Minimum Construction Requirements for Exposing Building Faces Forming Part of Sentences 3.1.6.9.(5) and 3.2.3.7.(1) to (4) Occupancy Classification of Building or Fire Compartment | Maximum Area of Unprotected Openings Permitted, % of Exposing Building Face Area | Minimum Required Fire-Resistance… turn the permitted opening percentage into a wall rating, construction type and cladding type:
| Permitted openings | Groups A, B, C, D, F-3 | Groups E, F-1, F-2 |
|---|---|---|
| 0 to 10% | 1 h, noncombustible construction and cladding | 2 h, noncombustible construction and cladding |
| over 10 to 25% | 1 h, noncombustible cladding | 2 h, noncombustible cladding |
| over 25 to 50% | 45 min, noncombustible cladding | 1 h, noncombustible cladding |
| over 50% | 45 min, combustible cladding allowed (see notes) | 1 h, combustible cladding allowed |
Relaxations:
- The noncombustible cladding rule can be waived above 10% for walls that pass 3.1.5.5. or 3.1.5.6.
- Between 25% and 50% it can also be waived with all of these: a limiting distance over 5 m, sprinklers including attic spaces, and qualifying cladding.
- These construction rules must be met before any opening increase under 3.2.3.12.
3.2.3.8.OBC Div. B 3.2.3.8. Protection of Exterior Building Face(1) Except as permitted by Sentence (3) and in addition to the requirements of Sentences 3.2.3.7.(1) and (2) and where the maximum permitted area of unprotected openings is greater than 10% of the exposing building face, foamed plastic insulation used in an exterior wall of a building more than 3 storeys in building…: above 3 storeys, where more than 10% openings are permitted, foamed plastic insulation in the wall is protected outside. Use 25 mm of concrete or masonry, or a noncombustible material that passes a 15 min wall test. 3.2.3.9.OBC Div. B 3.2.3.9. Protection of Structural Members(1) Structural members, including beams, columns and arches, placed wholly or partly outside the exterior face of a building and are less than 3 m from the property line or the centre line of a public thoroughfare shall be protected from exterior fire exposure by fire protection having a fire-resistance rating not…: structural members outside the wall and less than 3 m from the property line or street centre line need exterior fire protection. Use the interior rating, but at least 1 h.
Exposure between walls, roofs, soffits and canopies
Exits (3.2.3.13.OBC Div. B 3.2.3.13. Protection of Exit Facilities(1) Except as required by Sentence (3) and as permitted by Sentence 3.4.4.3.(1), if the plane of an exterior wall of an exit enclosure forms an angle less than 135° with the plane of an exterior wall of the building it serves, and an opening in the exterior wall of the exit enclosure could be exposed to fire from an…). Where an exit enclosure's exterior wall meets the building wall at less than 135°, openings need protection if they are within 3 m horizontally and less than 10 m below or 2 m above each other. Unenclosed exterior exit stairs use 10 m below and 5 m above. Protection is glass block, SB-2 wired glass or a closure.
Wall to wall (3.2.3.14.OBC Div. B 3.2.3.14. Wall Exposed to Another Wall(1) Except as required by Sentences (3) and 3.2.3.13.(1) or as permitted by Sentence 3.2.3.19.(5), if an unprotected opening in an exterior wall of a fire compartment is exposed to an unprotected opening in the exterior wall of another fire compartment, and the planes of the 2 walls are parallel or at an angle less…). Unprotected openings in two fire compartments whose walls are parallel or meet at less than 135° are kept apart by D₀ = 2D minus (θ/90 x D), and never less than 1 m. D is the greater limiting distance of the two faces, and θ is the angle between them. The wall within D₀ gets the rating of the interior separation. The rule does not apply in a fully sprinklered building, except across a firewall or from an unsprinklered compartment.
Wall to roof (3.2.3.15.OBC Div. B 3.2.3.15. Wall Exposed to Adjoining Roof(1) Except as permitted by Sentence 3.2.3.19.(5), if a wall in a building is exposed to a fire hazard from an adjoining roof of a separate fire compartment that is not sprinklered in the same building, and the exposed wall contains windows within 3 storeys vertically and 5 m horizontally of the roof, the roof shall…). If a wall has windows within 3 storeys vertically and 5 m horizontally of an unsprinklered compartment's roof, that roof has no skylights within 5 m of the wall.
Soffits (3.2.3.16.OBC Div. B 3.2.3.16. Protection of Soffits(1) Except as permitted by Sentences (3) and (4), where there is a common attic or roof space above more than two suites of residential occupancy or above more than two patients' or residents' sleeping rooms in a Group B, Division 2 or 3 occupancy, and the common attic or roof space projects beyond the exterior wall…). A common attic over more than two residential suites, or more than two Group B, Division 2 or 3 sleeping rooms, that projects as an eave needs protected soffits within 2,500 mm of a window or door. Use noncombustible material at least 0.38 mm thick with a melting point of at least 650°C, 11 mm plywood or lumber, or 12.5 mm strandboard or waferboard, extending 1,200 mm each side of the opening. It can be omitted if the eave is fire-blocked off, or if the rooms behind the openings are fully sprinklered.
Canopies (3.2.3.17.OBC Div. B 3.2.3.17. Canopy Protection for Vertically Separated Openings(1) Except as permitted by Sentences (2) and (3), if a storey classified as a Group E or Group F, Division 1 or 2 major occupancy is required to be separated from the storey above by a fire separation, (a) every opening in the exterior wall of the lower storey that is located vertically below an opening in the storey…). In Group E or Group F, Division 1 or 2 storeys that must be separated from the storey above, openings stacked over each other need a canopy projecting 1 m. It is rated like the floor, but no more than 1 h. A 1 m setback of the upper wall or full sprinklering removes the need.
Common traps
- Measuring limiting distance to the far side of a street. It goes to the centre line.
- Entering Table 3.2.3.7. with the openings drawn. Use the maximum permitted percentage.
- Applying 3.2.3.14. in a fully sprinklered building where no firewall is involved.
- Forgetting the 1 m minimum for D₀.
- Missing that care occupancy sleeping rooms trigger the soffit rule, not just apartments.
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.
- Limiting distance and area of unprotected openings
The limiting distance is measured at right angles from the exposing building face to the property line, the centre line of a street, lane or public thoroughfare, or an imaginary…
Usual exam traps
- Measuring limiting distance to the far side of a street. It goes to the centre line.
- Entering Table 3.2.3.7. with the openings drawn. Use the maximum permitted percentage.
- Applying 3.2.3.14. in a fully sprinklered building where no firewall is involved.
- Forgetting the 1 m minimum for D₀.
- Missing that care occupancy sleeping rooms trigger the soffit rule, not just apartments.
Practice this chapter
Questions on Spatial separation and exposure protection (3.2.3), in the exam format, every answer explained and cited to its article. Sign in to start; a free account gets the free questions.
Code cited in this chapter
Based on the official 2024 Building Code Compendium on ontario.ca.
© King's Printer for Ontario, 2024. Reproduced with permission.
OBC Div. A 1.4.1.2.(1) Limiting distance
Open OBC Div. A 1.4.1.2.(1) in the code viewerLimiting distance means the distance from an exposing building face to a property line, the centre line of a street, lane or public thoroughfare, or to an imaginary line between 2 buildings or fire compartments on the same property, measured at right angles to the exposing building face.
OBC Div. A 1.4.1.2.(1) Exposing building face
Open OBC Div. A 1.4.1.2.(1) in the code viewerExposing building face means that part of the exterior wall of a building that faces one direction and is located between ground level and the ceiling of its top storey or, where a building is divided into fire compartments, the exterior wall of a fire compartment that faces one direction.
OBC Div. B 3.2.3.1. Limiting Distance and Area of Unprotected Openings
Open OBC Div. B 3.2.3.1. in the code viewer(1)Except as permitted by Articles 3.2.3.10. to 3.2.3.12., the area of unprotected openings in an exposing building face for the applicable limiting distance shall be not more than the value determined in accordance with
(a)Table 3.2.3.1.-B or Table 3.2.3.1.-C for an exposing building face conforming to Article 3.2.3.2. of a building or fire compartment which is not sprinklered, or
(b)Table 3.2.3.1.-D or Table 3.2.3.1.-E for an exposing building face conforming to Article 3.2.3.2. of a sprinklered fire compartment that is part of a building which is sprinklered in conformance with Section 3.2. (See Note A-3) (See also Article 3.1.18.3.)
(2)The area of the unprotected openings in an exposing building face shall be the aggregate area of unprotected openings expressed as a percentage of the area of the exposing building face in Table 3.2.3.1.-B, 3.2.3.1.-C, 3.2.3.1.-D or 3.2.3.1.-E. (See Sentence 3.2.3.2.(1))
(3)For the purpose of determining the type of construction and cladding and the fire-resistance rating of an exterior wall,
(a)the exposing building face shall be taken as the projection of the exterior wall onto a vertical plane located so that no portion of the exterior wall of the building or of a fire compartment, if the fire compartment complies with the requirements of Article 3.2.3.2., is between the vertical plane and the line to which the limiting distance is measured, and
(b)the area of unprotected openings shall be determined from Table 3.2.3.1.-B, 3.2.3.1.-C, 3.2.3.1.-D or 3.2.3.1.-E.
(4)For the purpose of determining the actual percentage of unprotected openings permitted in an exterior wall, the location of the exposing building face is permitted to be taken at a vertical plane located so that there are no unprotected openings between the vertical plane and the line to which the limiting distance is measured. (See Note A-3.2.3.1.(4))
(5)Except for buildings that are sprinklered, where the limiting distance is 2 m or less, individual unprotected openings in an exposing building face shall be no greater than
(a)the area stated in Table 3.2.3.1.-A, or
(b)where the limiting distance equal to or greater than 1.2 m, the area calculated by
Area =
Area = 0.24[((2 × LD) − 1.2)^2]
where
Area = area of the unprotected opening, and
LD = limiting distance.
(6)The spacing between individual unprotected openings described in Sentence (5) that serve a single room or space described in Sentence (7) shall not be less than
(a)2 m horizontally of another unprotected opening that is on the same exposing building face and serves the single room or space, or
(b)2 m vertically of another unprotected opening that serves the single room or space, or another room or space on the same storey.
(7)For the purpose of Sentence (6), "single room or space" means a room or space that
(a)is not divided by a wall,
(b)is divided by
(i)a wall that extends less than 1.5 m from the interior face of the exterior wall, or
(ii)a partial height wall, or
(c)consists of two or more stacked spaces that are on the same storey.
(8)If a building has any storey that is not sprinklered and firefighting facilities cannot reach it within 10 min of the alarm being received, the required limiting distance shall be doubled.
(9)If the surface temperature on the unexposed surface of a wall assembly exceeds the temperature limit of a standard fire test as permitted by Article 3.1.7.2., an allowance shall be made for the radiation from the hot unexposed wall surface by adding an equivalent area of unprotected opening to the area of actual openings as follows:
A_C = A + (A_E × F_EO)
where
A_C = corrected area of unprotected openings including actual and equivalent openings,
A = actual area of unprotected openings,
A_F = area of exterior surface of the exposing building face, exclusive of openings, on which the temperature limit of the standard test is exceeded, and
F_EO = an equivalent opening factor derived from the following expression:
F_EO = ((T_u + 273)^4)/((T_e + 273)^4)
T_u = average temperature in degrees Celsius of the unexposed wall surface at the time the required fire-resistance rating is reached under test conditions,
T_e = 892°C for a fire-resistance rating not less than 45 min, 927°C for a fire-resistance rating not less than 1 h, and 1,010°C for a fire-resistance rating not less than 2 h.
(10)Unless a closure used to protect an opening in an exposing building face has a protective performance equivalent to that required for the wall assembly in which it is located, an equivalent area of unprotected opening, determined in accordance with the procedures of Sentence (9) shall be added to the greater of
(a)the actual area of unprotected openings, or
(b)the corrected area of unprotected openings.
(11)The required limiting distance for an exposing building face is permitted to be measured to a point beyond the property line that is not the centre line of a street, lane or public thoroughfare if
(a)the owners of the properties on which the limiting distance is measured and the municipality enter into an agreement in which such owners agree that,
(i)each owner covenants that, for the benefit of land owned by the other covenantors, the owner will not construct a building on his or her property unless the limiting distance for exposing building faces in respect of the proposed construction is measured in accordance with the agreement,
(ii)the covenants contained in the agreement are intended to run with the lands, and the agreement shall be binding on the parties and their respective heirs, executors, administrators, successors and assigns,
(iii)the agreement shall not be amended or deleted from title without the consent of the municipality, and
(iv)they will comply with such other conditions as the municipality considers necessary, including indemnification of the municipality by the other parties, and
(b)the agreement referred to in Clause (a) is registered against the title of the properties to which it applies.
(12)Where an agreement referred to in Sentence (11) is registered against the title of a property, the limiting distance for exposing building faces shall be measured to the point referred to in the agreement.
OBC Div. B Table 3.2.3.1-D. Area of Unprotected Opening for Groups A, B, C, D and F, Division 3 Occupancies, %
Open OBC Div. B Table 3.2.3.1-D. in the code viewerTable 3.2.3.1.-D — Area of Unprotected Opening for Groups A, B, C, D and F, Division 3 Occupancies, % Forming Part of Sentence 3.1.6.9.(5) and Article 3.2.3.1. Exposing Building Face, Maximum Area, m² | Limiting Distance, 0 m | Limiting Distance, 1.2 m | Limiting Distance, 1.5 m | Limiting Distance, 2 m | Limiting Distance, 2.5 m | Limiting Distance, 3 m | Limiting Distance, 4 m | Limiting Distance, 5 m | Limiting Distance, 6 m | Limiting Distance, 7 m | Limiting Distance, 8 m | Limiting Distance, 9 m 10 | 0 | 16 | 24 | 42 | 66 | 100 | N/A | N/A | N/A | N/A | N/A | N/A 15 | 0 | 16 | 20 | 34 | 50 | 74 | 100 | N/A | N/A | N/A | N/A | N/A 20 | 0 | 16 | 20 | 30 | 42 | 60 | 100 | N/A | N/A | N/A | N/A | N/A 25 | 0 | 16 | 18 | 26 | 38 | 52 | 90 | 100 | N/A | N/A | N/A | N/A 30 | 0 | 14 | 18 | 24 | 34 | 46 | 78 | 100 | N/A | N/A | N/A | N/A 40 | 0 | 14 | 16 | 22 | 30 | 40 | 64 | 96 | 100 | N/A | N/A | N/A 50 | 0 | 14 | 16 | 20 | 28 | 36 | 56 | 82 | 100 | N/A | N/A | N/A 60 | 0 | 14 | 16 | 20 | 26 | 32 | 50 | 72 | 98 | 100 | N/A | N/A 80 | 0 | 14 | 16 | 18 | 22 | 28 | 42 | 58 | 80 | 100 | N/A | N/A 100 | 0 | 14 | 16 | 18 | 22 | 26 | 36 | 50 | 68 | 88 | 100 | N/A 150 or more | 0 | 14 | 14 | 16 | 20 | 22 | 30 | 40 | 52 | 66 | 82 | 100
OBC Div. B 3.2.3.2. Area of Exposing Building Face
Open OBC Div. B 3.2.3.2. in the code viewer(1)Except as permitted by Sentences (2) and (3), the area of an exposing building face shall be calculated as the total area of exterior wall facing in one direction on any side of a building measured from the finished ground level to the uppermost ceiling.
(2)If a building is divided by fire separations into fire compartments, the area of exposing building face is permitted to be calculated for each fire compartment provided the fire separations have a fire-resistance rating not less than 45 min.
(3)In a building that is sprinklered throughout and contains an interconnected floor space, the area of the exposing building face for the interconnected floor space is permitted to be determined by considering each storey as a separate fire compartment notwithstanding openings through the floor assemblies.
OBC Div. B Table 3.2.3.1-A. Maximum Concentrated Area of Unprotected Openings
Open OBC Div. B Table 3.2.3.1-A. in the code viewerTable 3.2.3.1.-A Maximum Concentrated Area of Unprotected Openings Forming Part of Sentence 3.2.3.1.(5) Limiting Distance, m | Maximum Area of Individual Unprotected Openings, m² 1.2 | 0.35 1.5 | 0.78 2.0 | 1.88
OBC Div. B 3.2.3.7. Construction of Exposing Building Face
Open OBC Div. B 3.2.3.7. in the code viewer(1)Except as provided by Sentences (3) and (4) and Articles 3.2.3.10. and 3.2.3.11., the fire-resistance rating, construction and cladding for exposing building faces of buildings or fire compartments of Group A, B, C, D or Group F, Division 3 occupancy classification shall comply with Table 3.2.3.7.
(2)Except as provided in Sentences (3) and (4) and Article 3.2.3.10., the fire-resistance rating, construction and cladding for exposing building faces of buildings or fire compartments of Group E or Group F, Division 1 or 2 occupancy classification shall comply with Table 3.2.3.7.
(3)Except as provided in Articles 3.1.4.8. and 3.1.6.9., the requirement in Table 3.2.3.7. for noncombustible cladding for buildings or fire compartments where the maximum permitted area of unprotected openings is more than 10% of the exposing building face is permitted to be waived for exterior wall assemblies that comply with Article 3.1.5.5. or 3.1.5.6.
(4)Except as provided by Articles 3.1.4.8. and 3.1.6.9., the requirement in Table 3.2.3.7. for noncombustible cladding for buildings or fire compartments where the maximum permitted area of unprotected openings is more than 25% but not more than 50% of the exposing building face is permitted to be waived where
(a)the limiting distance is greater than 5 m,
(b)the building or fire compartment and all combustible attic or roof spaces are sprinklered throughout,
(c)the cladding
(i)conforms to Subsection 9.27.6., 9.27.7., 9.27.8., 9.27.9. or 9.27.10.,
(ii)is installed without furring members, or on furring not more than 25 mm thick, over gypsum sheathing at least 12.7 mm thick or over masonry, and
(iii)after conditioning in conformance with ASTM D2898, "Standard Practice for Accelerated Weathering of Fire-Retardant-Treated Wood for Fire Testing," has a flame-spread rating not greater than 25 on the exterior face when tested in accordance with Sentence 3.1.12.1.(1),
(d)the cladding
(i)conforms to Subsection 9.27.12.,
(ii)is installed with or without furring members over gypsum sheathing at least 12.7 mm thick or over masonry,
(iii)has a flame-spread rating not greater than 25 when tested in accordance with Sentence 3.1.12.1.(2), and
(iv)does not exceed 2 mm in thickness exclusive of fasteners, joints and local reinforcements, or (See Note A-3.2.3.7.(4)(d)(iv))
(e)the exterior wall assembly complies with Article 3.1.5.5. or 3.1.5.6.
(5)The construction requirements for the exposing building face stated in Sentences (1) and (2) shall be satisfied before increasing the unprotected opening area as permitted by Sentence 3.2.3.12.(1).
OBC Div. B Table 3.2.3.7. Minimum Construction Requirements for Exposing Building Faces
Open OBC Div. B Table 3.2.3.7. in the code viewerTable 3.2.3.7 — Minimum Construction Requirements for Exposing Building Faces Forming Part of Sentences 3.1.6.9.(5) and 3.2.3.7.(1) to (4) Occupancy Classification of Building or Fire Compartment | Maximum Area of Unprotected Openings Permitted, % of Exposing Building Face Area | Minimum Required Fire-Resistance Rating | Type of Construction Required | Type of Cladding Required Group A, B, C, D, or Group F, Division 3 | 0 to 10 | 1 h | Noncombustible | Noncombustible Group A, B, C, D, or Group F, Division 3 | > 10 to 25 | 1 h | Combustible, Encapsulated Mass Timber Construction, or Noncombustible | Noncombustible Group A, B, C, D, or Group F, Division 3 | > 25 to 50 | 45 min | Combustible, Encapsulated Mass Timber Construction, or Noncombustible | Noncombustible Group A, B, C, D, or Group F, Division 3 | > 50 to < 100 | 45 min | Combustible, Encapsulated Mass Timber Construction, or Noncombustible | Combustible or Noncombustible[1][2] Group E, or Group F, Division 1 or 2 | 0 to 10 | 2 h | Noncombustible | Noncombustible Group E, or Group F, Division 1 or 2 | > 10 to 25 | 2 h | Combustible, Encapsulated Mass Timber Construction, or Noncombustible | Noncombustible Group E, or Group F, Division 1 or 2 | > 25 to 50 | 1 h | Combustible, Encapsulated Mass Timber Construction, or Noncombustible | Noncombustible Group E, or Group F, Division 1 or 2 | > 50 to < 100 | 1 h | Combustible, Encapsulated Mass Timber Construction, or Noncombustible | Combustible or Noncombustible Notes to Table 3.2.3.7.: (1) The cladding on Group C buildings within the scope of Article 3.2.2.51. and on Group D buildings within the scope of Article 3.2.2.60. shall be noncombustible or consist of a wall that satisfies the requirements of Article 3.1.4.8. (2) The cladding on buildings or parts thereof conforming to Article 3.2.2.48., 3.2.2.57. or 3.2.2.93. shall conform to Article 3.1.6.9. or be noncombustible.
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OBC Div. B 3.2.3.8. Protection of Exterior Building Face
Open OBC Div. B 3.2.3.8. in the code viewer(1)Except as permitted by Sentence (3) and in addition to the requirements of Sentences 3.2.3.7.(1) and (2) and where the maximum permitted area of unprotected openings is greater than 10% of the exposing building face, foamed plastic insulation used in an exterior wall of a building more than 3 storeys in building height shall be protected on its exterior surface by
(a)concrete or masonry not less than 25 mm thick, or
(b)noncombustible material that complies with the criteria for testing and conditions of acceptance stated in Sentence (2) when tested in conformance with CAN/ULC-S101, "Standard Method of Fire Endurance Tests of Building Construction and Materials."
(2)The criteria for testing and the conditions of acceptance for a wall assembly to satisfy the requirements of Clause (1)(b) are that
(a)the fire exposed area of the wall assembly shall be not less than 9.3 m² and have no dimension less than 2.75 m,
(b)the exposed surface shall include typical vertical and horizontal joints,
(c)the test shall be continued for not less than 15 min and the standard time/temperature curve of the referenced standard shall be followed,
(d)the noncombustible protective material will remain in place and no through openings should develop that are visible when viewed normal to the face of the material, and
(e)the noncombustible protective material will not disintegrate in a manner that would permit fire to propagate along the surface of the test assembly.
(3)The requirements of Sentence (1) are waived for wall assemblies that comply with the requirements of Article 3.1.5.5. (See Note A-3.1.4.1.(1))
OBC Div. B 3.2.3.9. Protection of Structural Members
Open OBC Div. B 3.2.3.9. in the code viewer(1)Structural members, including beams, columns and arches, placed wholly or partly outside the exterior face of a building and are less than 3 m from the property line or the centre line of a public thoroughfare shall be protected from exterior fire exposure by fire protection having a fire-resistance rating not less than that required for their protection from interior fire exposure, as stated in Articles 3.2.2.20. to 3.2.2.93., but not less than 1 h.
(2)Structural members of heavy timber construction, including beams, columns and arches, that are placed wholly or partly outside an exterior face of a building and are 3 m or more from the property line or the centre line of a public thoroughfare need not be covered with noncombustible cladding.
OBC Div. B 3.2.3.13. Protection of Exit Facilities
Open OBC Div. B 3.2.3.13. in the code viewer(1)Except as required by Sentence (3) and as permitted by Sentence 3.4.4.3.(1), if the plane of an exterior wall of an exit enclosure forms an angle less than 135° with the plane of an exterior wall of the building it serves, and an opening in the exterior wall of the exit enclosure could be exposed to fire from an opening in the exterior wall of the building, the opening in either the exterior wall of the exit or the exterior wall of the building shall be protected in conformance with the requirements of Sentence (4) where the opening in the exterior wall of the building is within 3 m horizontally and
(a)less than 10 m below an opening in the exterior wall of the exit, or
(b)less than 2 m above an opening in the exterior wall of the exit. (See Note A-3.2.3.14.(1))
(2)If an unenclosed exterior exit stair or ramp could be exposed to fire from an opening in the exterior wall of the building it serves, the opening in the exterior wall of the building shall be protected in conformance with the requirements of Sentence (4) where the opening in the exterior wall of the building is within 3 m horizontally and
(a)less than 10 m below the exit stair or ramp, or
(b)less than 5 m above the exit stair or ramp.
(3)Except as permitted by Sentence 3.4.4.3.(1), if an exterior exit door in one fire compartment is within 3 m horizontally of an opening in another fire compartment and the exterior walls of these fire compartments intersect at an exterior angle of less than 135°, the opening shall be protected in conformance with the requirements of Sentence (4).
(4)The opening protection referred to in Sentences (1) to (3) shall consist of
(a)glass block conforming to the requirements of Article 3.1.8.16.,
(b)a wired glass assembly conforming to MMAH Supplementary Standard SB-2, "Fire Performance Ratings," or
(c)a closure conforming to the requirements of Subsection 3.1.8. and Articles 3.2.3.1. and 3.2.3.14.
OBC Div. B 3.2.3.14. Wall Exposed to Another Wall
Open OBC Div. B 3.2.3.14. in the code viewer(1)Except as required by Sentences (3) and 3.2.3.13.(1) or as permitted by Sentence 3.2.3.19.(5), if an unprotected opening in an exterior wall of a fire compartment is exposed to an unprotected opening in the exterior wall of another fire compartment, and the planes of the 2 walls are parallel or at an angle less than 135°, measured from the exterior of the building, the unprotected openings in the 2 fire compartments shall be separated by a distance not less than D₀ where
D_o = 2D − ((θ)/90 × D)
but in no case less than 1 m, and
D = the greater required limiting distance for the exposing building faces of the 2 fire compartments , and θ = the angle made by the intersecting planes of the exposing building faces of the 2 fire compartments (in the case where the exterior walls are parallel and face each other, θ = 0 ° ). (See Note A-3.2.3.14.(1).)
(2)The exterior wall of each fire compartment referred to in Sentence (1) within the distance, D_O, shall have a fire-resistance rating not less than that required for the interior vertical fire separation between the fire compartment and the remainder of the building.
(3)Sentence (1) does not apply to unprotected openings of fire compartments within a building that is sprinklered throughout, but shall apply to,
(a)unprotected openings of fire compartments on opposite sides of a firewall, and
(b)exposure from unprotected openings of a fire compartment that is not protected by an automatic sprinkler system.
OBC Div. B 3.2.3.15. Wall Exposed to Adjoining Roof
Open OBC Div. B 3.2.3.15. in the code viewer(1)Except as permitted by Sentence 3.2.3.19.(5), if a wall in a building is exposed to a fire hazard from an adjoining roof of a separate fire compartment that is not sprinklered in the same building, and the exposed wall contains windows within 3 storeys vertically and 5 m horizontally of the roof, the roof shall contain no skylights within 5 m of the exposed wall.
OBC Div. B 3.2.3.16. Protection of Soffits
Open OBC Div. B 3.2.3.16. in the code viewer(1)Except as permitted by Sentences (3) and (4), where there is a common attic or roof space above more than two suites of residential occupancy or above more than two patients' or residents' sleeping rooms in a Group B, Division 2 or 3 occupancy, and the common attic or roof space projects beyond the exterior wall of the building, the soffit, and any opening in the soffits or other surface of the projection located within 2,500 mm of a window or door opening, shall be protected by
(a)noncombustible material
(i)not less than 0.38 mm thick, and
(ii)having a melting point not below 650°C,
(b)plywood not less than 11 mm thick,
(c)strandboard or waferboard not less than 12.5 mm thick, or
(d)lumber not less than 11 mm thick.
(2)The soffit protection required by Sentence (1) shall extend the full width of the opening and to not less than 1,200 mm on either side of it, and shall apply to all openings through the soffit within this limit.
(3)If an eave overhang is completely separated from the remainder of the attic or roof space by the use of fire blocks, the requirements of Sentence (1) do not apply.
(4)The protection required by Sentence (1) for projections is permitted to be omitted if
(a)the fire compartments behind the window and door openings are sprinklered in accordance with Article 3.2.5.12., and
(b)all rooms, including closets and bathrooms, having openings in the wall beneath the soffit are sprinklered, notwithstanding exceptions permitted in the standards referenced in Article 3.2.5.12. for the installation of automatic sprinkler systems.
OBC Div. B 3.2.3.17. Canopy Protection for Vertically Separated Openings
Open OBC Div. B 3.2.3.17. in the code viewer(1)Except as permitted by Sentences (2) and (3), if a storey classified as a Group E or Group F, Division 1 or 2 major occupancy is required to be separated from the storey above by a fire separation,
(a)every opening in the exterior wall of the lower storey that is located vertically below an opening in the storey above shall be separated from the storey above by a canopy projecting not less than 1 m from the face of the building at the intervening floor level, and
(b)the canopy required by Clause (a) shall have a fire-resistance rating not less than that required for the floor assembly but need not be more than 1 h, except as required elsewhere in this Subsection.
(2)Except as permitted by Sentence (3), the canopy required by Sentence (1) is permitted to be omitted if the exterior wall of the upper storey is recessed not less than 1 m behind the exterior wall containing the opening in the lower storey.
(3)The requirements of Sentences (1) and (2) are permitted to be waived if the building is sprinklered throughout.