Ministry of Municipal Affairs
PROPOSED CHANGE TO THE 2012 BUILDING CODE
O. REG. 332/12 AS AMENDED
CHANGE NUMBER:
B-03-01-07
SOURCE:
Ontario
CODE REFERENCE:
Div. B - 3.1.5.5.
DESCRIPTION OF THE PROPOSED AMENDMENT
Revise Article 3.1.5.5. to provide greater clarity regarding the requirements for combustible components that are
permitted for exterior walls of buildings required to be of noncombustible construction.
EXISTING 2012 BUILDING CODE PROVISION(S)
3.1.5.5.
Combustible Components for Exterior Walls
(1) Except as required by Sentence (2), an exterior non-loadbearing wall assembly that includes combustible
components is permitted to be used in a building required to be of noncombustible construction provided,
(a) the building is,
(i) not more than 3 storeys in building height, or
(ii) not more than 6 storeys in building height if sprinklered,
(b) the interior surfaces of the wall assembly are protected by a thermal barrier conforming to Sentence 3.1.5.12.(3), and
(c) the wall assembly satisfies the criteria of Sentences (3) and (4) when subjected to testing in conformance with
CAN/ULC-S134, “Fire Test of Exterior Wall Assemblies”.
(See Appendix A.)
(2) Except as permitted by Articles 3.2.3.10. and 3.2.3.11., where the area of unprotected openings determined in
accordance with Tables 3.2.3.1.B. to 3.2.3.1.E. is required to be not more than 10% of the exposing building face, the
construction requirements of Table 3.2.3.7. shall be met.
(3) Flaming on or in the wall assembly shall not spread more than 5 m above the opening during the test procedure
referenced in Sentence (1). (See Appendix A.)
(4) The heat flux during the flame exposure on a wall assembly shall be not more than 35 kW/m2 measured 3.5 m above
the opening during the test procedure referenced in Sentence (1). (See Appendix A.)
(5) A wall assembly permitted by Sentence (1) that includes combustible cladding of fire-retardant treated wood shall
be tested for fire exposure after the cladding has been conditioned in conformance with ASTM D2898, “Accelerated
Weathering of Fire-Retardant-Treated Wood for Fire Testing”.
(6) The requirements in this Article do not apply where foamed plastic insulation is used in an exterior wall assembly of
a building and the insulation is protected in conformance with Sentences 3.2.3.8.(1) and (2).
A-3.1.5.5.(1) Combustible Elements.
These requirements allow for exterior wall assemblies incorporating combustible elements on buildings of noncombustible
construction. Since the tested assemblies must be representative of actual construction, the performance of the entire
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assembly is assessed with regard to its ability to resist flame propagation up the outside of a building. The thermal barrier
protection limits the impact of an interior fire on the wall assembly.
These requirements, in combination, thus allow for wall assemblies containing both combustible cladding elements and nonloadbearing combustible framing members. These wall assemblies can be used as infill or panel type walls between
structural elements, or attached directly to a loadbearing noncombustible structural system. These requirements, however, do
not waive others specifically intended for the protection of combustible insulation in buildings of noncombustible
construction.
These requirements are predicated upon the assumption that the manufacturing process and field installation procedure are
both carried out under an independent quality assurance program designed to confirm that the product and its application are
consistent with the system as tested.
A-3.1.5.5.(3) Flame-Spread Distance.
The maximum flame-spread distance refers to the distance between the top of the opening and the highest observable
instance of flaming along the wall assembly and thus allows intermittent flaming to a height of 5 m above the opening.
A-3.1.5.5.(4) Heat Flux Measurement.
The heat flux to the assembly referred to in Sentence 3.1.5.5.(3) is the maximum one-minute averaged heat flux measured by
transducers located 3.5 m above the top of the opening. The intent of this criterion is to limit the spread of fire on the wall
assembly to a height of 3.5 m above the opening.
Since the exact location of flaming on the exterior surface of a wall assembly can be influenced by the presence of furring
strips, cavities, etc., in the assembly, which could channel the flame away from a heat flux transducer, sufficient transducers
should be located at any given height to intercept any flaming that could occur along the assembly. The exact position of the
transducers will depend on the location of cavities, joints, studs or furring strips in the assembly.
PROPOSED CODE CHANGE
Revise Article 3.1.5.5. as follows:
3.1.5.5.
Combustible Components for Exterior Walls
(1) Except as required in Sentences (2) and (3) and permitted by Sentence (4), combustible components are permitted to be
used for an exterior non-load bearing wall assembly in a building required to be of noncombustible construction, provided
(a) the building is
(i) not more than 3 storeys in building height, or
(ii) not more than 6 storeys in building height if sprinklered,
(b) when tested in accordance with CAN/ULC-S134, "Fire Test of Exterior Wall Assemblies", the wall assembly
satisfies the following criteria for testing and conditions of acceptance (see Appendix A):
(i) flaming on or in the wall assembly does not spread more than 5 m above the opening (see Appendix A),
and
(ii) the heat flux during the flame exposure on the wall assembly is not more than 35 kW/m 2 measured at
3.5 m above the opening (see Appendix A) and
(c) the interior surfaces of the wall assembly are protected by a thermal barrier conforming to Sentence 3.1.5.12.(3)[2012].
(See Appendix A)
(2) Except as permitted by Articles 3.2.3.10.-[2012] and 3.2.3.11.- [2012], where the limiting distance in Tables 3.2.3.1.B.[2012], to 3.2.3.1.E.- [2012], permits an area of unprotected openings of not more than 10% of the exposing building face,
the construction requirements of Table 3.2.3.7.- [2012], shall be met.
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(3) A wall assembly permitted by Sentence (1) that includes combustible cladding of fire-retardant-treated wood shall be
tested for fire exposure after the cladding has been subjected to an accelerated weathering test as specified in ASTM, D 2898,
"Accelerated Weathering of Fire-Retardant-Treated Wood for Fire Testing".
(4) The requirements of this Article do not apply where foamed plastic insulation is used in an exterior wall assembly of a
building and the insulation is protected in conformance with Sentences 3.2.3.8.(1) -[2012] and (2) - [2012].
Staff note:
The requirements of Clause (b) are based on CAN/ULC-S134-13, "Fire Test of Exterior Wall Assemblies"
as referenced in the 2015 mNBC. They are identical to those included in the 2012 Building Code which
references CAN/ULC-S134-92, "Fire Test of Exterior Wall Assemblies"
A-3.1.5.5.(1) Combustible Components for Exterior Walls.
These requirements allow for exterior wall assemblies incorporating combustible elements on buildings required to be of
noncombustible construction. Since the tested assemblies must be representative of actual construction, the performance of
the entire assembly is assessed with regard to its ability to resist flame propagation up the outside of a building. The thermal
barrier protection limits the impact of an interior fire on the wall assembly.
These requirements, in combination, allow for wall assemblies containing both combustible cladding elements and nonloadbearing combustible framing members. These wall assemblies can be used as infill or panel type walls between
structural elements, or attached directly to a loadbearing noncombustible structural system. These requirements, however, do
not waive others specifically intended for the protection of combustible insulation in buildings of noncombustible
construction.
These requirements are predicated upon the assumption that the manufacturing process and field installation procedure are
both carried out under an independent quality assurance program designed to confirm that the product and its application are
consistent with the system as tested.
A-3.1.5.5.(1)(b)(i) Flame-Spread Distance.
The maximum flame-spread distance referred to in Subclause 3.1.5.5.(1)(b)(i) means the distance between the top of the
opening and the highest observable instance of flaming along the wall assembly; thus, intermittent flaming to a height of 5 m
above the opening is acceptable.
A-3.1.5.5.(1)(b)(ii) Heat Flux Measurement.
The heat flux to the assembly referred to in Subclause 3.1.5.5.(1)(b)(ii) is the maximum one-minute averaged heat flux
measured by transducers located 3.5 m above the top of the opening. The intent of this criterion is to limit the spread of fire
on the wall assembly to a height of 3.5 m above the opening.
Fire tests have shown that flame does not spread on the exterior surface of a wall assembly where the heat flux is less than 35
kW/m2 above the opening.
RATIONALE FOR CHANGE
Problem/General Background
As currently written, the Article does not provide clarity with respect to the details of the testing requirements of
the wall assembly. The proposed change reorganizes the requirements to clarify the application of the testing
requirements.
Justification/Explanation
To provide greater clarity for code users.
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Cost/Benefit Implications
Greater usability for code users.
Enforcement Implications
None.
Who is Affected
Code users.
Objective Based Analysis
Provision
Objective/Functional Statement
Division B 3.1.5.5.
(1)
N/A
(2)
[F02, F03-OP3.1]
(3)
N/A
(4)
N/A
(5)
N/A
OTHER SUPPORTING MATERIALS
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