(See Note A-3.1.6.3.)
(1)
Except as provided in Sentences (3) to (9), 3.1.6.3.(4), 3.1.6.16.(2) and 3.1.6.17.(2), and Articles 3.1.6.7. and 3.1.6.12., the exposed surfaces of structural mass timber elements conforming to Article 3.1.6.3. shall be protected from adjacent spaces in the building, including adjacent concealed spaces within wall, floor and roof assemblies, by a material or assembly of materials conforming to Sentence (2) that provides an encapsulation rating that
(a)
is not less than 50 min in a building or part thereof constructed in conformance with Article 3.2.2.48. or 3.2.2.57., or
(b)
conforms to the minimum values stated in Table 3.2.2.93. for the applicable major occupancy and building height. (See Note A-3.1.6.4.(1))
(2)
Except as provided in Sentence 3.1.6.11.(1), the material or assembly of materials referred to Sentence (1) shall consist of
(a)
gypsum board,
(b)
gypsum concrete,
(c)
noncombustible materials,
(d)
materials that conform to Sentences 3.1.5.1.(2) to (4), or
(e)
any combination of materials listed in Clauses (a) to (d).
(3)
Except as provided in Sentences (5) and (7), the exposed surfaces of mass timber beams, columns and arches within a suite or fire compartment in a building or part thereof constructed in conformance with Article 3.2.2.48. or 3.2.2.57. or permitted by Article 3.2.2.93. to have a 50 min encapsulation rating need not be protected in accordance with Sentence (1), provided
(a)
their aggregate exposed surface area does not exceed 35% of the total wall area of the perimeter of the suite or fire compartment in which they are located, and
(b)
the flame-spread rating on any exposed surface is not more than 150. (See Note A-3.1.6.4.(3) to (8))
(4)
Except as provided in Sentences (5) to (7), the exposed surfaces of mass timber walls within a suite in a building or part threreof constructed in conformance with Article 3.2.2.48. or 3.2.2.57. or permitted by Article 3.2.2.93. to have a 50 min encapsulation rating need not be protected in accordance with Sentence (1), provided
(a)
all portions of the exposed surfaces,
(i)
face the same direction, or
(ii)
are separated by a horizonal distance of not less than 4.5 m, and
(b)
the flame-spread rating on any exposed surface is not more than 150. (See Notes A-3.1.6.4.(4) and A-3.1.6.4.(3) to (8))
(5)
Except as provided in Sentence (7), the aggregate exposed surface area of mass timber elements within a suite permitted in Sentences (3) and (4) shall not exceed 35% of the total wall area of the perimeter of the suite. (See Note A-3.1.6.4.(3) to (8))
(6)
Except as provided in Sentence (7), the exposed surfaces of mass timber ceilings within a suite or fire compartment, other than an exit and public corridor, in a building or part thereof constructed in conformance with Article 3.2.2.48. or 3.2.2.57. or permitted by Article 3.2.2.93. to have a 50 min encapsulation rating need not be protected in accordance with Sentence (1), provided the aggregate surface area does not exceed
(a)
10% of the total ceiling area of the suite or fire compartment, where the flame-spread rating on any exposed surface is not more than 150, or
(b)
25% of the total ceiling area of the suite or fire compartment, where the flame-spread rating on any exposed surface of a mass timber wall or ceiling is not more than 75. (See Note A-3.1.6.4.(3) to (8))
(7)
The exposed surfaces of mass timber ceilings within a suite in a building or part thereof constructed in conformance with Article 3.2.2.48. or 3.2.2.57. or permitted by Article 3.2.2.93. to have a 50 min encapsulation rating need not be protected in accordance with Sentence (1) or (6), provided
(a)
the aggregate surface area of any exposed mass timber beams, columns and arches does not exceed 20% of the total wall area of the perimeter of the suite in which they are located,
(b)
all surface of the mass timber walls are,
(i)
protected in accordance with Sentence (1), or
(ii)
mass timber walls that are not otherwise permitted to be exposed in accordance with Sentence (5) are protected by a material or assembly of materials conforming to Sentence (2) that provides an encapsulation rating of not less than 80 min, and
(c)
the flame spread rating on any exposed mass timber wall or ceiling is not more than 75. (See Note A-3.1.6.4.(3) to (8))
(8)
Structural mass timber elements in a building or part thereof permitted by Article 3.2.2.93. to have a 0 min encapsulation rating need not be protected in accordance with Sentence (1), provided
(a)
mass timber walls and ceilings within vertical service spaces, public corridors, and exits are protected on the interior side with a material or assembly of materials conforming to Sentence (2) that provides an encapsulation rating of not less than 25 min, and
(b)
concealed spaces are protected in conformance with Sentence 3.1.6.3.(4). (See Note A-3.1.6.4.(3) to (8))
(9)
In a building or part thereof required by Clause 3.1.6.4.(1)(b) to have a minimum encapsulation rating of 70 min, the upper side of a mass timber floor or roof assembly is permitted to be encapsulated by a material or assembly of materials conforming to Sentence 3.1.6.4.(2) that provides an encapsulation rating of 50 min.