844 DON MILLS RD

Timeline

1. Applied

   2025-12-16

2. Issued

   Not available

3. Completed

   Not available

Project description

Alternative Solution In accordance with Article 3.2.2.24. and Article 3.2.2.29., the building must be constructed of noncombustible construction. Article 3.2.2.16. Heavy Timber allows the use of heavy timber in a two storey sprinklered building in the following locations:Roof Assembly (Sentence 3.2.2.16.(1)),Structural members supporting the roof assembly in the storey below the roof (Sentence 3.2.2.16.(2)).Where a roof is intended to be used by an occupancy, Article 3.2.2.13 requires the roof to obtain the same rating as that of a floor assembly. In the case of the DMCRC, the roof requires the following ratings:No rating where the roof is not occupied (approximately 50% of roof), and6)Roof type R4,7)Specialty Furring Wall F-WDP1,8)Specialty Furring Wall F-WDP2,9)Ceiling type C-WD1,10)Exterior columns throughout.The intention is that the mass timber structure be exposed and therefore, not encapsulated in gypsum. Timber elements within exit stairs will be encapsulated to ensure that the flame spread rating of the interior finish is not more than 25, as per Table 3.1.13.2.All timber elements enclosing the exit stair will be encapsulated with two layers of 12.7 mm Type X gypsum.Several mitigating features are proposed to meet the Functional and Objective Statements of the OBC. The mitigating features will provide a performance level equal to or greater than that required by the acceptable solution in the OBC.The summary of mitigating features address the use of mass timber in a noncombustible building.The following mitigating features are provided:1)Sprinkler system increased reliability and density. The sprinkler system will be designed to an increased hazard level in accordance with NFPA 13, ¿Standard for the Installation of Sprinkler Systems¿. The entire building will be designed as an Ordinary Hazard, Group 1 (OH1) rather than a Light Hazard. Thus, the increase will result in 50% greater water delivered to the floor areas,2)Fire resistance rating and encapsulation. Exit stairs that are comprised of timber beams and columns will be encapsulated by two layers of 12.7 mm Type X gypsum. The floor assembly will provide the required 2 hour fire resistance rating where roof is occupied and is above the A3 occupancy.Sentence 3.1.1.6.(1) assigns heavy timber a fire resistance rating of 45 minutes for buildings permitted to be of combustible construction. In order to achieve a fire resistance rating with wood, the term mass timber is used. Mass timber can be assigned a greater fire resistance rating based on various ULC tests.Mass timber is comprised of large timber components such as glue-laminated timber (glulam), structural composite lumber (SCL) beams and columns, and cross-laminated timber (CLT). Mass timber elements have a significant amount of inherent fire resistance due to the large cross-sectional area and relatively slow rate of charring when exposed to combustion.Recently, the OBC has included encapsulated mass timber as a construction option. This requires the mass timber to be enclosed in gypsum or concrete to achieve the appropriate rating for buildings up to 12 storeys in building height.The DMCRC building will incorporate CLT elements that are not encapsulated in the following locations:Mass timber columns are located along the perimeter of the building and within the building. All columns are considered to provide a 2-hour fire-resistance rating, as per the architectural drawings. APPENDIX E contains the fire-resistance rating calculation methodology from CSA O86, ANNEX B.Second floor assembly will incorporate CLT, and concrete topping,Roof deck incorporates timber elements.The following items have been identified to have mass timber elements:1)Floor type FL3 and FL3a, Suspended CLT Floor with Concrete Topping,2)Exterior soffit S-1,3)Exterior soffit S-2,4)Roof type R1,5)Roof type R3, R3a, R3b,