ARCHIVED - 3.4.6.8.(2)

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3.4.6.8.(2)

Application

Intent

OS3


Objective	OS3 Safety in Use
Attribution	[F10-OS3.7] [F30-OS3.1]
Application	Application 1: Curved stairs used as an exit. This applies, in buildings described in Sentence 1.3.3.2.(1) of Division A, to: interior and exterior exits, as stated in Appendix Note A-3.4.6., and exits serving floor areas that are intended for occupancy, including mezzanines as stated in Sentence 3.4.2.2.(1). Application 2: This also applies to: stairways used by the public as access to exits, as stated in Appendix Note A-3.4.6., tents and air-supported structures, as stated in Sentences 3.1.6.1.(1) and 9.10.1.2.(1), stairs in a means of egress from a roof, where a roof is used or intended for an occupant load of more than 60, as stated in Sentence 3.3.1.3.(4), stairways, as stated in Sentence 3.3.1.14.(1), and curved stairs used in exits in buildings to which Part 9 applies [see Sentence 1.3.3.3.(1) of Division A for application of Part 9], as stated in Sentence 9.8.4.4.(1). Exceptions: except as stated in: Sentence 3.1.6.2.(1), which prohibits air-supported structures from being located above the first storey on any building, Sentence 3.1.6.2.(2), which prohibits air-supported structures from being used for classrooms or for Groups B, C, or Group F, Division 1 major occupancies, Sentence 3.1.6.2.(3), which requires air-supported structures to be designed as open floor spaces without interior walls, mezzanines, intermediate floors or similar construction, Sentence 3.3.1.3.(5), which applies to rooftop enclosures, Sentence 3.3.1.14.(2), which applies to service rooms, service spaces and industrial occupancies, Subsection 3.3.2., which applies to assembly occupancies, Sentence 3.3.4.7.(1), which applies to dwelling units, Sentence 3.4.2.2.(2), which applies to mezzanines that: are not required to terminate at a vertical fire separation [see Article 3.2.8.1.], are not intended for an occupant load more than 60, do not exceed the area limits for rooms and suites in Table 3.4.2.2., and have limited travel distances to egress doors or stairs, Sentence 3.4.2.2.(3), which applies to at least half of the required means of egress from a mezzanine if the mezzanine is not required to terminate at a fire separation as permitted by Sentence 3.2.8.2.(1), and Sentence 3.4.7.5.(1), which applies to fire escapes.
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Intent	Intent 1: To exempt curved stairs from the prohibition in Sentence 3.4.6.8.(1) regarding tapered treads, if certain measures are taken. This is to limit the probability that: handrails on each side of the stairs will not be provided, treads in the steps will be improperly designed with respect to uniformity, run dimension and leading edge, and the inside radius of the stairs will be of insufficient dimension. This is to limit the probability of: delays in the evacuation or movement of persons to a safe place in an emergency situation, which could lead to harm to persons, and persons tripping or falling, which could lead to harm to persons.
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