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9.4.2.2.(1)
OS2OP2OH1
ObjectiveOS2 Structural Safety
Attribution
Application
Application 1: 
Specified snow loads on roofs of light-frame constructions where wall, floor and roof planes are generally comprised of frames of small repetitive structural members, and where:
  • roof and wall planes are clad, sheathed or braced on at least one side,
  • the small repetitive structural members are spaced not more than 600 mm o.c.,
  • the clear span of any structural member does not exceed 12.2 m,
  • the maximum deflection of the structural roof members conforms to Article 9.4.3.1.,
  • the maximum total roof area, regardless of firewalls, is 4 550 m2, and
  • for flat roofs, there are no significant obstructions on the roof, such as parapet walls, spaced closer than the distance calculated by:
    where
    Do
    = minimum distance between obstructions, m,
    Ho
    = height of the obstruction above the roof, m,
    Ss
    = ground snow load, kPa, and
    γ
    = unit weight of snow, kN/m3.
This applies to buildings to which Part 9 applies [see Sentence 1.3.3.3.(1) of Division A for application of Part 9].
Exceptions: 
except:
  • as stated in Sentence 9.4.2.2.(2), which applies to the minimum specified snow load, and
  • as exempted in Sentence 9.4.2.2.(3), which applies to bow string, arch and semi-circular roof trusses having an unsupported span greater than 6 m.
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Intent
Intent 1: 
To limit the probability that inaccurate snow load assumptions will lead to assemblies being unable to resist gravity, snow and rain loads.
This is to limit the probability of compromised structural integrity, which could lead to:
  • structural failure, or
  • for environmental separators or elements supporting environmental separators, the displacement or failure of required environmental separation elements, which could lead to the deterioration of building elements.
This is to limit the probability of harm to persons.
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