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9.27.3.3.(1)
OS2OH1
ObjectiveOS2 Structural Safety
Attribution
Application
Application 1: 
Minimum number of layers of wall sheathing membranes in cladding assemblies to which Subsection 9.27.3. applies [see Article 9.27.1.1. for application of Subsection 9.27.3.].
Exceptions: 
except as stated in:
  • Sentence 9.27.2.1.(1), which applies where it can be shown that precipitation ingress will not adversely affect occupant health or safety,
  • Article 9.27.3.4., which applies where non-wood-based rigid exterior insulating sheathing or exterior insulating sheathing with an integral sheathing membrane is installed,
  • Article 9.27.3.5., which applies where wall sheathing is not installed, and
  • Article 9.27.3.6., which applies where the joints between the sheets of cladding are formed in such a manner that they are unlikely to allow the passage of wind or rain.
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Intent
Intent 1: 
To limit the probability of:
  • excessive air infiltration or “wind-washing,” which could lead to condensation, and
  • precipitation ingress.
This is to limit the probability of the failure of required environmental separation elements, which could lead to deterioration, which could lead to compromised structural integrity of exterior walls, which could lead to harm to persons.
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