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9.20.6.1.(2)
OH1OS2OP2OH4OS3
ObjectiveOH1 Indoor Conditions
Attribution
[F20,F22-OH1.1,OH1.2,OH1.3] Applies to elements that support or are part of an environmental separator.
Application
Application 1: 
Minimum thickness of above-ground, unreinforced masonry exterior walls:
  • in the bottom storeys of 2-storey buildings and the bottom 2 storeys of 3-storey buildings:
    • where the wall height above the foundation wall does not exceed 11 m, and
    • in which the roof or floor system above the first storey is not of concrete construction, and
  • in buildings of more than one storey in regions where the spectral response acceleration Sa(0.2) is greater than 0.55 that are reinforced in accordance with Sentence 9.20.1.2.(1) and loadbearing masonry exterior walls of 3-storey buildings in regions where the spectral response acceleration Sa(0.2) is greater than 0.35 and less than or equal to 0.55 that are reinforced in accordance with Sentence 9.20.1.2.(2).
This applies in 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 9.20.1.1.(2), which applies to buildings other than described above, or where the masonry is designed for specified loads on the basis of ultimate and serviceability limit states, and
  • Sentence 9.20.6.2.(3), which applies to cavity walls.
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Intent
Intent 1: 
To limit the probability that masonry exterior walls will be unable to resist expected structural loads.
Where masonry units support or are part of an environmental separator, this is to limit the probability of deformation or cracking, which could lead to the excessive deformation, displacement or failure of required environmental separation elements.
This is to limit the probability of:
  • condensation,
  • precipitation ingress,
  • moisture ingress,
  • excessive heat transfer,
  • pollutant ingress, or
  • compromised thermal performance of components intended to resist heat transfer.
This is to limit the probability of:
  • an inadequate control of temperatures in interior spaces, drafts, relative humidity or water accumulation,
  • the generation of pollutants from biological growth or from materials that become unstable on wetting, or
  • deterioration, which could lead to further compromised integrity of environmental separators.
This is to limit the probability of:
  • negative effects on the air quality of indoor spaces,
  • the inadequate thermal comfort of persons, and
  • contact with moisture.
This is to limit the probability of harm to persons.
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