Above-ground unreinforced masonry, nominally reinforced masonry where vertical joints in adjacent courses are aligned [see Article 9.20.9.1.], loadbearing masonry of buildings of more than one storey in regions where the spectral response acceleration S_a(0.2) is greater than 0.55 that are reinforced in accordance with Sentence 9.20.1.2.(1), and loadbearing masonry of 3-storey buildings in regions where the spectral response acceleration S_a(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), made with cellular (foamed) concrete blocks, in buildings to which Part 9 applies [see Sentence 1.3.3.3.(1) of Division A for application of Part 9]:

• 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.

Exceptions: 

To limit the probability of an inadequate resistance to sulfate attack or stresses resulting from water absorption and freeze-thaw cycling.

This is to limit the probability of:

• excessive moisture transfer through masonry units, or
• deformation or cracking, which could lead to:
  • where masonry units support or are part of an environmental separator, the excessive deformation, displacement or failure of required environmental separation elements, or
  • where masonry is used in chimneys and fireplaces, compromised integrity of chimneys or fireplaces.

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,
• deterioration, which could lead to further compromised integrity of environmental separators, or
• where masonry is used in chimneys and fireplaces, the leakage of combustion products.

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.