In buildings to which Part 9 applies [see Sentence 1.3.3.3.(1) of Division A for application of Part 9], where chases or recesses exceed the dimension and separation limits stated in Articles 9.20.7.1. to 9.20.7.3. [i.e. in general, one third the thickness of the wall in depth and 500 mm in width, in 190-mm-thick walls, 100 mm in depth, 750 mm in height and 500 mm in width, or 4 times the wall thickness apart, measured from centre to centre, and 600 mm away from any pilaster, cross wall, buttress or other vertical element providing required lateral support for the wall], in:

• above-ground, unreinforced masonry walls and nominally reinforced masonry where vertical joints in adjacent courses are aligned [see Article 9.20.9.1.]:
  • 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,
• in regions where the spectral response acceleration S_a(0.2) is greater than 0.55, loadbearing masonry elements of buildings more than 1 storey in building height [see Sentence 9.20.1.2.(1)]:
  • 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 regions where the spectral response acceleration S_a(0.2) is greater than 0.35 and less than or equal to 0.55, loadbearing masonry elements of buildings 3 storeys in building height [see Sentence 9.20.1.2.(2)]:
  • 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 inadequate support of masonry above certain chases and recesses, which could lead to excessive deflection or cracking.

Where masonry construction is required to provide fire resistance, this is to limit the probability of compromised fire resistance of the assembly, which could lead to harm to persons.