Where hollow masonry building-units are used in masonry construction, the following requirements shall be complied with-

a) where roofs, floors or beams bear directly on walls, piers or columns, either-

i) all cavities in the top course of the building -units in the supporting member shall be completely filled with mortar of the same class as that used for laying the units; or

ii) the top course in the supporting member shall be of sold building-units not less than 100 millimetres in height;

b) where a wall of hollow units is decreased in thickness at any particular height, the top course of units of the thicker section shall either be completely filled with mortar of the same class as that used in laying the units or be of solid units not less than 100 millimetres in height;

c) in no case shall a foundation-wall of hollow units be corbelled to carry a thicker wall;

d) in no case shall a wall of hollow units supports a veneer, except in accordance with S.A.B.S. 073;

e) where mortar is spread on the cross-webs, a clear space, free of mortar, not less than 25 millimetres in width, may be left at the centre of each such web to prevent the passage of moisture through the joint.