Thickness of dwarf walls

If the dwarf wall is built of brick and is not over 30 ft. long, it shall be 9 in. thick - if over 30 ft. in length, it shall be 13 1/2 in. thick. If the dwarf wall is of concrete adequately reinforced and not over 30 ft. long, it shall be 6 in. thick - if it exceeds 30 ft. in length it shall be 9 in. thick.