The Ontario Building Code | Masonry Veneer
220.127.116.11. masonry Veneer
(1) Except for masonry veneer where each masonry unit is supported individually by the structural backing, masonry veneer shall be of solid units not less than 70 mm thick.
(2) Veneer described in Sentence (1) over wood frame walls shall have not less than a 25 mm air space behind the veneer.
(3) masonry veneer less than 90 mm thick shall have unraked joints.
(4) masonry veneer shall conform to Subsection 4.3.2. where the masonry units are required to be individually supported by the structural backing.