The Ontario Building Code | Top Plates
220.127.116.11. Top Plates
(1) Except as permitted in Sentences (2) to (4), no fewer than two top plates shall be provided in loadbearing walls.
(2) A single top plate is permitted to be used in a section of a loadbearing wall containing a lintel provided the top plate forms a tie across the lintel.
(3) A single top plate is permitted to be used in loadbearingwalls where the concentrated loads from ceilings, floors and roofs are not more than 50 mm to one side of the supporting studs and in all non-loadbearing walls.
(a) not less than 75 mm by 150 mm by 0.91 mm thick galvanized steel, or