The Ontario Building Code | Fire-Rated Walls
188.8.131.52. Fire-Rated walls
(1) Steel studs used in walls required to have a fire-resistance rating shall be installed so that there is not less than a 12 mm clearance between the top of the stud and the top of the runner to allow for expansion in the event of fire.
(4) The lower runner required in Sentence (3) shall be cut through the flanges and be bent at each end to extend upwards at least 150 mm and fastened to the adjacent studs.