The Ontario Building Code | Installation of Runners
18.104.22.168. installation of Runners
(1) Runners shall be provided at the tops and bottoms of walls.
(2) Runners required in Sentence (1) shall be securely attached to the building at approximately 50 mm from the ends, and at intervals of not more than 610 mm o.c. for interior walls and 305 mm o.c. for exterior walls.
(3) Fasteners used for attachment described in Sentence (2) shall consist of the equivalent of 63 mm nails or 25 mm screws.
(4) studs at openings="http://thehandyforce.com/windows/" title ="Window installer in Toronto">openings and that are not full wall height shall be supported by a runner at the ends of the studs, securely fastened to the full length studs at the sides of the opening.